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Goddamn you are smart. I have so much respect for your intelligence. I'd guess you have a ≥145 IQ. Bc I don't believe anyone else helped you create the conclusion you ultimately came to, & obviously, no one wrote this for you. Both of which are testaments to a very intelligent mind's ability to research & think clearly. Thank you vm for your contributions to my understanding of engineering & physics. Anyway, your writing reminds me of another channel whose writing I find so intelligent as to be elegant, example, describing why perpetual motion machines cannot work: _Without a difference in thermal states from which to establish a flow of energy ..._ _...mechanical work cannot be extracted from the system._ Episode...: _Pulling Energy Out Of Thin Air_ YT Channel: _NEW MIND_ YT specifier: UK8Fw5Zjna0
Why not do a video about the SAAB engine that had variable compression. 1,6 liter, 250 HP and fuel consumption of 4 liters/100 km (58.8 miles/US gallon). It was bought by GM and buried, since it was too efficient, or was it some other reason? I know that they had (at least) one engine up an running at Ring Knutstorp in Sweden at some point.
why not passenger car? most hybrid vehicles have some form of transmission, for as long as generator is of same weight as that transmission system it will be a net benefit.
@@fulconandroadcone9488Constant load and rpm is the exact use case of a range extender engine in a plugin hybrid. This would be perfect for that use case if a manufacturer intended to make enough to justify a specific engine just for plugin hybrids.
This video is spot-on : a really good explanation of the basics, but also some deeper knowledge that is needed to really understand why these "improvements" on the basi cycle never got anywhere. I love the final teaser comments around "what would Otto say about his invention today?" .....I think he would be crushingly proud of that contribution, and in the same way that Mozart would play synthesizers, Otto would really appreciate variable valve-timing, turbos, fully digital control systems etc. Well done!
It wasn't abandoned - I instantly recognized this as a double expansion engine and steam engines in ships were using even triple expansion engines for decades until they got replaced with diesels.
yah this shit has been talked about for decades. Wont go anywhere other than for tiny engines with no torque.... it doesnt work properly. Otherwise someone woudl have built one and produced it. When somthing goes prototype so many times and its just abandoned..... its usually either to soon without the tech or just flawed.
@maxkool1330 its not that it doesn't work, as it worked quite well in steam engines for many decades. The problem with adapting it to ICE applications is higher initial cost, added complexity, and size constraints. Fuel efficiency means nothing if the monetary savings plus some are eaten up in the additional costs to buy and maintain the engine. If you go to any wwii era museum ship and see the engine spaces, youll find a crazily complex mess of pipes and equipment that took dozens of sailors per shift to keep running; the engine room of a moden diesel engine ship has an engine room thats fairly simple and open and requires less than 5 sailors per ship to operate. At the end of the day, the option picked the vast majority of times is going to be the one that leaves the most money in the bank at the end of the day.
@@littlejefe494 Sucks to hear, you know that reminded of the fact we all got microplastics in our balls nowadays, and in our dicks too according to a recent study. related?
exactly. its a 180 year old tech used in 150 years old design, yet it took 150 years for "someone" to do it? retarded!!!! Current ICE designs are still using the first design principles of not using exhaust gasses or optimizing mechancal loads making us waste around 70% of fuel.
You beat me to it! And since ships and trains generally operate at a constant load and speed, the engine can be optimized for those without the offspeed drawbacks mentioned here.
For me an extremely interesting and very well presented video. My father was an aero engineer with RR and DeHavilland, back in war WW1 he was among the first to join the Royal Flying Corps. As a youngster he taught me much about 2 and 4 stroke engines but alas as my feisty years approached ‘life’ took a greater part and so much of what he knew was last. But whenever I would tell him about new advances, at least new to me, he would reply it’s all been tried before !! And he would tell me who where and why it failed, or was successful in some cases. I am eternally indebted to him for his efforts, but I think we may have missed the 5 stroke, but I’ll also bet he knew of the process. Thanks again I will forward to my son, take care
@@ULouOW well, if you count the energy to unalive a person, as it is its inteded use, its very uneficient, as I remember in a war you need about 200kg per person of explosives
Hello from finland. I am mechanical engineer, and I most love your clear explanations and great videos. Most of things are clear for me, but you still can educate me. I am more than happy to learn from you. For example the EGR: I never thought about “dirtyness” in intake manifold caused by piston rings! As you explained it, it was completely clear. Of course Your videos are most relaxing and professional and clear as far as I know. Excellent work!
Engines were NEVER designed to have recirculation exhaust back in the intake thats why old engines last longer than new ones for example old diesel engines last up 1M miles vs DEF engines that may go bad at 30-50K miles same goes for the CATs in the exhaust they get plugged up like an old man with no fiber in its diet 😂
Let us not confuse EGR(Exhaust Gas Recirculation as an emission solution targeting nitrogen oxide), and PCV(Positive Crankcase Ventilation as a solution for combustion products that make their way past the rings, contaminating the engine oil).
17:50 Letting you know... steam turbine technology is just a few years behind ICEs having been invented in 1884. Electric motors were invented in 1832, so they are 192 years old. ;)
Yes but his main point was how ubiquitous ICE engines have been in life for so long. Steam engines came and went. And the electric motor, while invented in 1832, did not become incredibly common until recently.
When I was in college in 2014, a group of 3 of us did a feasibility sudy on this concept. We determined that there was no design goal for which a 6-stroke engine was the optimum solution (terminology we used, but it was the same thing). If power density was desired, a bigger conventional engine is the best choice. If efficiency is desired, a turbocharger or turbine generator (for a hybrid system) on a smaller engine is best. It's a very interesting concept and has the potential to do what proponents claim. But it's just not better than alternatives.
Everything is a compromise and it all comes down to money. I think it would be good for generators or hybrids were it could be run at full power or not at all. Did you look at this? What about a diesel version? Detroit now makes a road truck engine with a secondary turbine that harvests a little extra torque. As a fellow engineer, I'd love to hear your thoughts. (Unfortunately, I got the wrong degree)
Really I think a turbocompound setup is a more viable solution. Takes a lot less space and you can simply disconnect the turbine from the crankshaft at low rpm. Turbocompound system is also something that theoretically you can simply add to an existing engine design, almost like installing a supercharger.
@earlyrobotmind All properly running, road going, gasoline engines burn 22% of the air they intake (the portion that is oxygen). Turbo engines avoid NOx by using intercoolers and lower compression. And the efficiency of turbochargers is often misrepresented.
5:07 Diesel engines don't rev as high because of the flame propagation speed in the cylinder, not because of heavier internals. Top fuel dragster engines rev plenty high, yet they too have heavy internals to cope with the boost pressures.
Right, but dragsters require crazy fuel mixes to achieve those revs. A standard diesel engine will be limited by the weight of the components it's being expected to shift.
Rather massive difference between top fueler stroke length (~4.5 inch) and a diesel engine stroke length (4.88 inch). Or in comparing bore to stroke diesel engines are undersquare while a top fuel dragster engine is oversquare. Longer stroke = more reciprocating component inertia due to higher velocities. If your crank radius is the same then a longer stroke piston has to travel a greater distance in the same amount of time at the same rpm as a shorter stroke engine. And you cannot just increase crank radius due to both the room it would take, lateral forces it would apply to the piston, and you'd have reduced mechanical leverage on the crank. When you get to the really big 'diesels' such as marine engines they use crossheads so the long component of the connecting rod can travel vertically up and down and retain a efficient crank radius.
Also remember: (way back when) Gas pump attendees used to smoke like chimneys while putting gas in your car. However, everyone stopped smoking when the top fuel drag cars were in the shop. Why? Few outsiders know this. Nitromethane - that yummy ingredient in dragster fuel - is a liquid high explosive. It's mixed with methanol in just the right amount to be sent through a fuel system. In some ultra-high-speed videos of dragsters doing dragster things st the Christmas tree, you can sometimes see liquid coming out of their exhaust pipes. It's because the fuel is a high explosive that dragster engines are so heavy. NM... nasty stuff, also glow plug airplane fuel!
No, the internal components of an 11,000 hp top fuel engine are lighter than what's inside my generation one small block 400. The difference is that these parts are made from extremely resilient materials: tungsten, magnesium, and exotic aluminum alloys, which provide strength, and extremely light weight.
That was a wonderful argument and technically correct. Unfortunately these engines are not built based on how fast we want the flame front to propagate. The reason a diesel engine turns slowly is they want it to last a long time there's a lot of other things but longevity can be counted in revolutions or years and if you're turning a lot of revolutions in a minute like a drag racer you have a pretty fractional part of a year that you actually run. That big heavy slow torque engine turning slow, forever is a strong selling point on the industrial market. The drag racer Markets very well to young people who are buying something to last a day.
Good presentation! For automotive engines, the advent of variable valve timing is another thing that makes this concept obsolete. You can emulate the Atkinson cycle when running low revs at part load (and get some "internal EGR" for a NOx emissions benefit) by delaying all of the valve timing events. When the driver wants power, you can shift the valve timing to what's best for power output, and you're not stuck with a fixed set of events or a fixed overexpansion ratio like this concept is. And you can fiddle with the valve timing (among other things) during cold-start warm-up to help the catalyst light up.
The Porsche approach of just using a turbine to turn the energy in the exhaust gas into electricity seems better. That approach naturally deals with the fluctuations and turbines are a well developed low weight way to harness energy.
@@BlacKi-nd4uy The key difference with Porsche's approach (not really theirs as it was obvious but they got it out) is that you *aren't* using the recovered energy to send to the output now but saving it in a battery for later use -- including for running a turbo. That solves the problems about light load -- during that time you let the engine do all the work and store the recovered energy. When you need a bunch of power you have boost w/o lag (the 'turbo' is really an electric motor running ogg battery) *and* you can take that battery power and directly drive electric motor in transmission. -- Those planes used a mechanical linkage w/ crankshaft which meant that if you had enough torque at the rpm already you weren't going to get much benefit especially w a carb and no ECU (no way to cut fuel at a given rpm and let turbo make up during light load). Also there are issues w/ losses involved in needing to sync turbine and crankshaft speed. Electric motors can go after the gearbox and every part can spin at it's optimum rate.
Isn't another reason why the 5 stroke engine did not take off is that fuel injection has allowed 4 stroke engines to effectively reduce the intake/compression stroke by leaving the intake valves open beyond BDC and delaying fuel injection until later in the compression stroke?
As I heard it, the intake valves are left open after BDC because some inlet gas is still moving inwards at BDC - which means that you can increase the inlet charge basically for free. Just after BDC the inlet valves are closed; which creates a shock wave that improves the mechanics of compression. p.s. they did this on carb engines as well.
Yup. That's called "modified Atkinson" or "simulated Atkinson" and it achieves similar results without the fragility of the extra linkages in the genuine Atkinson design. The Toyota Prius and some other hybrids use this valve timing cycle; it was never really viable for cars until hybrids because the torque output is pretty poor, especially at low speeds. The EV system in a hybrid supplies good torque even at rest so the engine's shortcomings are covered.
This is one of the best-organized, best-written, and best-narrated technical videos I've ever watched. Very enjoyable. You have a new subscriber. Thank you.
Funny thing about Otto and Daimler's Verbund Motor, we see the exact same principle used in Mallet (pronounced Mal-lay, not mallet like a hammer) type locomotives. Of course, a steam engine is an external combustion engine, but your working fluid is essentially doing the same thing, expanding to push a piston and produce mechanical work. A common gripe for railroads back in the day was that range was limited by both water and fuel. You can build more water towers along a route to supply more water for your engines, and you need to. Water is safety critical. Without enough water in your boiler, it can explode as the crown sheet of the firebox gets too hot and warps under the pressure. Water is cheap, hook the tower up to a well and pump groundwater in. So long as you have the water rights, you're golden. So thats water solved, how about fuel then? Well, in the early days engines ran on wood here in the US. Wood was everywhere, it was plentiful, and cheap as dirt. Wood isn't very energy dense though, and as engines got bigger and more powerful, they needed more energy dense fuel. More energy density in your fuel means more energy in a firebox of the same volume. This improved things on American rails significantly. Unlike Europe though, the US had and still has long, desolate stretches that can go on for hundreds of miles, so time between fuel stops was a big limiting factor. Furthermore, fuel is expensive. Swiss engineer Anatole Mallet realized that steam was only being allowed to partially expand in the cylinders, and after that, was simply blown out the stack to draw a draft for the fire, keeping it hot. Why waste that energy? He designed a new type of locomitive. They had huge boilers, and massive frames. They were so big, they had to have the frame hinge in the middle so it could bend around corner while the boiler hung over the side. They also had two sets of cylinders, making them compound engines. The first set of cylinders used the high pressure steam, and were towards the rear of the engine. They exhausted to pipes which carried the expanded steam to the low pressure cylinders, which were much larger to account for the already expanded steam and resided at the front of the engine. After being expanded again, the steam was allowed to vent through the stack, pulling a draft just like before. These compound engines saw somewhat limited success, but by the 1920's, were viewed as obsolete by the industry at large, as moving more tonnage at high speed became more important than saving a little on fuel. They did their jobs well, and are an important, if underappreciated part of railroad history. The last surviving American Mallet is Norfolk & Western 2156, and she resides at the National Museum of Transportation in St. Louis, Missouri.
Three key points: 1. The moment you mentioned part-throttle operation, the penny dropped. The science is sobering. 2. The main reason IC engines rules is the energy density of the fuel it uses. It doesn’t matter if you lose 65% when you have a gazillion percent to start with. Looking at you, lithium ion bleh… 3. My best conclusion is that the future lies in hybrid technology. Instead of IC versus Electric, combined these two can make a formidable team.
Except that the other key point you seemed to have missed: do not understimate the importance of simplicity, and the problems with complexity. An EV drive train with li-ion IS the new 4 stroke engine platform. Using the principles of 'the cumulative production of a technology platform and exponentially decreased costs' - i.e. why the 4 stroke engine has been the undisputed winner, means it takes another propulsion platform that is architecturally superior in thermodynamics (check), with a set of sub components that each enjoy benefits of manufactured scale (check). Add in the simplicity, and at that point it only becomes a matter of time that a low enough price and scale results in the displacement of the 4-stroke ICE engine. No doubt, it has had a great run and made a great contribution to humanity. But we also need to accept it, and say good riddance.
Again, reality is far from naive theories. Hybrid cars combine the worst aspects of both worlds and are utterly senseless in practice. With an engine drive train combination which ist 10 fold more efficient compared to ICE technology from the 19th century fuel energy density becomes much less of an issue that you would like to think. Most people are stuck 20 years in the past in their knowledge of EV and this is like 100 years in ICE time.
@@itschrisuphere The complexity of an EV lies in it's battery, ignoring that and focusing on the motors as if they are the only component that matters is ignorant at best and intentionally misleading at worst. An EV, though it may have less moving parts, is not simpler than an engine, even modern ones with all their sensors and emission controls.
@@rock7343except that complexity manufacture is different from part complexity. And having a magnitude fewer moving parts is not something you can ‘hand wave’ away (again, see equivalent analogues for other non 4 and 2 stroke engine types re: this video)
@@itschrisuphere The problem is that lithium battery costs are stagnating and still not at a point where they cover all use cases (low range, slow charging, etc.). EVs currently are more expensive then compareable ICE cars and that wont change unless battery costs go down alot more.
In aviation, we had the turbo-compound designs made in order to harness the remaining energy of the exhaust gases. This also led to very complex and unreliable engines although they actually brought better efficiency. All these have been wiped out by jet engines which are less efficient but far more reliable. And reliability in aviation is by far the key factor.
You mean the r3350 with the power recovery turbines? Like you say i think it made sense that they went out in aeroplanes with the introduction of jet engines and their very superior reliability. But i'd never actually thought about using them in cars before, i wonder if it could be worth a shot seeing as they've stayed with piston engines. Wikipedia's r3350 write up says they managed 20% recovery, but mechanics called them "parts recovery turbines" because of increased exhaust temperature causing dropped valves. But it does sound like this improved with time. I wonder if they could be made to work on a car.
@joecook3223 Yes exactly. I meant the R3350 in its turbo compound version powering the DC7 and the Super Constellations. The Connies were often finishing their flights on 3 engines sometimes 2 !!!. I don't know any implementation of the turbo compound tech on a car engine, but I heard Volvo is using it on some truck engines. Here again, reliability seems to be main problem preventing this solution to be widely adopted.
@@joecook3223 Turbocompound engines in the modern form are the F1 power units but instead of directly transforming the waste energy as work the MGU-H recovers that as stored electrical energy. Compound engines make the most sense for applications with a constant load and rpm, as is the case for planes. In reality these won't work on regular cars because in daily driving there is not enough exhaust energy to be recovered to warrant the extra weight, complexity, and cost. In fact, I think we are approaching the limit of extracting more thermal efficiency from ICEs because the biggest concern these days is getting the catalytic converter up to temperature and emissions regulations are increasingly targeting cold starts (where most of emissions come from in modern cars).
Damn, this guy gives so much hope at the beginning of his video and then tore it down with such ruthlessness at the end that I lost hope on future ICE engines.
Hello, I am German and I have not understood every word but I think I understood the main problems. Thank you very much for these informations. My first idea was the the problem with too low exhaust temperatures so the catalyst can not work without added electrical heating. The main problem is the partial load range. Even on big roads a normal car with 150 hourse power only needs 20 to keep a speed of 60 MpH.
It looks like a supercharged version of this would work well with boats or airplanes, where high rpm cruise is the norm. It will not work with automotive, or motorcycles, which spend a lot of time at no load and low rpm.
Finally, at 2:15, you explained WHY the turbochargers don't take power from engine and use instead "energy that would be wasted otherwise". Until now I didn't get how the presence of a turbocharger wasn't having a bad effect on the rotation of the crankshaft. I was thinking that it was the piston to push out the exhaust gas and therefore anything that wasn't a completely free exhaust pipe I thought was having a bad effect, "slowing" the motion of the crankshaft.
@@Longbowgun Huh? The impeller is spun by flow across it, not by temp difference. Hence a larger downpipe with less restriction can allow for better turbo efficiency. Air temp only matters with cylinder charge. Cooler air means more oxygen which increases the cylinder charge. Like a windmill, higher air speed across the blades the faster it spins. Flow through the impeller is exhaust gas, not intake air. Or im not understanding what your trying to say?
@@jeffco908 You are correct. It's the flow that causes the impeller to spin. At the same time, if you could somehow encase the turbo so that there is zero heat loss, when you measure the temp before and after, there will be a significant drop in temp. Same goes for pressure. These two drops are equal to the energy transferred to the intake side of the impeller. This is an example of the 1st law of thermodynamics. Energy can't be created or destroyed, only transferred from one form to another. In this case, the pressure and temp of the exhaust gas is transferred into the torque of the impeller. The 1st law doesn't stop there. That torque is then transferred into increasing the pressure and temp of the intake air.
Toyota recently said that it teams up with Mazda and Subaru to develop some more ICE engines. I think, Volkswagen said something similar recently too. ICE engine will stay with us for the nearest future, that is for sure.
I would say 50 years at least. Now that companies are making mass market EVs the world sees that they are nonsense and all the hype was just hype. Hydrogen is promising but is still a long ways off. It will take a decade or more to develop a commercially viable hydrogen powertrain and decades more to build up infrastructure. ICE on the other hand is here, well known and tested. We can develop alternative fuels much easier that building hydrogen infrastructure. So considering all of this I would say ICE is here for at least the next 50 years.
But increasingly relegated to niches: high performance, cheap retrofits, novelty, etc. Once a transition (like electrification) gets moving there’s little reason to invest much in the old. I think Toyota believes everyone jumped off a bit early so there’s room for some ICE development still, but I suspect very little. I’ve studied these tech substitution models in several industries and so the math is convincing me. But I get things wrong like anyone.
@@myonen4402 And seasonal work like farming - from harvest to seeding. Spraying and fertilizer spreading could be done without ICE and massive improvement in battery energy density.
@@valtersvasilis yes I also see that an EV with a compact diesel electric generator could constant charge the batteries @ peak thermal efficiency would actually be amazing for me as an electrician because I could literally use my truck as a job site generator
I saw an old steam-powered barge boat on either the Mississippi or Missouri. It used 3 pistons, small where the high-pressure steam went in first, then to a medium and large piston, extracting all the useful work from the steam. I remembered that from 30 years ago when seeing your animation with the low-pressure pistons.
Great video. I really liked your graphic on torque contribution for each stroke. I also liked you explanation of how higher compression ratio increases power. Thanks.
This seem like an ideal engine for an electrical vehicle range extender. As an engine used to charge the batteries you can run it exactly at the optimal rpm and avoid the problems of diminished (or negative) returns at low rpm.
The Atkinson/Miller cycle engines already do the same thing without needing a custom engine block. You can just take a regular Otto engine and change the valve timing and connecting rods.
Uhm... yeah... you are 30 years behind the curve here, guys... you're talking about "hybrids"... except you are getting ALL of the emissions at a 5%- 7% efficiency as you are not actually transferring any combustion energy to the tires... which is why we had the hybrids in the first place; the engine running uses the same amount of fuel whether or not the power hits the road...
@@frontiervirtcharter well, as the exhaust temp would have the be WELL above 212F/ 100C to boil water and you can put your hand in the exhaust flow without getting severe burns... and you can actually SEE water DRIPPING out of tail pipes... I'd say NONE.
What you described are known as multiple expansion engines in naval engineering, and were obsolete 70 years ago. Between the world wars naval warships migrated from the then-common triple expansion engine (you describe double expansion engine) to a better method of harnessing power - steam turbines. During WW2 however as the US ramped up its lend-lease program to expand supplies to Allied forces in Europe (and then even more so once it officially joined the war) this style of engine saw a dramatic resurgence in popularity as its simpler, faster, and cheaper to produce than any of the competing turbine models of its era - keeping in mind that all naval power plants operated by steam power, using some mix of coal (really old ships) or bunker fuel (heavy fuel oil that has to be heated before it can even be pumped) to boil sea water to generate steam which then allowed power via expansion to be leveraged however it was needed. Triple expansion engines work great in naval applications as they can be sized to the application, and the overall scale is so large that entire banks can be brought online or held in standby rather than throttling up or down an individual plant, allowing a ship to simply bypass the performance deadzones that exist as you outlines.
you, um.... are aware that steam turbines are simply multi expansion engines, right? other than single stage delavals, theyre all compounded to a certain degree...
@@paradiselost9946 Since I know the applied naval history I took it as assumed that I understood the operating principle :) Though you’re right, many won’t have that context - that all of these discussions are about century+ old technologies. History may not repeat itself, but it does rhyme :)
Seems the better approach to do this multi stage expansion engine is sticking a turbine connected to the engine's exhaust manifold sending extra power to the crankshaft. A whole lot more compact. I believe some old WW2 planes and some truck engines do this.
@@danieltanuwijaya7675 yes, that technique of essentially using the front stage of a turbocharger mechanically coupled to the crank was also used immediately post-war (not sure it actually made it into combat), though with the rise in jet turbines the days of that technology were extremely limited. The term you’re thinking of is “turbo-compounding” - distinctly not the same as a compound super-turbo-charger (keep in mind that in that era “super” charging meant “mechanically engine driven” while “turbo” meant “driven by a turbine, essentially always in the exhaust”). This works essentially by replacing the compressor end of a turbocharger with direct link to the crank, so that exhaust gases drive the crank rather than increase engine power. I don’t watch Formula 1 but I suspect their mechanical energy recovery unit (or whatever it’s called) works under similar principles.
As an ageing thinker of a more philosophical bent but who couldn't engineer his way out of a paper bag in a life-threatening emergency may I congratulate the maker of this video. Matters ere explained with a straightforwardness and clarity that I find rare. I have subscribed and look forward to seeing more. If engines can be explained to me somebody is achieving something.
I come to this channel for the wrinkles in my brain, but I stay for the delicious diatribes you close the videos out with. 😂 "Don't tell me ICE is dead : Read the room!"
It's actually the EV that is on the deathbed. Tesla has over 67,000 unsold EVs hidden in carparks all over the US, VW is redirecting €60 *BILLION* from EV development back to internal combustion engines, Fiat is retrofitting the 500e with petrol engines because the battery vehicles aren't selling, both GM and Ford are 'scaling back' (read 'stopping') production of their EV Silveraro/F150 Lightning due to 'lack of sales'.... All this in an environment where the commodity prices of the raw materials required to build lithium ion batteries (lithium, cobalt, copper, nickel, manganese, etc) have fallen off a cliff! If it wasn't for 'carbon credits' (please don't get me started on those!), Tesla (the company) would never have gotten off the ground.
I now know how to save ICE cars from the impending EV apocalypse! It’s simple, we return to steam… Add a boiler and turbine to an ICE car’s exhaust system that captures the waste heat and converts it to power. Boom, 100% efficiency achieved! You can mail me my engineering award at your convenience, no rush.
@@davemccage7918Steam engines have even lower thermal efficiencies of ICE engines and ICE engines seldom achieve 35 percent efficiency in real world conditions. Take it for what it is: ICE was an improvement over steam and EV is an improvement over ICE… Don’t believe me? Ask yourself why farms retired their old flywheel powered tools and appliances that were connected to loud and smoky hit and miss engines around the turn of the last century when electricity was brought to rural villages…
Serious thought here - if ILMOR's 5 stroke design only extract the expansion cylinder's benefit at high loads, why not apply the engine to use cases that are near constant high load? Imagine a horizontally opposed version in light aircraft. Four HP cylinders and 2 LP cylinders would fit perfectly in the space for existing boxer 6 designs. Aircraft operate in a narrower RPM band and at higher load than automotive applications. The external turbocharger could be better sized to benefit from ram air and lower exhaust pressure at altitude. A 5 stroke design also mimicks the pinnacle of large piston driven aircraft radials of the 1950s that used turbo-compounding to extract exhaust energy. The Wright R3350 was used in the fastest prop airliners like the Douglas DC-7 and Lockheed Constellation and had exhaust turbines that drove a shaft coupled to the engine crankshaft (instead of an intake compressor wheel).
@@Appletank8 Right, turboprops are higher performance and lower maintenance for commercial and military applications that need higher thrust and/or longer range - cargo planes, small commuters, helicopters, etc. But who is spending half a million dollars to put a Pratt & Whitney PT6 in their Cessna?
@@iamaerix True. As an outsider that just follows aviation out of curiousity, it's amazing that General Aviation seems fine with 70 year old engine technology. The FAA finally just approved unleaded avgas for christ's sake. It's like Lycoming and Continental have a regulatory moat around their business.
My 2021 Ducati XDiavel has 13-1 cr, 4 cams, Desmo valve control of 4 per cylinder and 160hp. The bike is very fast and gets fantastic gas mileage... I'd call that efficiency. Great video by the way!
Ironically in 2003 I was working on a nearly identical engine. I called it the double expansion engine. it worked similar and I agree with most of what you mentioned. The same result can be made from a conventional 4 cylinder in line, where the two middle pistons act as the double expansion part, that would allow for using nearly all stock components. Regarding the low speed vs high speed, this engine would be best suited for hybrid vehicles, with the engine tuned to run only at optimum RPM to charge the battery and/or cruise at hiway speeds.
Thanks for your very informative and entertaining videos. I'm so glad I found your channel about a year ago. Learned so much since then. And you are absolutely right, the era of the 4-stroke combustion engine is far from over. We might get new fuels, or it might be used to power the generator for electrical drive. But I think battery-EVs are the entirely wrong way.
"Let me know when any kind of propulsion technology manages to last 150 years" - well... sail propulsion has lasted thousands of years and is still in use and getting improved. Horse drawn stuff has also been used for thousands of years and and is so stuck in our culture that we still compare our engines to horses by using horsepower as unit.
Just here to let you know - electric motors have existed for longer. Michael Faraday demonstrated circular electrically induced motion in 1821, Sturgeon demonstrated the first practical DC motor in 1832 and by 1838, Moritz von Jacobi built an electric boat that carried 14 people across the Neva river.
@@danieltanuwijaya7675that's actually incorrect. The first electric car was built in the 1880's, but the first electric vehicle prototypes were built as far back as the 1830's.
@@danieltanuwijaya7675you don’t know how a permanent magnet synchronous machine (aka electric motor used by teslas)works, it is more complex than combustion engines, in my opinion
@@lucasv5359 I'm familiar with electric motors and no they are nowhere near as complex as the average car engine (it's magnets on a shaft on a housing filled with copper coils), at least mechanically. They (PMSM motors) do need some fancy inverters and controllers to work but so does a modern engine these days with their ECUs.
I remember reading about this years ago when those articles you mentioned started going around, and I ended up coming to the same conclusions about low-load performance that you did. Efficiency wise, modern Atkinson cycle engines achieve roughly the same goals while allowing companies to use existing engine block designs, just increasing gross compression/expansion while redesigning the intake cam profile to hold the valve open during the first 1/4 of the upstroke to reduce net compression. Much easier and cheaper that way. I do think this type of design does have a couple advantages in terms of reduced parts count versus the standard four stroke engines of comparable size and cylinder count. The engine as built only has two fuel injectors, two spark plugs, and associated wiring/plumbing, versus three or four. The intake manifold only goes to two intake ports, and the exhaust is just a single pipe with no actual manifold needed. One thing the 5 stroke engine can do that I don't think Atkinson cycle engines can is run off of a carburetor; since carbs run entirely off of relative vacuum in the intake manifold, and Atkinson cycle engines push part of the intake charge back into the manifold, I'm led to think that the pressure pulse traveling back up the manifold would interfere with the operation of the carb, and thus the engine itself. I suppose where I'm going with this is that the niche for 5 stroke engines might be for moderately small generators - those all use carbs, tend to run at higher sustained loads, and would absolutely benefit from improved efficiency and the lower exhaust noise. Who's willing to invest the money, though?
Jay Leno talks about technology, how it need to be better on all fronts. It cant be better in some, and worse in others. It has to meet or exceed all expectations, or it just has no hope of catching on. One Idea I just had for this is to maybe make and inverse 2 stroke design. Most engines want to keep exhaust byproducts out of their crankcase. However, if you could channel the escaping exhaust gasses to help drive the piston up on the compression stroke, and have it escape naturally out the crankcase, you could achieve a similar effect to a 5 stroke design. A few problems I see with this though all pertain to oil. The first being, how do you keep oil in the motor. If you vent it into the crankcase, its going to blow the oil out through the exhaust. Next would be oil life. You are going to introduce exhaust byproducts into the oil, reducing its lubricity. You will also heat up the oil leading to further oil degradation. Alas, I think the problem lies outside the engine entirely. In the titanic, the triple expansion engines would utilize the steam to its entirety... or not. After leaving the triple expansion engines, the steam would continue to go through a turbine. Turbines have several advantages and disadvantages, one being that they are not ideal for fast acceleration. However, if you could mount your turbo charger to the front of the engine, and have it couple to the engine via the serpentine belt, you can gain a lot of advantages. By having the turbo essentially coupled to the crank, you can have something that can add power to the engine. As its going down the road, it can add rotational energy through the belt and assist the engine by using expended exhaust gasses. By doing so, you also relieve the engine of the load that is typically transcended by the serpentine belt. I love watching Engine Masters on Motor Trend, no Discovery. One on episode, they wanted to see just how much power you were losing to your accessories. They saw 40 horsepower depart the system just by driving an alternator, a water pump, and a radiator fan. Now add in all the extra crap that manufacturers have bolted on, such as Air Conditioning, Power Steering and the added load of the Alternator, and you can probably see losses nearing 100 horsepower in some applications. I say nearing, and every situation is different. That turbo charger belt can effectively remove that load and add power to the engine in the same stroke.
Not sure why you think you can get 100HP out of a turbo or why you wouldn't gear it directly to the crank. The accessory drive on a car engine is not a very efficient way of transmitting power or torque. it is literally designed to slip so that a seized alternator doesn't take out the whole engine. What you are referring to is a turbo compound engine and it has already been done in aviation. It was a stopgap measure that wasn't used for long because turbine engines were superior in every way. It would be a great way to make a cost-prohibitive car engine that would be unreliable. The Wright 3350 used in the B-29 spent far more time in the shop than they did in the air.
@Lurch-Bot so, what I'm talking about is not a force induction engine. it would continue to be naturally aspirated. you could make it turbo charged, but I don't think that would be ideal. my idea of using the serpentine belt is strictly for maintenance purposes. I don't like the idea of having a solid coupling to the crank. having the serpentine belt would make maintenance easy, as you could have a new belt installed relatively easily as compared to something like a chain or gear drive. as far as the 100 horsepower, I don't know what realistic expectation I could have for power output from a turbine off the exhaust. it would obviously be displacement dependent as a 350 v8 would probably give more exhaust resources than a 3800 v6. I don't know to what exent you could get, but for kicks and giggles, let's say on my classic truck, I flip the manifolds over and mount a turbo in line with the serpentine belt and have twin turbines driving the serpentine belt connected to my crank. my engine currently makes about 300 horsepower. I believe, while maintaining naturally aspirated, I could make it have 350-400 horsepower. i would probably upgrade the belt from a 6 spline to an 8 spline, but that's relatively inexpensive
I'd like to imagine him (like a few others) being like "Wait, you still haven't come up with a better idea yet after that long? What are you waiting for?"
@@artysanmobile I mean electric propulsion predates petrol engines and has never stopped being used in one way or another either. Just not in personal cars primarily.
@@tonymorris4335 Toyota is the current boss in hybrid technology, which I believe will be necessary forever. What they are doing with gear-sets replacing a belt is absolute genius.
Generally speaking, the surer path to heat efficiency is bigger cylinders, fewer of them, and slower speeds. In the late 50s/early 60s Deere were building a huge 2-cylinder engine for its larger tractors that set efficiency records that wouldn't be broken for 16 years. So instead of building buzzy little 4s, maybe we should be focusing more effort on 3s and even 2-cylinder engines for powering the ICE side of PHEVS. Soft motor mounts absorb the worse vibes of low cylinder counts and the hybrid system takes care of everything else.
Exactly. There are practical limits to cylinder size depending on application but for gasoline road passenger vehicles the optimum is somewhere in the 600cc to 800cc range. The ONLY reason you see so many vehicles with 2.0L inline 4's is due to various government laws. The USA fortunately doesn't have these so 2.5l is common here. Below 4 cylinders there are other tradeoffs that generally result in a poor design for vehicles so they just shrink the cylinders. There's plenty of straight 6 trucks on the road with large bores. They're heavy but they're very efficient! It works for trucks. Then look at what they use in freighters and cruise ships. Big, slow, and 50% efficient. That's about the best efficiency this world has to offer with regard to practical heat engines.
Or you could just build a Boxer 2 with fork and knife crankpin/connecting rod setup. Better yet, since torque twist becomes increasingly violent with displacement, you could use a U configuration U2 engine with two single inline engines with their crankshafts spinning in opposite directions and connected by 1:1 gears with a 0 phase difference in stroke cycles which gives 0 torque twist, and if you move the cylinder and the cylinder head up by the length of the stroke and connect the two piston heads from below the cylinder into a single entity, you can eliminate the friction made from the pistons heads pushing into the cylinder wall, since the unified set of pistons is receiving a net 0 force from the conrods spinning in opposite directions. The crankshaft balance weights completely cancel out the forces at TDC and BDC and the two balance weights cancel each other's side to side movement as well, though the secondary vibrations still remain since the weights are traveling in circles and the pistons in lines.
Great video! I loved the explanation of how increasing the compression ratio improves thermodynamic efficiency. I couldn't help but notice that this 5-stroke concept is very similar to the triple-expansion piston steam engine with its 3 cylinders used to extract more energy from the steam than a single cylinder. This was the most efficient incarnation of the piston steam engine before it was made obsolete by steam turbines with their higher efficiency and simpler design.
It is sad to see an innovation like this just not pan out into mainstream. The Wankel was along the same lines. It turns out, with mass production, you cannot really beat an inline 4 stroke engine with a small turbo pumping known quantities of air pressure into a computer controlled fuel injected engine to be able to produce desired torque at RPM.. All while complying with US California emission restrictions. EVs will take over eventually, the ICE project was such an amazing and wild ride. I loved the whole progression.
"you know, stuff like... twice the balls, half the hair" 😂 I literally Laughed so hard I shot coffee out of my nose at that line! And the commentary at the end was brilliant, thanks D4A!
@@devilsoffspring5519 As an Engineer that works with other engineer's, there are not many with common sense. Many are copy/paste and have no idea what they are doing
Most modern engines already do this "fifth stroke" by the use of a turbocharger, the exhaust turbine extracts energy from the hot exhaust gases which gets transferred into positive intake pressure which pushes down on the pistons during the intake stroke, does the same thing. Plus of course you can change the operating parameters of the turbo on the fly, from low boost operation using only the expansion energy and increasing engine efficiency, to high boost operation for a large increase in torque on demand (at the expense of efficiency via an increase in exhaust backpressure, but you can't have everything). Heavy Diesel engines have also used an exhaust turbine to add torque directly to the transmission exactly the same way. It's just much simpler to fit a turbine to the exhaust than add an extra cylinder to the block just for this second expansion.
@@seriouscat2231 Get a book in thermodynamics that gives you the equations for various cycles which allows you to calculate the indicated work done. Of course this isn't something you can learn in one afternoon, people get masters degrees on this stuff. Then you have to factor in mechanical losses. Those are very hard to calculate and you'll mostly just have to look up empirical tables of typical figures. OEMs just use FEA computer software that tells you everything about an engine's performance with pretty high accuracy. These are expensive and difficult to learn in their own right.
Makes me think the best 'enhancement' of the 4 stroke engine ever designed was actually Honda's Variable Valve Timing. Rather than 're-inventing the wheel', Honda very wisely took one single aspect of it and applied new thinking (and technology) to produce something genuinely useful. Honda truly is a visionary company.
Fiat were the first manufacturer to develop VVT. Obviously there are lots of different systems to achieve the same basic result and Honda's version is unique but certainly not the revolutionary leap forward you seem to be making it out to be.
@@carloslara7452 honda perfected it 1st. They have insane engine designers. Look at the s2000 engine.... for its time crazy engine. My perfect car would be a toyota build with a honda drive train.... but not sure abouyt the transmissions.... honda trannys are a bit weak.
Can you cover the adiabatic engine built by Dale‘Smokey’ yunick. Thermal efficiency was purportedly higher than today - could be bogus but it would be nice to see what you unearth on the subject. Thank you D4A !😊
It wasn't quite as unsuccessful as we might think. Steam engines. First conceived perhaps a century before Otto's idea, it started actually being commonly used around the same time and may have been where Otto got the idea. That continued for a very long time in ships slowly being phased out around WW2 for the far more powerful turbine engine and/or diesel. Triple expansion was likely the most common method, but it works exactly like this engine here. A high pressure initial cylinder, that expands to a larger lower pressure cylinder, again expanding in the final cylinder before being exhausted often at around atmospheric temperature. The benefit was the same too - efficiency. It was remarkably successful and has obviously demonstrated that the idea has merit if the size and weight allows. Maybe we will continue to see such engines in heavy diesels like semi trucks where the size and weight is a small fraction of the total vehicle and trailer, where fuel costs are an important financial factor, and where high load constant RPM conditions make up a high proportion of usage. We have to hurry though, in a only a couple of years the multiple expansion piston engine will be 250 years old!
@@nathangamble125 No, it's my own. I'm a physicist so I tend towards detail oriented comments. Plus I've obviously got an interest in engine technology and engineering in general.
I wonder if that kind of extra cylinder(s) would make sense on ship diesel engines. I'd imagine those run most of the time at specific rpm so you can design for that specifically. Ship diesel engines are 2-stroke engines so I guess with extra cylinder(s) they would be 3-stroke rather than 5-stroke, but still.
Love this guy!!! The Verbund motor sounds like an analog to the double and even triple expansion steam engines (piston, 2 stroke). Exhaust steam from the small diameter, high pressure cylinder flows into a larger diameter, low pressure 2ndary cylinder. Of course, steam engines tend to be run at a rel constant speed.
35% sounds like a low efficiency, but the average power plant runs on the Rankine cycle and gets 30% - 35%. Most of the power used by EVs comes from Rankine cycle plant. The state of the art for proven heat engine performance is the combined cycle. Rankine cycle dates back to 1859, or 165 years ago. Coal plants, gas plants, nuclear plants and part of combined cycle plants are burning and churning out power with this tech. Also - I drive a 2021 Tacoma with a 6-cyl Atkinson engine. With the right tires and 100% gasoline I can get 26+mpg. As a side note - when engine stats are quoted I always wonder if the engines were fed 100% gasoline or ethanol contaminated gasoline.
This is a peak efficiency, only achievable at low RPMs and full throttle. This is one of 2 main reasons diesel engines are more efficient than petrol ones - they don't need a throttle and can instead reduce the amount of fuel being injected. Petrol engines cannot ignite a mix that is too lean, so they need some kind of air flow restriction.
Have you done a video about ceramic cylinder coatings by any chance? May be interesting to know why despite the great promise it went nowhere. Thanks for your super interesting and well-researched videos!
Ceramic is hard and can withstand high temperatures but it's also very fragile, so vibrations, big changes of temperature in short time, impacts, etc, can break it in little time making it unsuitable for production engines.
Wasn't it used on BMW cylinders as surface finishing? I much prefer the chromium based ones anyway. I've used those since when I was a kid on my 2 stroke bikes...
Were you thinking of Nikasil maybe? I don't think that was ceramic based? Anyway the (promised) ceramic advantage was much less heat transfer to the block. I think there was even talk of ceramic (coated) pistons too.
@orapasc I'm watching from an android tablet with an oled screen. I don't have a reduced white point setting, but I do have the option extra dim on. Even like this, modern oled screens like mine also have a very low refresh rate in low lighting settings, which gives some people head akes and perturbs sleep. I dont have any of the symptoms, but even at the lowest lighting, I still find the background annoying. I think only Oneplus screens from the latest generation on tablet and flagship phones have a high refresh rate, which is said to help with low lighting watching comfort. Oneplus is a fairly common brand, but it's not Samsung or Apple. So their products are rare and have quirks to them(thats why I don't have any them). This is a simple issue that can be fixed in post while editing the video by changing the shade of the background.
Couldn't agree with you more. But we are where we are. If I remember correctly, 60% of US car journey are under 6 miles, 95% under 31. But everyone wants to be able to drive literally all day without stopping, or to take a multi ton electric truck to buy a bag of oranges or drop Johnnie off at school. America has emitted more CO2 than the combined populations of China, India and Japan. And exports more oil than Saudi Arabia produces.
Similar to what Thomas Edison said, we didn’t fail to make an engine. We learned how not to make an engine. Every step for the last 150 years, whether proceeded or not has left us with very powerful engines at very reduced emissions in smaller sizes.
Because it's already a thing and it's called an alternator but it runs on the serpentine belt instead of exhaust gas. The exhaust turbine one already exists and that is called a turbocharger! It doesn't generate electricity but makes an extra boost for the engine which creates more power.
@@Kelle128 "makes an extra boost for the engine which creates more power." NO IT DOES NOT. The additional fuel you can add as a result of the increased volume of O2 is what increases the power. NOT the turbocharger.
25:30 I wasn’t going to mention it but the electric motor was invented in the 1830s…. What has changed recently isn’t the motor as much as the batteries to store the energy and the power electronics to drive them more efficiently.
Misleading. Brushed electric motors were invented in the 1830s, and are still common; but most electric cars use brushless motors, which were invented in the 1960s. The design of both batteries and motors (at least for the types of motors used in the majority of electric vehicles) have fundamentally changed since the 19th century, while the design of 4-stroke engines used in the majority of ICE vehicles has not (unless you count direct injection as a fundamental change, but that dates back to the 1920s so is still much older than brushless motors).
The electric motor has seen some massive improvements like brushless designs, but the original design is still used in a lot of cases. The electric motor is FAR more versatile than combustion engines. But if I can I will usually choose a combustion engine over an electric motor.
@@nathangamble125 brushed motors were not as common as we'd think, brushless is quite old as well and far more common in the industry, once we adopted alternative current as a standard it was cheaper and easier to produce synchronous brushless motors.
@@nathangamble125 Commutator free asynchronous motor was invented 1887, that tech is also quite old it just so happens when they figured out the physics of it they could not quite make it happen with tech they had. What most electric cars happen to use is permanent magnet synchronous motor, you could not use that without DC to AC converters with variable frequency, which would say biggest hold back was electronics for currently used motor as it just so happens they wont start on there own and 100kW is no small amount. Not to mention and when talking about induction motors they are about 90% efficient, so the jump to synchronous motor at best is 10%. And brushed motor goes at 75%, so truly what has changed the most is batteries and electronics. Oh and don't forget all the improvements ICE got from electronics. And still to this day what holds electric cars back is batteries.
Verbundmotor with an additional turbine at the end also saw wide commercial use in the early 20th century, yet modern ships don't use them. Tubo-diesel engine have just become to good.
0:00 🚗 Internal combustion engines are not very efficient, with modern gasoline engines averaging around 35% thermal efficiency. 0:51 📉 The inefficiency stems from all engine strokes being of equal length, with only the combustion stroke producing significant energy. 3:01 📈 Increasing the compression ratio can enhance engine efficiency by allowing more time for energy harnessing during combustion. 7:12 🔄 The Verbund Motor utilized in the past added a fifth stroke, "extended expansion," using exhaust gas energy to boost torque. 9:11 🏎 Ilmor Engineering, known for high-performance engines, developed a five-stroke prototype showing promising fuel efficiency and power. 13:12 ⚖ The five-stroke engine faced challenges with varying exhaust gas energy levels at different engine loads, impacting efficiency. 15:54 🌱 Despite its potential, the five-stroke engine struggled with emission standards due to slower catalytic converter heating. 16:43 🕰 The conventional four-stroke engine has persisted for 150 years, resisting many attempts at disruption due to its reliability and efficiency.
15:17 okay but it does depend on number of cylinders firing, right? Modern engines run on reduced number of cylinders when power output is low. Passive cylinders could even act as those exhaust receivers actually.
2:59 Indeed, if this were not true - that is, if the piston was responsible for pushing out the exhaust - two-stroke engines could not exist. I hadn't really thought of it this way until now but yep
And two-stroke went away, for vehicles, as you have to inject the lubricant (oil) in with the fuel which leave all kinds of extra nasty shit coming out of the exhaust pipe... But that Kawasaki "Two Stroke Screamer" was scary fast and powerful... friggen accidentally pulling wheelies in 4th gear...
@@garrettmasarik8012 given the technical nature of the channel someone (so might as well be me) will probably point out that while almost all two-stroke designs also require oil either premixed or injected, this isn't inherent to running a two-stroke cycle. It is possible, and done in rare designs, to run a two-stroke cycle and also have an actual oil system such that the fuel can be just fuel. I'd enjoy very much a video on the topic to round out my limited understanding. Afaik the main reason this "couldn't" be done is two strokes allow for ports which don't decline in performance under dirty combustion (which two strokes seems to inherently involve, oil or not?) like valves with their tight tolerances. And, I guess, we could probably do a pretty sweet job designing one to work great now, even with an oiling system and valves, but emissions regulations make it so niche it's unlikely to get worked on. I am extrapolating a lot here and I'd love for the channel itself to touch it
@@JoshWalker1 Exactly. The reason most 2-strokes need oil injected with the fuel is that they are using the crankcase as a supercharger. Put an external supercharger on it and you can have a sealed crankcase just like any 4-stroke. A modern sealed crankcase direct-injection 2-stroke could potentially be a very useful engine, and just as clean as any 4-stroke.
Every 4 stroke motorcycle engine I’m aware of opens the exhaust valve way before bottom dead centre on the power stroke, so wastes some of this stroke, presumably sacrificing efficiency for maximum power. My Triumph opens its exhaust valves 43° before BDC. If I recall correctly after 50 years, my Ducato Desmo 450 motorcycle opened its exhaust valve 90° before BDC. It seemed remarkable then, and now. Separately, the compression depends not only on the compression ratio, but also on when the intake valve closes. My Triumph, with 12.92 nominal compression ratio, runs on 91 octane standard unleaded (in Australia). The previous model with a lower 12.25:1 compression ratio requires premium 95 or 98 octane. I think this is because my bike has different valve timing, with later intake valve closing on the compression stroke. IanB
I'm no engineer, but I wonder if cylinder deactivation on the middle cylinder would improve low RPM efficiency. Add a secondary air system to warm up the cats and maybe this would be a feasible design 🤔
As far as cylinder deactivation, I was thinking the same thing. Maybe use a similar concept to variable valve lift and shut down the low pressure cylinder, or at least limit its travel, with hydraulics and/or solenoids.
I was thinking of giving the middle cylinder a fuel injector that only operates at low rpm. Something to give it just enough extra combustion to justify its weight until the outer cylinders are making enough pressure for the middle injector to shut off.
Cylinder deactivation would do nothing as there are no pumping losses in the 3rd cylinder, only gain. The friction is what you want to reduce and for that you'd need to physically disconnect the piston/rod from the crank. Ain't happening in any reasonably efficient way.
The details vary on when you think commercial use started but electric motors and four-stroke engines have been used commercially for about the same amount of time. The future, as they say, is in the details.
Congratulations, great job in investigating rare topics and very instructive in its presentation. May I suggest a video on Miller cycle engine, I heard of it, Mazda and Toyota once used these, I’d loce to hear more. Thanks so much for your great work
As usual, you have a marvelous delivery, & always deliver a well spoken technical description of your subject. Thank you for your delightful & informative video. I never fail to learn SOMETHING from your treatise. Cheers! from the windswept Prairies of Alberta Canada.
There's no replacement for combustion. So long as there is no true evolution in other technologies (wich doesn't exist until companies see a real profit and even then they do the bare minimum and try to force it on the market, instead of making something usefull and effective) there will be nothing else to replace a running, reliable, efficient system. People always talk about how inefficient a combustion engine is pointing out heat loss, but they fail to mention that a 1.000kg car can travel 500-700 km before refueling for 2 minutes, while staying reliable in any weather conditions. Also people like to ignore the fact that combustion engines continue to become more efficient. For the moment being, any alternative to gasoline or diesel is simply a marketing gimmick of a fun, expensive, hobby-technology, that is not suited for real world daily use.
I think it would be better not to split expansion phase on two cylinders, but separate intake and compression to separate cylinder. So one smaller and cold cylinder makes intake and compression and then pushes the compressed air to another one where it burns and expands. That will give a lot of benefits because fresh air will not heat up from the cylinder walls before burning. In the same time expansion cylinder can be much hotter, that reduce the thermal losses. Also intake piston can be made lighter as it works with lower pressure, that will decrease the mechanical losses. Or it even may be replaced with another kind of compressor, like rotary, connected to the crankshaft with a variator to control the power instead of a throttle. The only problem is to push the compressed air from one cylinder to another fast enough. So that might limit the RPMs. Or we need to close the exhaust valve and start exchange the new air earlier, that means there will be still a lot of exhaust gases. But that is good for NOx reduction.
I place my bet on a electro dynamic turbo/compressor which doesn't use exhaust gasses or is belt driven. Instead it will be fully electric and uses the signals from TDC- and TPS sensor coming from the ECU. Lots of benefits here!
5:07 though (regarding the revs that Diesels can't rev as high) I would humbly add that not only is the mass of all components in a Diesel higher which will clearly have a negative effect slowing down moving parts as a result of component inertia somewhat, but Diesel engines also operate on the principle of self-ignition, where the diesel fuel is ignited by the high compression of the air-fuel mixture in the cylinder without the need for a spark plug. This requires precise control of the injection timing and a relatively longer time for complete combustion, especially at higher speeds. As engine speed increases, the diesel has less time to fully ignite and burn. This leads to inefficiency at higher RPMs and can, or will, cause the engine to knock. By comparison, gasoline/petrol engines can precisely control the ignition timing through the spark plug, even at higher speeds, allowing them to operate more efficiently at higher RPMs and subsequently reach much higher RPMs.
Your videos are great. You explain mechanics so efficiently, including everything that is needed in the proper timing and complexity. Great stuff! Subscribed/Thumbs up!.
just an idea, but what if we just take a inline 6 cylinder engine, do combustion in every cylinder at low rpm / a setting in the car set to power, and at high rpm / a setting in the car set to efficient use 3 of these cylinders for the 5th stroke of the other 3 pistons? Anyone wanna try this idea with me? I really think this could work, the only thing is that you would compulsory need free valves to keep the (I'm gonna call it overflow-valves) closed and opened at the right times. What do you guys think of this idea, could it maybe be practical or are there any problems with it? please write feedback i wanna hear y'alls opinions
Liked, because the video was very instructive while easy to understand. What I missed was a discussion of efficiency in terms of expansion ration, "time to work" is a bit vague.
My first thought when I saw the cooler exhaust feature of the 5-stroke was: "Doesn't the exhaust *need* to be kind of hot?" And I wasn't wrong. We saw issues arise when gas heating appliances (water heaters, forced air systems) were made more efficient. Suddenly vent pipes needed to be stainless steel and have condensation capture/disposal systems because the flue temperatures were below dew point for the moist flue gasses.
I take one issue with the “caveat” about the engine size argument. Yes, adding the extra low pressure cylinder accounts for size purposes but only the two high pressure cylinders count for volumetric calculation purposes. The low pressure cylinder is in-line with the high pressure ones so it doesn’t do anything to affect the volume of air being cycled into or out of the engine as its purpose is completely passive. I’m seeing this as a kind of “reverse supercharger.” Where a traditional supercharger takes mechanical energy from the crank to pump additional air into the intake, this concept takes energy from the exhaust gasses and turns it into mechanical energy directly into the crank. If your only concern is extracting as much energy out of a unit of fuel as possible and you have few or no limitations on space, this kind of design can make a lot of sense, particularly when paired with other efficiency-increasing techniques like turbocharging.
Very interesting video. Many thanks for that! BTW: Having high- and low-pressure cylinders was very common on steam engines in the late 19th century. Even machines with three or four stages were invented and build.
Most modern engines use variable valve timing tricks to keep the intake valve open as the compression stroke begins. This stores gasoline fuel in the intake manifold. This allows the combustion stroke to be relatively larger than the compression stroke, extracting more energy. Then it exhausts, and the next intake stroke draws the fuel-air mix back in from the intake manifold, along with new air, plus additional fuel being injected. The consequence of this is the compression ratio is lower, thus the power output is lower; but it does draw more of the energy out of the fuel.
Fascinating, thanks for this! I’d never heard of this engine type before (and I used to be a mechanical engineer). I guess this engine type would only be practical for situations in which the engine was constantly performing near peak power output. Maybe for aircraft?
Haven't watched a D4A video in a long time, but as usual, a great presentation by the host (and he has improved himself greatly from some of his earlier videos) of a interesting subject. What I find most interesting is that the early pioneers of the ICE were aware of the inefficiency of the design and were already doing something about it. In their day of low RPM agricultural work primarily, it was a technological marvel and answer to the drawbacks of a period ICE, but in our high-tech, go-fast times, it has its limitations.
How about a two stroke engine? Inject pre-compressed air and fuel, then instantly burn (1), then exhaust (2). If you inject fewer air and fuel, you will get throttling for free and more expansion. you can even start the motor from a dead stand-still (provided a cylinder is in the right position). pre-compression could be done by the engine during breaking. it might even be possible to switch between 2 and 4 stroke with software-controlled valves. or some kind of hyper-vtec.
You could get some adjustment for varying load by varying the amount of air allowed in during the intake stroke. Then, use a diesel version of these engines in applications in which most of the operation is at constant speed and load. Oceangoing (and even Great Lakes cargo ships immediately come to mind -- these run at constant speed for days or even weeks at a time. The one extra complication is that you would need extra provisions in the valve gear to be able to run the engine in both directions, since most cargo ships have direct drive from the engine to the propeller, and so this is how they back up. But i you could improve their fuel efficiency from the current ~55% to ~65T, it would be worth the extra valve complexity. The long running time of ships would also mitigate the catalytic converter warmup time, although I haven't heard of ships even using catalytic converters in the first place (but it might be in the works, to meet future pollution regulations). Another option is to split up the catalytic converter and put in the tubes from the high pressure cylinders to the low pressure cylinders, although that might be TOO hot. Also note that if you put in a bypass to let the high pressure cylinders temporarily exhaust to atmosphere, you can make the compressed air starting sequence very easy -- just feed the compressed air into the low pressure cylinders, and you don't need to have as high a pressure to be able to start the engine; then once it gets up to speed, cut out the bypass and go to 5-stroke mode. Generators have also been mentioned as a potential application for this type of engine. But we need to be making electricity as much as possible from renewable energy sources, whereas you can't run electric trolley wire over the ocean, and batteries don't have enough capacity; sails, on the other hand, could serve for part of the journey, but you are still going to need an engine for long parts of many journeys. Still, it wouldn't hurt to have some of this type of engine on standby as emergency generators in case of a dropout in the renewable energy generation.
Compounding turbo doses the same thing, (Down flow Turbo that’s connected to the engine crank shaft) please make a video on a Down flow Turbo. Great video!
so basically the reason for fail of 5-stroke engine is the same as for split-cycle one... It has some great advantages in very narrow rev range, so it remains theoretical construct in real world of permanently changing load, rev, and any other parameter you might think Great, comprehensive video, as always
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6:18 that black spot made me rub the screen thinking it was a little bug XD
The guy who in fact patented the 4 stroke engine was Beau de Rochas. Nikolaus Otto was the one who executed the idea.
Goddamn you are smart. I have so much respect for your intelligence. I'd guess you have a ≥145 IQ. Bc I don't believe anyone else helped you create the conclusion you ultimately came to, & obviously, no one wrote this for you. Both of which are testaments to a very intelligent mind's ability to research & think clearly. Thank you vm for your contributions to my understanding of engineering & physics. Anyway, your writing reminds me of another channel whose writing I find so intelligent as to be elegant, example, describing why perpetual motion machines cannot work:
_Without a difference in thermal states from which to establish a flow of energy ..._
_...mechanical work cannot be extracted from the system._
Episode...: _Pulling Energy Out Of Thin Air_
YT Channel: _NEW MIND_
YT specifier: UK8Fw5Zjna0
I wonder what your thoughts are on turbo-compound engines since they work in different way but have the same goal as the 5 stroke.
Why not do a video about the SAAB engine that had variable compression. 1,6 liter, 250 HP and fuel consumption of 4 liters/100 km (58.8 miles/US gallon). It was bought by GM and buried, since it was too efficient, or was it some other reason? I know that they had (at least) one engine up an running at Ring Knutstorp in Sweden at some point.
Driving 4 Answers manages to make videos on engine topics I've never heard of with pretty regular frequency. That's so rare on RUclips and I love it.
Agreed, This gentleman rocks.
We driving 5 answers today
beat me to it :D
@@eTiMaGoA rival appears!
@@d4a Did you cover the Mazda 2 stroke engine that has valves yet?
Outstanding. 😂
About to comment, then this is top comment. i hope your pillow is also hot on the other side 🤣
Sounds like a generator operated at a constant load and RPM would be a better use for the modern 5-stroke engine than a passenger car.
why not passenger car? most hybrid vehicles have some form of transmission, for as long as generator is of same weight as that transmission system it will be a net benefit.
@@fulconandroadcone9488Constant load and rpm is the exact use case of a range extender engine in a plugin hybrid. This would be perfect for that use case if a manufacturer intended to make enough to justify a specific engine just for plugin hybrids.
Also single engine GA planes (but good luck with certifying that lol), where using 75% of max RPM is standard
@@Thinginator would be better than mazda trying to put rotaries in hybrids as range extenders😂
Exactly what I was going to say.
This video is spot-on : a really good explanation of the basics, but also some deeper knowledge that is needed to really understand why these "improvements" on the basi cycle never got anywhere. I love the final teaser comments around "what would Otto say about his invention today?" .....I think he would be crushingly proud of that contribution, and in the same way that Mozart would play synthesizers, Otto would really appreciate variable valve-timing, turbos, fully digital control systems etc. Well done!
It wasn't abandoned - I instantly recognized this as a double expansion engine and steam engines in ships were using even triple expansion engines for decades until they got replaced with diesels.
yah this shit has been talked about for decades. Wont go anywhere other than for tiny engines with no torque.... it doesnt work properly. Otherwise someone woudl have built one and produced it. When somthing goes prototype so many times and its just abandoned..... its usually either to soon without the tech or just flawed.
@maxkool1330 its not that it doesn't work, as it worked quite well in steam engines for many decades. The problem with adapting it to ICE applications is higher initial cost, added complexity, and size constraints. Fuel efficiency means nothing if the monetary savings plus some are eaten up in the additional costs to buy and maintain the engine. If you go to any wwii era museum ship and see the engine spaces, youll find a crazily complex mess of pipes and equipment that took dozens of sailors per shift to keep running; the engine room of a moden diesel engine ship has an engine room thats fairly simple and open and requires less than 5 sailors per ship to operate. At the end of the day, the option picked the vast majority of times is going to be the one that leaves the most money in the bank at the end of the day.
Steam engines! Should be done for Diesel-Engines.
Some Railway 'Compound' steam engines too.
I would believe it might work for running a generator or other more single speed use. However the additional complexity makes other options better.
10:53 “twice the balls, half the hair” 😂😂
In my case is twice the hair and half the balls due to testicular cancer😅😂😅
@@littlejefe494😂, but😢
😮😮😮😮@@littlejefe494
@@littlejefe494sucks man, hope your doing fine
@@littlejefe494 Sucks to hear, you know that reminded of the fact we all got microplastics in our balls nowadays, and in our dicks too according to a recent study. related?
Just call it what it is, a compound engine. Steam cars, tractors and locomotives used it the most.
That's what Verbund Motor literally means. 🙂
exactly. its a 180 year old tech used in 150 years old design, yet it took 150 years for "someone" to do it?
retarded!!!!
Current ICE designs are still using the first design principles of not using exhaust gasses or optimizing mechancal loads making us waste around 70% of fuel.
Exactly! Some books say Gottlieb was inspired by compound steam engines he saw in the UK.
You beat me to it! And since ships and trains generally operate at a constant load and speed, the engine can be optimized for those without the offspeed drawbacks mentioned here.
@@brianmack6285 exactly, might make a comeback as range extenders someday since they also are operating at constant load and speed.
For me an extremely interesting and very well presented video. My father was an aero engineer with RR and DeHavilland, back in war WW1 he was among the first to join the Royal Flying Corps. As a youngster he taught me much about 2 and 4 stroke engines but alas as my feisty years approached ‘life’ took a greater part and so much of what he knew was last. But whenever I would tell him about new advances, at least new to me, he would reply it’s all been tried before !! And he would tell me who where and why it failed, or was successful in some cases. I am eternally indebted to him for his efforts, but I think we may have missed the 5 stroke, but I’ll also bet he knew of the process. Thanks again I will forward to my son, take care
External combustion engines are far less efficient 0:04
They do blow up efficiently and use all the energy to destroy the car
They're more efficient in a way
On the contrary, it depends on what they are trying to do. a bomb is very efficient with its energy usually :)
I think Stirling engines get slightly better efficiency, of course at the cost of power, among other things.
@@ULouOW well, if you count the energy to unalive a person, as it is its inteded use, its very uneficient, as I remember in a war you need about 200kg per person of explosives
Hello from finland.
I am mechanical engineer, and I most love your clear explanations and great videos.
Most of things are clear for me, but you still can educate me. I am more than happy to learn from you.
For example the EGR: I never thought about “dirtyness” in intake manifold caused by piston rings! As you explained it, it was completely clear. Of course
Your videos are most relaxing and professional and clear as far as I know.
Excellent work!
Engines were NEVER designed to have recirculation exhaust back in the intake thats why old engines last longer than new ones for example old diesel engines last up 1M miles vs DEF engines that may go bad at 30-50K miles same goes for the CATs in the exhaust they get plugged up like an old man with no fiber in its diet 😂
Let us not confuse EGR(Exhaust Gas Recirculation as an emission solution targeting nitrogen oxide), and PCV(Positive Crankcase Ventilation as a solution for combustion products that make their way past the rings, contaminating the engine oil).
Clear explanation maybe, shame he doesn’t know what he’s talking about.
What the Finn said above. I have subscribed.
17:50 Letting you know... steam turbine technology is just a few years behind ICEs having been invented in 1884. Electric motors were invented in 1832, so they are 192 years old. ;)
I was looking for this comment :-)
@@tifogra689 I feel bad, but he did ask.
Yes but his main point was how ubiquitous ICE engines have been in life for so long. Steam engines came and went. And the electric motor, while invented in 1832, did not become incredibly common until recently.
@@magmatri-studios If buy recent, you mean only the past 80 years, you would be correct.
@@magmatri-studios steam is to this day wildly used for power production
When I was in college in 2014, a group of 3 of us did a feasibility sudy on this concept. We determined that there was no design goal for which a 6-stroke engine was the optimum solution (terminology we used, but it was the same thing). If power density was desired, a bigger conventional engine is the best choice. If efficiency is desired, a turbocharger or turbine generator (for a hybrid system) on a smaller engine is best.
It's a very interesting concept and has the potential to do what proponents claim. But it's just not better than alternatives.
Everything is a compromise and it all comes down to money.
I think it would be good for generators or hybrids were it could be run at full power or not at all. Did you look at this?
What about a diesel version? Detroit now makes a road truck engine with a secondary turbine that harvests a little extra torque.
As a fellow engineer, I'd love to hear your thoughts. (Unfortunately, I got the wrong degree)
Really I think a turbocompound setup is a more viable solution. Takes a lot less space and you can simply disconnect the turbine from the crankshaft at low rpm.
Turbocompound system is also something that theoretically you can simply add to an existing engine design, almost like installing a supercharger.
@@danieltanuwijaya7675 This is the first time I've heard the term 'turbocompound', but yes, that is what I was describing. I just had to look it up.
Turbo is good for power with fuel efficiency, but the air efficiency is poor. Turbos burn a lot of air and make around twice the Nox and CO2
@earlyrobotmind All properly running, road going, gasoline engines burn 22% of the air they intake (the portion that is oxygen). Turbo engines avoid NOx by using intercoolers and lower compression. And the efficiency of turbochargers is often misrepresented.
5:07 Diesel engines don't rev as high because of the flame propagation speed in the cylinder, not because of heavier internals. Top fuel dragster engines rev plenty high, yet they too have heavy internals to cope with the boost pressures.
Right, but dragsters require crazy fuel mixes to achieve those revs. A standard diesel engine will be limited by the weight of the components it's being expected to shift.
Rather massive difference between top fueler stroke length (~4.5 inch) and a diesel engine stroke length (4.88 inch). Or in comparing bore to stroke diesel engines are undersquare while a top fuel dragster engine is oversquare. Longer stroke = more reciprocating component inertia due to higher velocities. If your crank radius is the same then a longer stroke piston has to travel a greater distance in the same amount of time at the same rpm as a shorter stroke engine. And you cannot just increase crank radius due to both the room it would take, lateral forces it would apply to the piston, and you'd have reduced mechanical leverage on the crank. When you get to the really big 'diesels' such as marine engines they use crossheads so the long component of the connecting rod can travel vertically up and down and retain a efficient crank radius.
Also remember: (way back when) Gas pump attendees used to smoke like chimneys while putting gas in your car. However, everyone stopped smoking when the top fuel drag cars were in the shop. Why? Few outsiders know this. Nitromethane - that yummy ingredient in dragster fuel - is a liquid high explosive. It's mixed with methanol in just the right amount to be sent through a fuel system. In some ultra-high-speed videos of dragsters doing dragster things st the Christmas tree, you can sometimes see liquid coming out of their exhaust pipes. It's because the fuel is a high explosive that dragster engines are so heavy. NM... nasty stuff, also glow plug airplane fuel!
No, the internal components of an 11,000 hp top fuel engine are lighter than what's inside my generation one small block 400. The difference is that these parts are made from extremely resilient materials: tungsten, magnesium, and exotic aluminum alloys, which provide strength, and extremely light weight.
That was a wonderful argument and technically correct. Unfortunately these engines are not built based on how fast we want the flame front to propagate. The reason a diesel engine turns slowly is they want it to last a long time there's a lot of other things but longevity can be counted in revolutions or years and if you're turning a lot of revolutions in a minute like a drag racer you have a pretty fractional part of a year that you actually run. That big heavy slow torque engine turning slow, forever is a strong selling point on the industrial market. The drag racer Markets very well to young people who are buying something to last a day.
I had a bad dream about a 5 stroke engine and woke up exhausted.
Good presentation! For automotive engines, the advent of variable valve timing is another thing that makes this concept obsolete. You can emulate the Atkinson cycle when running low revs at part load (and get some "internal EGR" for a NOx emissions benefit) by delaying all of the valve timing events. When the driver wants power, you can shift the valve timing to what's best for power output, and you're not stuck with a fixed set of events or a fixed overexpansion ratio like this concept is. And you can fiddle with the valve timing (among other things) during cold-start warm-up to help the catalyst light up.
Bro my Captions said Sad vacuum cleaner noises when he revved the car.
ps3 era gran turismo games be like.
Mine said "*sad vacuum cleaner noises" 😂 I'm dead ,💀
@@alrecks619 🤣🤣🤣🤣🤣👌
@@Rpzz0 🤣🤣🤣👌👍
0:40
The Porsche approach of just using a turbine to turn the energy in the exhaust gas into electricity seems better. That approach naturally deals with the fluctuations and turbines are a well developed low weight way to harness energy.
Exactly! Same concept, clever solution.
still, under light load, the consumption wasnt better. and most of the time, the engine in a car is under light load.
But.. wind turbines cause cancer....
This type of engine (turbo compound) was used on large bomber aircraft in WW2. 😮
@@BlacKi-nd4uy The key difference with Porsche's approach (not really theirs as it was obvious but they got it out) is that you *aren't* using the recovered energy to send to the output now but saving it in a battery for later use -- including for running a turbo.
That solves the problems about light load -- during that time you let the engine do all the work and store the recovered energy. When you need a bunch of power you have boost w/o lag (the 'turbo' is really an electric motor running ogg battery) *and* you can take that battery power and directly drive electric motor in transmission.
--
Those planes used a mechanical linkage w/ crankshaft which meant that if you had enough torque at the rpm already you weren't going to get much benefit especially w a carb and no ECU (no way to cut fuel at a given rpm and let turbo make up during light load).
Also there are issues w/ losses involved in needing to sync turbine and crankshaft speed. Electric motors can go after the gearbox and every part can spin at it's optimum rate.
Isn't another reason why the 5 stroke engine did not take off is that fuel injection has allowed 4 stroke engines to effectively reduce the intake/compression stroke by leaving the intake valves open beyond BDC and delaying fuel injection until later in the compression stroke?
Get atkinsoned
As I heard it, the intake valves are left open after BDC because some inlet gas is still moving inwards at BDC - which means that you can increase the inlet charge basically for free. Just after BDC the inlet valves are closed; which creates a shock wave that improves the mechanics of compression. p.s. they did this on carb engines as well.
Yup. That's called "modified Atkinson" or "simulated Atkinson" and it achieves similar results without the fragility of the extra linkages in the genuine Atkinson design. The Toyota Prius and some other hybrids use this valve timing cycle; it was never really viable for cars until hybrids because the torque output is pretty poor, especially at low speeds. The EV system in a hybrid supplies good torque even at rest so the engine's shortcomings are covered.
@@leifhietala8074 Or "Miller" if it has a turbocharger.
That's called a Miller cycle engine. Does require a supercharger though.
This is one of the best-organized, best-written, and best-narrated technical videos I've ever watched. Very enjoyable. You have a new subscriber. Thank you.
Funny thing about Otto and Daimler's Verbund Motor, we see the exact same principle used in Mallet (pronounced Mal-lay, not mallet like a hammer) type locomotives. Of course, a steam engine is an external combustion engine, but your working fluid is essentially doing the same thing, expanding to push a piston and produce mechanical work.
A common gripe for railroads back in the day was that range was limited by both water and fuel. You can build more water towers along a route to supply more water for your engines, and you need to. Water is safety critical. Without enough water in your boiler, it can explode as the crown sheet of the firebox gets too hot and warps under the pressure. Water is cheap, hook the tower up to a well and pump groundwater in. So long as you have the water rights, you're golden.
So thats water solved, how about fuel then? Well, in the early days engines ran on wood here in the US. Wood was everywhere, it was plentiful, and cheap as dirt. Wood isn't very energy dense though, and as engines got bigger and more powerful, they needed more energy dense fuel. More energy density in your fuel means more energy in a firebox of the same volume. This improved things on American rails significantly. Unlike Europe though, the US had and still has long, desolate stretches that can go on for hundreds of miles, so time between fuel stops was a big limiting factor. Furthermore, fuel is expensive.
Swiss engineer Anatole Mallet realized that steam was only being allowed to partially expand in the cylinders, and after that, was simply blown out the stack to draw a draft for the fire, keeping it hot. Why waste that energy? He designed a new type of locomitive. They had huge boilers, and massive frames. They were so big, they had to have the frame hinge in the middle so it could bend around corner while the boiler hung over the side. They also had two sets of cylinders, making them compound engines. The first set of cylinders used the high pressure steam, and were towards the rear of the engine. They exhausted to pipes which carried the expanded steam to the low pressure cylinders, which were much larger to account for the already expanded steam and resided at the front of the engine. After being expanded again, the steam was allowed to vent through the stack, pulling a draft just like before.
These compound engines saw somewhat limited success, but by the 1920's, were viewed as obsolete by the industry at large, as moving more tonnage at high speed became more important than saving a little on fuel. They did their jobs well, and are an important, if underappreciated part of railroad history. The last surviving American Mallet is Norfolk & Western 2156, and she resides at the National Museum of Transportation in St. Louis, Missouri.
Three key points:
1. The moment you mentioned part-throttle operation, the penny dropped. The science is sobering.
2. The main reason IC engines rules is the energy density of the fuel it uses. It doesn’t matter if you lose 65% when you have a gazillion percent to start with. Looking at you, lithium ion bleh…
3. My best conclusion is that the future lies in hybrid technology. Instead of IC versus Electric, combined these two can make a formidable team.
Except that the other key point you seemed to have missed: do not understimate the importance of simplicity, and the problems with complexity.
An EV drive train with li-ion IS the new 4 stroke engine platform. Using the principles of 'the cumulative production of a technology platform and exponentially decreased costs' - i.e. why the 4 stroke engine has been the undisputed winner, means it takes another propulsion platform that is architecturally superior in thermodynamics (check), with a set of sub components that each enjoy benefits of manufactured scale (check).
Add in the simplicity, and at that point it only becomes a matter of time that a low enough price and scale results in the displacement of the 4-stroke ICE engine. No doubt, it has had a great run and made a great contribution to humanity. But we also need to accept it, and say good riddance.
Again, reality is far from naive theories. Hybrid cars combine the worst aspects of both worlds and are utterly senseless in practice. With an engine drive train combination which ist 10 fold more efficient compared to ICE technology from the 19th century fuel energy density becomes much less of an issue that you would like to think. Most people are stuck 20 years in the past in their knowledge of EV and this is like 100 years in ICE time.
@@itschrisuphere The complexity of an EV lies in it's battery, ignoring that and focusing on the motors as if they are the only component that matters is ignorant at best and intentionally misleading at worst.
An EV, though it may have less moving parts, is not simpler than an engine, even modern ones with all their sensors and emission controls.
@@rock7343except that complexity manufacture is different from part complexity. And having a magnitude fewer moving parts is not something you can ‘hand wave’ away (again, see equivalent analogues for other non 4 and 2 stroke engine types re: this video)
@@itschrisuphere The problem is that lithium battery costs are stagnating and still not at a point where they cover all use cases (low range, slow charging, etc.). EVs currently are more expensive then compareable ICE cars and that wont change unless battery costs go down alot more.
In aviation, we had the turbo-compound designs made in order to harness the remaining energy of the exhaust gases. This also led to very complex and unreliable engines although they actually brought better efficiency. All these have been wiped out by jet engines which are less efficient but far more reliable. And reliability in aviation is by far the key factor.
You mean the r3350 with the power recovery turbines? Like you say i think it made sense that they went out in aeroplanes with the introduction of jet engines and their very superior reliability. But i'd never actually thought about using them in cars before, i wonder if it could be worth a shot seeing as they've stayed with piston engines. Wikipedia's r3350 write up says they managed 20% recovery, but mechanics called them "parts recovery turbines" because of increased exhaust temperature causing dropped valves. But it does sound like this improved with time. I wonder if they could be made to work on a car.
@joecook3223 Yes exactly. I meant the R3350 in its turbo compound version powering the DC7 and the Super Constellations. The Connies were often finishing their flights on 3 engines sometimes 2 !!!. I don't know any implementation of the turbo compound tech on a car engine, but I heard Volvo is using it on some truck engines. Here again, reliability seems to be main problem preventing this solution to be widely adopted.
Or MGU-H in F1 engines.
A turbo compound in a diesel passenger vehicle would be very interesting and probably quite efficient.
@@joecook3223 Turbocompound engines in the modern form are the F1 power units but instead of directly transforming the waste energy as work the MGU-H recovers that as stored electrical energy. Compound engines make the most sense for applications with a constant load and rpm, as is the case for planes.
In reality these won't work on regular cars because in daily driving there is not enough exhaust energy to be recovered to warrant the extra weight, complexity, and cost. In fact, I think we are approaching the limit of extracting more thermal efficiency from ICEs because the biggest concern these days is getting the catalytic converter up to temperature and emissions regulations are increasingly targeting cold starts (where most of emissions come from in modern cars).
Damn, this guy gives so much hope at the beginning of his video and then tore it down with such ruthlessness at the end that I lost hope on future ICE engines.
ICE will outlive you.
🤣😂
You shouldnt. Funny comment though. Lol
No! He is telling you it took us 150 years to take Otto design this far and every next tweek will be more and more difficult and will take time, eh?
Regardless, he is very informative.
Hello, I am German and I have not understood every word but I think I understood the main problems.
Thank you very much for these informations.
My first idea was the the problem with too low exhaust temperatures so the catalyst can not work without added electrical heating.
The main problem is the partial load range. Even on big roads a normal car with 150 hourse power only needs 20 to keep a speed of 60 MpH.
It looks like a supercharged version of this would work well with boats or airplanes, where high rpm cruise is the norm. It will not work with automotive, or motorcycles, which spend a lot of time at no load and low rpm.
Finally, at 2:15, you explained WHY the turbochargers don't take power from engine and use instead "energy that would be wasted otherwise". Until now I didn't get how the presence of a turbocharger wasn't having a bad effect on the rotation of the crankshaft. I was thinking that it was the piston to push out the exhaust gas and therefore anything that wasn't a completely free exhaust pipe I thought was having a bad effect, "slowing" the motion of the crankshaft.
Turbos primarily operate off the difference between temperatures from one side of the impeller to the other.
@@Longbowgun like a carnot engine? i mean very different but still
@@Longbowgun Huh? The impeller is spun by flow across it, not by temp difference. Hence a larger downpipe with less restriction can allow for better turbo efficiency. Air temp only matters with cylinder charge. Cooler air means more oxygen which increases the cylinder charge. Like a windmill, higher air speed across the blades the faster it spins. Flow through the impeller is exhaust gas, not intake air. Or im not understanding what your trying to say?
@@jeffco908 You are correct. It's the flow that causes the impeller to spin. At the same time, if you could somehow encase the turbo so that there is zero heat loss, when you measure the temp before and after, there will be a significant drop in temp. Same goes for pressure. These two drops are equal to the energy transferred to the intake side of the impeller.
This is an example of the 1st law of thermodynamics. Energy can't be created or destroyed, only transferred from one form to another. In this case, the pressure and temp of the exhaust gas is transferred into the torque of the impeller. The 1st law doesn't stop there. That torque is then transferred into increasing the pressure and temp of the intake air.
Toyota recently said that it teams up with Mazda and Subaru to develop some more ICE engines. I think, Volkswagen said something similar recently too. ICE engine will stay with us for the nearest future, that is for sure.
I would say 50 years at least. Now that companies are making mass market EVs the world sees that they are nonsense and all the hype was just hype. Hydrogen is promising but is still a long ways off. It will take a decade or more to develop a commercially viable hydrogen powertrain and decades more to build up infrastructure. ICE on the other hand is here, well known and tested. We can develop alternative fuels much easier that building hydrogen infrastructure. So considering all of this I would say ICE is here for at least the next 50 years.
But increasingly relegated to niches: high performance, cheap retrofits, novelty, etc. Once a transition (like electrification) gets moving there’s little reason to invest much in the old. I think Toyota believes everyone jumped off a bit early so there’s room for some ICE development still, but I suspect very little. I’ve studied these tech substitution models in several industries and so the math is convincing me. But I get things wrong like anyone.
The main area I think ice will continue to be relevant is as a range adder or hybrid component in haul and remote location use work vehicles
@@myonen4402 And seasonal work like farming - from harvest to seeding. Spraying and fertilizer spreading could be done without ICE and massive improvement in battery energy density.
@@valtersvasilis yes I also see that an EV with a compact diesel electric generator could constant charge the batteries @ peak thermal efficiency would actually be amazing for me as an electrician because I could literally use my truck as a job site generator
I saw an old steam-powered barge boat on either the Mississippi or Missouri. It used 3 pistons, small where the high-pressure steam went in first, then to a medium and large piston, extracting all the useful work from the steam. I remembered that from 30 years ago when seeing your animation with the low-pressure pistons.
Useful because it didn’t need to stop and go. Continuous high torque.
Great video. I really liked your graphic on torque contribution for each stroke. I also liked you explanation of how higher compression ratio increases power. Thanks.
i cannot express how much i appreciate these in depth videos, you are very knowledgeable
This seem like an ideal engine for an electrical vehicle range extender. As an engine used to charge the batteries you can run it exactly at the optimal rpm and avoid the problems of diminished (or negative) returns at low rpm.
I had the same thought. Not sure if that's great minds thinking alike, or two idiots having the same idea...
Also, how much extra energy could be extracted by boiling water with the heat left in the exhaust gas after it leaves the catalytic converter?
The Atkinson/Miller cycle engines already do the same thing without needing a custom engine block. You can just take a regular Otto engine and change the valve timing and connecting rods.
Uhm... yeah... you are 30 years behind the curve here, guys... you're talking about "hybrids"... except you are getting ALL of the emissions at a 5%- 7% efficiency as you are not actually transferring any combustion energy to the tires... which is why we had the hybrids in the first place; the engine running uses the same amount of fuel whether or not the power hits the road...
@@frontiervirtcharter well, as the exhaust temp would have the be WELL above 212F/ 100C to boil water and you can put your hand in the exhaust flow without getting severe burns... and you can actually SEE water DRIPPING out of tail pipes... I'd say NONE.
What you described are known as multiple expansion engines in naval engineering, and were obsolete 70 years ago. Between the world wars naval warships migrated from the then-common triple expansion engine (you describe double expansion engine) to a better method of harnessing power - steam turbines.
During WW2 however as the US ramped up its lend-lease program to expand supplies to Allied forces in Europe (and then even more so once it officially joined the war) this style of engine saw a dramatic resurgence in popularity as its simpler, faster, and cheaper to produce than any of the competing turbine models of its era - keeping in mind that all naval power plants operated by steam power, using some mix of coal (really old ships) or bunker fuel (heavy fuel oil that has to be heated before it can even be pumped) to boil sea water to generate steam which then allowed power via expansion to be leveraged however it was needed.
Triple expansion engines work great in naval applications as they can be sized to the application, and the overall scale is so large that entire banks can be brought online or held in standby rather than throttling up or down an individual plant, allowing a ship to simply bypass the performance deadzones that exist as you outlines.
you, um.... are aware that steam turbines are simply multi expansion engines, right? other than single stage delavals, theyre all compounded to a certain degree...
@@paradiselost9946 Since I know the applied naval history I took it as assumed that I understood the operating principle :)
Though you’re right, many won’t have that context - that all of these discussions are about century+ old technologies. History may not repeat itself, but it does rhyme :)
Seems the better approach to do this multi stage expansion engine is sticking a turbine connected to the engine's exhaust manifold sending extra power to the crankshaft. A whole lot more compact. I believe some old WW2 planes and some truck engines do this.
@@danieltanuwijaya7675 or an electric motor, like the F1 MGU-H
@@danieltanuwijaya7675 yes, that technique of essentially using the front stage of a turbocharger mechanically coupled to the crank was also used immediately post-war (not sure it actually made it into combat), though with the rise in jet turbines the days of that technology were extremely limited.
The term you’re thinking of is “turbo-compounding” - distinctly not the same as a compound super-turbo-charger (keep in mind that in that era “super” charging meant “mechanically engine driven” while “turbo” meant “driven by a turbine, essentially always in the exhaust”). This works essentially by replacing the compressor end of a turbocharger with direct link to the crank, so that exhaust gases drive the crank rather than increase engine power. I don’t watch Formula 1 but I suspect their mechanical energy recovery unit (or whatever it’s called) works under similar principles.
Extra credit for "usurpation" - excellent video as always.
They could have made it even more efficient if they made it as a boxer engin to eliminate the counter weights.
As an ageing thinker of a more philosophical bent but who couldn't engineer his way out of a paper bag in a life-threatening emergency may I congratulate the maker of this video. Matters ere explained with a straightforwardness and clarity that I find rare. I have subscribed and look forward to seeing more. If engines can be explained to me somebody is achieving something.
Beautifully done as always.
When a teacher knows his (or her) stuff and uses language precisely and concisely, you're in for a good lesson.
I come to this channel for the wrinkles in my brain, but I stay for the delicious diatribes you close the videos out with. 😂 "Don't tell me ICE is dead : Read the room!"
I commented on that too. The jab at the end was awesome. Great content over all.
It's actually the EV that is on the deathbed. Tesla has over 67,000 unsold EVs hidden in carparks all over the US, VW is redirecting €60 *BILLION* from EV development back to internal combustion engines, Fiat is retrofitting the 500e with petrol engines because the battery vehicles aren't selling, both GM and Ford are 'scaling back' (read 'stopping') production of their EV Silveraro/F150 Lightning due to 'lack of sales'....
All this in an environment where the commodity prices of the raw materials required to build lithium ion batteries (lithium, cobalt, copper, nickel, manganese, etc) have fallen off a cliff!
If it wasn't for 'carbon credits' (please don't get me started on those!), Tesla (the company) would never have gotten off the ground.
I now know how to save ICE cars from the impending EV apocalypse! It’s simple, we return to steam… Add a boiler and turbine to an ICE car’s exhaust system that captures the waste heat and converts it to power. Boom, 100% efficiency achieved! You can mail me my engineering award at your convenience, no rush.
@@davemccage7918Steam engines have even lower thermal efficiencies of ICE engines and ICE engines seldom achieve 35 percent efficiency in real world conditions. Take it for what it is: ICE was an improvement over steam and EV is an improvement over ICE… Don’t believe me? Ask yourself why farms retired their old flywheel powered tools and appliances that were connected to loud and smoky hit and miss engines around the turn of the last century when electricity was brought to rural villages…
@@davemccage7918 EV's do use steam power, if you account for how the electricity is generated before it gets to the charging station 😉
Serious thought here - if ILMOR's 5 stroke design only extract the expansion cylinder's benefit at high loads, why not apply the engine to use cases that are near constant high load? Imagine a horizontally opposed version in light aircraft. Four HP cylinders and 2 LP cylinders would fit perfectly in the space for existing boxer 6 designs. Aircraft operate in a narrower RPM band and at higher load than automotive applications. The external turbocharger could be better sized to benefit from ram air and lower exhaust pressure at altitude.
A 5 stroke design also mimicks the pinnacle of large piston driven aircraft radials of the 1950s that used turbo-compounding to extract exhaust energy. The Wright R3350 was used in the fastest prop airliners like the Douglas DC-7 and Lockheed Constellation and had exhaust turbines that drove a shaft coupled to the engine crankshaft (instead of an intake compressor wheel).
Turbo compound engines were effectively replaced with gas turbines.
@@Appletank8 Right, turboprops are higher performance and lower maintenance for commercial and military applications that need higher thrust and/or longer range - cargo planes, small commuters, helicopters, etc. But who is spending half a million dollars to put a Pratt & Whitney PT6 in their Cessna?
It could be a good design for a standby generator, except the complexity would be cause for more maintenance, negating the potential benefit.
The real answer to this is good luck getting a design approved by the FAA within the next 2 decades for less than $10 million dollars.
@@iamaerix True. As an outsider that just follows aviation out of curiousity, it's amazing that General Aviation seems fine with 70 year old engine technology. The FAA finally just approved unleaded avgas for christ's sake. It's like Lycoming and Continental have a regulatory moat around their business.
My 2021 Ducati XDiavel has 13-1 cr, 4 cams, Desmo valve control of 4 per cylinder and 160hp.
The bike is very fast and gets fantastic gas mileage... I'd call that efficiency. Great video by the way!
And motorcycles are notorious for generating more NOx than a car. High revving, high compression.
Er, it's a bike.
@@greenaum You're brilliant eh?
Ironically in 2003 I was working on a nearly identical engine. I called it the double expansion engine. it worked similar and I agree with most of what you mentioned. The same result can be made from a conventional 4 cylinder in line, where the two middle pistons act as the double expansion part, that would allow for using nearly all stock components. Regarding the low speed vs high speed, this engine would be best suited for hybrid vehicles, with the engine tuned to run only at optimum RPM to charge the battery and/or cruise at hiway speeds.
Thanks for your very informative and entertaining videos. I'm so glad I found your channel about a year ago. Learned so much since then.
And you are absolutely right, the era of the 4-stroke combustion engine is far from over. We might get new fuels, or it might be used to power the generator for electrical drive. But I think battery-EVs are the entirely wrong way.
"Let me know when any kind of propulsion technology manages to last 150 years" - well... sail propulsion has lasted thousands of years and is still in use and getting improved. Horse drawn stuff has also been used for thousands of years and and is so stuck in our culture that we still compare our engines to horses by using horsepower as unit.
missed the complexity qualifier
Ah yes, man's greatest engineering marvel: Horse
he never said those words
That's funny because electric propulsion predates ICE and will most likely also survive ICE.
Once we've solved the battery issues ...
"And let me know when ANY kind of propulsion technology manages to last 150 years, thank you very much." That is an easy one. The bicycle!
Just here to let you know - electric motors have existed for longer. Michael Faraday demonstrated circular electrically induced motion in 1821, Sturgeon demonstrated the first practical DC motor in 1832 and by 1838, Moritz von Jacobi built an electric boat that carried 14 people across the Neva river.
Fair, but electric motors is nowhere near as complex as an Otto cycle engine and hadn't been used to power a car until very recently.
@@danieltanuwijaya7675that's actually incorrect. The first electric car was built in the 1880's, but the first electric vehicle prototypes were built as far back as the 1830's.
@@danieltanuwijaya7675you don’t know how a permanent magnet synchronous machine (aka electric motor used by teslas)works, it is more complex than combustion engines, in my opinion
Yes however obviously a prerequisite is the use of the worst cluster devices known to engineers, batteries.
@@lucasv5359 I'm familiar with electric motors and no they are nowhere near as complex as the average car engine (it's magnets on a shaft on a housing filled with copper coils), at least mechanically. They (PMSM motors) do need some fancy inverters and controllers to work but so does a modern engine these days with their ECUs.
I remember reading about this years ago when those articles you mentioned started going around, and I ended up coming to the same conclusions about low-load performance that you did. Efficiency wise, modern Atkinson cycle engines achieve roughly the same goals while allowing companies to use existing engine block designs, just increasing gross compression/expansion while redesigning the intake cam profile to hold the valve open during the first 1/4 of the upstroke to reduce net compression. Much easier and cheaper that way.
I do think this type of design does have a couple advantages in terms of reduced parts count versus the standard four stroke engines of comparable size and cylinder count. The engine as built only has two fuel injectors, two spark plugs, and associated wiring/plumbing, versus three or four. The intake manifold only goes to two intake ports, and the exhaust is just a single pipe with no actual manifold needed. One thing the 5 stroke engine can do that I don't think Atkinson cycle engines can is run off of a carburetor; since carbs run entirely off of relative vacuum in the intake manifold, and Atkinson cycle engines push part of the intake charge back into the manifold, I'm led to think that the pressure pulse traveling back up the manifold would interfere with the operation of the carb, and thus the engine itself. I suppose where I'm going with this is that the niche for 5 stroke engines might be for moderately small generators - those all use carbs, tend to run at higher sustained loads, and would absolutely benefit from improved efficiency and the lower exhaust noise. Who's willing to invest the money, though?
Jay Leno talks about technology, how it need to be better on all fronts. It cant be better in some, and worse in others. It has to meet or exceed all expectations, or it just has no hope of catching on.
One Idea I just had for this is to maybe make and inverse 2 stroke design. Most engines want to keep exhaust byproducts out of their crankcase. However, if you could channel the escaping exhaust gasses to help drive the piston up on the compression stroke, and have it escape naturally out the crankcase, you could achieve a similar effect to a 5 stroke design.
A few problems I see with this though all pertain to oil. The first being, how do you keep oil in the motor. If you vent it into the crankcase, its going to blow the oil out through the exhaust. Next would be oil life. You are going to introduce exhaust byproducts into the oil, reducing its lubricity. You will also heat up the oil leading to further oil degradation.
Alas, I think the problem lies outside the engine entirely. In the titanic, the triple expansion engines would utilize the steam to its entirety... or not. After leaving the triple expansion engines, the steam would continue to go through a turbine. Turbines have several advantages and disadvantages, one being that they are not ideal for fast acceleration. However, if you could mount your turbo charger to the front of the engine, and have it couple to the engine via the serpentine belt, you can gain a lot of advantages.
By having the turbo essentially coupled to the crank, you can have something that can add power to the engine. As its going down the road, it can add rotational energy through the belt and assist the engine by using expended exhaust gasses. By doing so, you also relieve the engine of the load that is typically transcended by the serpentine belt. I love watching Engine Masters on Motor Trend, no Discovery. One on episode, they wanted to see just how much power you were losing to your accessories. They saw 40 horsepower depart the system just by driving an alternator, a water pump, and a radiator fan. Now add in all the extra crap that manufacturers have bolted on, such as Air Conditioning, Power Steering and the added load of the Alternator, and you can probably see losses nearing 100 horsepower in some applications. I say nearing, and every situation is different.
That turbo charger belt can effectively remove that load and add power to the engine in the same stroke.
Not sure why you think you can get 100HP out of a turbo or why you wouldn't gear it directly to the crank. The accessory drive on a car engine is not a very efficient way of transmitting power or torque. it is literally designed to slip so that a seized alternator doesn't take out the whole engine.
What you are referring to is a turbo compound engine and it has already been done in aviation. It was a stopgap measure that wasn't used for long because turbine engines were superior in every way. It would be a great way to make a cost-prohibitive car engine that would be unreliable. The Wright 3350 used in the B-29 spent far more time in the shop than they did in the air.
@Lurch-Bot so, what I'm talking about is not a force induction engine. it would continue to be naturally aspirated. you could make it turbo charged, but I don't think that would be ideal.
my idea of using the serpentine belt is strictly for maintenance purposes. I don't like the idea of having a solid coupling to the crank. having the serpentine belt would make maintenance easy, as you could have a new belt installed relatively easily as compared to something like a chain or gear drive.
as far as the 100 horsepower, I don't know what realistic expectation I could have for power output from a turbine off the exhaust. it would obviously be displacement dependent as a 350 v8 would probably give more exhaust resources than a 3800 v6.
I don't know to what exent you could get, but for kicks and giggles, let's say on my classic truck, I flip the manifolds over and mount a turbo in line with the serpentine belt and have twin turbines driving the serpentine belt connected to my crank. my engine currently makes about 300 horsepower. I believe, while maintaining naturally aspirated, I could make it have 350-400 horsepower. i would probably upgrade the belt from a 6 spline to an 8 spline, but that's relatively inexpensive
- ...Was ist los?
- Herr Otto, we revived you for a few hours so that you may see the impact that you made on the world.
- WAS!?
XD
I'd like to imagine him (like a few others) being like "Wait, you still haven't come up with a better idea yet after that long? What are you waiting for?"
"It's been 150 years and y'all still used it?"
Or: Here is my new improved engine that now can be made 😮
150 Jahre später, Technologie zur Wiederbelebung der Toten, und du spielst immer noch mit meiner Scheiße? Idioten.
“..read-the-room!” What perfect delivery of that old chestnut. 👏🏽
“Let me know when any other type of propulsion system last over 150 years!”
(Firearms has entered the chat)
@@davemccage7918 But only as a shaftless horizontal engine.🤣🤣🤣
@@davemccage7918 The fact firearms make your list of propulsion systems is telling.
@@artysanmobile I mean electric propulsion predates petrol engines and has never stopped being used in one way or another either. Just not in personal cars primarily.
@@tonymorris4335 Toyota is the current boss in hybrid technology, which I believe will be necessary forever. What they are doing with gear-sets replacing a belt is absolute genius.
Generally speaking, the surer path to heat efficiency is bigger cylinders, fewer of them, and slower speeds. In the late 50s/early 60s Deere were building a huge 2-cylinder engine for its larger tractors that set efficiency records that wouldn't be broken for 16 years. So instead of building buzzy little 4s, maybe we should be focusing more effort on 3s and even 2-cylinder engines for powering the ICE side of PHEVS. Soft motor mounts absorb the worse vibes of low cylinder counts and the hybrid system takes care of everything else.
My father has one of those that was converted to run on propane and I can count on my hands the number of times I remember him "filling it up"
Propane has a lower heat content than diesel. Its very popular here in Europe because it's so cheap, and its sold at peteol station.
Just bought a RE Himalayan. Love the single
Exactly. There are practical limits to cylinder size depending on application but for gasoline road passenger vehicles the optimum is somewhere in the 600cc to 800cc range. The ONLY reason you see so many vehicles with 2.0L inline 4's is due to various government laws. The USA fortunately doesn't have these so 2.5l is common here. Below 4 cylinders there are other tradeoffs that generally result in a poor design for vehicles so they just shrink the cylinders.
There's plenty of straight 6 trucks on the road with large bores. They're heavy but they're very efficient! It works for trucks. Then look at what they use in freighters and cruise ships. Big, slow, and 50% efficient. That's about the best efficiency this world has to offer with regard to practical heat engines.
Or you could just build a Boxer 2 with fork and knife crankpin/connecting rod setup. Better yet, since torque twist becomes increasingly violent with displacement, you could use a U configuration U2 engine with two single inline engines with their crankshafts spinning in opposite directions and connected by 1:1 gears with a 0 phase difference in stroke cycles which gives 0 torque twist, and if you move the cylinder and the cylinder head up by the length of the stroke and connect the two piston heads from below the cylinder into a single entity, you can eliminate the friction made from the pistons heads pushing into the cylinder wall, since the unified set of pistons is receiving a net 0 force from the conrods spinning in opposite directions. The crankshaft balance weights completely cancel out the forces at TDC and BDC and the two balance weights cancel each other's side to side movement as well, though the secondary vibrations still remain since the weights are traveling in circles and the pistons in lines.
Great video! I loved the explanation of how increasing the compression ratio improves thermodynamic efficiency. I couldn't help but notice that this 5-stroke concept is very similar to the triple-expansion piston steam engine with its 3 cylinders used to extract more energy from the steam than a single cylinder. This was the most efficient incarnation of the piston steam engine before it was made obsolete by steam turbines with their higher efficiency and simpler design.
It is sad to see an innovation like this just not pan out into mainstream. The Wankel was along the same lines. It turns out, with mass production, you cannot really beat an inline 4 stroke engine with a small turbo pumping known quantities of air pressure into a computer controlled fuel injected engine to be able to produce desired torque at RPM.. All while complying with US California emission restrictions. EVs will take over eventually, the ICE project was such an amazing and wild ride. I loved the whole progression.
"you know, stuff like... twice the balls, half the hair" 😂 I literally Laughed so hard I shot coffee out of my nose at that line!
And the commentary at the end was brilliant, thanks D4A!
Do you know what the word literally means?
@@keithc5729 Yes, I LITERALLY do, and I LITERALLY shot coffee out of my nose... vs. virtually or figuratively.
A real engineer, grounded in real experience. There are not very many of us left in the world.
Huh? There are probably more people in the world who are engineers today than ever before!
@@devilsoffspring5519 As an Engineer that works with other engineer's, there are not many with common sense. Many are copy/paste and have no idea what they are doing
I've worked with quite a few good engineers, and known others socially. If you don't know many, that sounds like a sample problem.
D4A is a political scientist not an engineer
Most modern engines already do this "fifth stroke" by the use of a turbocharger, the exhaust turbine extracts energy from the hot exhaust gases which gets transferred into positive intake pressure which pushes down on the pistons during the intake stroke, does the same thing. Plus of course you can change the operating parameters of the turbo on the fly, from low boost operation using only the expansion energy and increasing engine efficiency, to high boost operation for a large increase in torque on demand (at the expense of efficiency via an increase in exhaust backpressure, but you can't have everything).
Heavy Diesel engines have also used an exhaust turbine to add torque directly to the transmission exactly the same way.
It's just much simpler to fit a turbine to the exhaust than add an extra cylinder to the block just for this second expansion.
I just wish there was a way to know the orders of magniture of these forces and energies.
@@seriouscat2231 There is, it's called engineering.
@@BigUriel, where should I go to look for this… engineering?
@@seriouscat2231 Get a book in thermodynamics that gives you the equations for various cycles which allows you to calculate the indicated work done. Of course this isn't something you can learn in one afternoon, people get masters degrees on this stuff.
Then you have to factor in mechanical losses. Those are very hard to calculate and you'll mostly just have to look up empirical tables of typical figures.
OEMs just use FEA computer software that tells you everything about an engine's performance with pretty high accuracy. These are expensive and difficult to learn in their own right.
Makes me think the best 'enhancement' of the 4 stroke engine ever designed was actually Honda's Variable Valve Timing. Rather than 're-inventing the wheel', Honda very wisely took one single aspect of it and applied new thinking (and technology) to produce something genuinely useful. Honda truly is a visionary company.
BMW has infinitely variable valve, duration and lift allowing for the n52 engine to run without a throttle body
It's kinda obvious that after fuel injection, turbocharging and VVT there are no economically feasible enhancements left
Fiat were the first manufacturer to develop VVT. Obviously there are lots of different systems to achieve the same basic result and Honda's version is unique but certainly not the revolutionary leap forward you seem to be making it out to be.
@@carloslara7452 honda perfected it 1st. They have insane engine designers. Look at the s2000 engine.... for its time crazy engine. My perfect car would be a toyota build with a honda drive train.... but not sure abouyt the transmissions.... honda trannys are a bit weak.
Can you cover the adiabatic engine built by Dale‘Smokey’ yunick.
Thermal efficiency was purportedly higher than today - could be bogus but it would be nice to see what you unearth on the subject.
Thank you D4A !😊
As a 4 stroke guy, I can assure you 4 strokes is good enough, it’s not the number of strokes but how you use them.
😂
Different strokes different folk
Despite what you say, that's not actually significantly better than being a 2 stroke guy.
@@jonc4403😂😂
But can you do 1 stroke?
My Miller-Atkinson 1NZ-FXE engine likes this video.
It wasn't quite as unsuccessful as we might think. Steam engines. First conceived perhaps a century before Otto's idea, it started actually being commonly used around the same time and may have been where Otto got the idea. That continued for a very long time in ships slowly being phased out around WW2 for the far more powerful turbine engine and/or diesel. Triple expansion was likely the most common method, but it works exactly like this engine here. A high pressure initial cylinder, that expands to a larger lower pressure cylinder, again expanding in the final cylinder before being exhausted often at around atmospheric temperature. The benefit was the same too - efficiency. It was remarkably successful and has obviously demonstrated that the idea has merit if the size and weight allows.
Maybe we will continue to see such engines in heavy diesels like semi trucks where the size and weight is a small fraction of the total vehicle and trailer, where fuel costs are an important financial factor, and where high load constant RPM conditions make up a high proportion of usage. We have to hurry though, in a only a couple of years the multiple expansion piston engine will be 250 years old!
D4A been really silent.
I thought this might be a bot that copied someone else's comment because of the girl in the profile picture, but it actually seems to be real.
@@nathangamble125 No, it's my own. I'm a physicist so I tend towards detail oriented comments. Plus I've obviously got an interest in engine technology and engineering in general.
The thing is you can accomplish the same thing with a delayed intake valve closing without a custom engine block.
Oh, and she's "detail orientated", great now I'm depressed
I wonder if that kind of extra cylinder(s) would make sense on ship diesel engines. I'd imagine those run most of the time at specific rpm so you can design for that specifically. Ship diesel engines are 2-stroke engines so I guess with extra cylinder(s) they would be 3-stroke rather than 5-stroke, but still.
Love this guy!!!
The Verbund motor sounds like an analog to the double and even triple expansion steam engines (piston, 2 stroke). Exhaust steam from the small diameter, high pressure cylinder flows into a larger diameter, low pressure 2ndary cylinder. Of course, steam engines tend to be run at a rel constant speed.
35% sounds like a low efficiency, but the average power plant runs on the Rankine cycle and gets 30% - 35%. Most of the power used by EVs comes from Rankine cycle plant. The state of the art for proven heat engine performance is the combined cycle. Rankine cycle dates back to 1859, or 165 years ago. Coal plants, gas plants, nuclear plants and part of combined cycle plants are burning and churning out power with this tech. Also - I drive a 2021 Tacoma with a 6-cyl Atkinson engine. With the right tires and 100% gasoline I can get 26+mpg. As a side note - when engine stats are quoted I always wonder if the engines were fed 100% gasoline or ethanol contaminated gasoline.
Toyota's new generation hybrids are getting around 40% these days
This is a peak efficiency, only achievable at low RPMs and full throttle. This is one of 2 main reasons diesel engines are more efficient than petrol ones - they don't need a throttle and can instead reduce the amount of fuel being injected. Petrol engines cannot ignite a mix that is too lean, so they need some kind of air flow restriction.
@@Appletank8 The one which made headlines with 41% were lab results. On the diesel side TDI do 43% in the lab, that was over 20 years ago, though.
Have you done a video about ceramic cylinder coatings by any chance? May be interesting to know why despite the great promise it went nowhere. Thanks for your super interesting and well-researched videos!
"why despite the great promise it went nowhere"
You mean why the big promises made by snakeoil-salesmen and other scammer never materialize?
Ceramic is hard and can withstand high temperatures but it's also very fragile, so vibrations, big changes of temperature in short time, impacts, etc, can break it in little time making it unsuitable for production engines.
Wasn't it used on BMW cylinders as surface finishing? I much prefer the chromium based ones anyway. I've used those since when I was a kid on my 2 stroke bikes...
Were you thinking of Nikasil maybe? I don't think that was ceramic based? Anyway the (promised) ceramic advantage was much less heat transfer to the block. I think there was even talk of ceramic (coated) pistons too.
I love your channel ... but can you please use a black or grey background? I'm watching this video in bed, and I'm absolutely blind.😅
Try the “reduce white point” setting in accessibility
@orapasc I'm watching from an android tablet with an oled screen. I don't have a reduced white point setting, but I do have the option extra dim on. Even like this, modern oled screens like mine also have a very low refresh rate in low lighting settings, which gives some people head akes and perturbs sleep. I dont have any of the symptoms, but even at the lowest lighting, I still find the background annoying. I think only Oneplus screens from the latest generation on tablet and flagship phones have a high refresh rate, which is said to help with low lighting watching comfort. Oneplus is a fairly common brand, but it's not Samsung or Apple. So their products are rare and have quirks to them(thats why I don't have any them). This is a simple issue that can be fixed in post while editing the video by changing the shade of the background.
Brightness down
@@DavidSadloski Read the reply above ... it was at minimum.
@@transc3ndus yea no I didn’t read that. But now that I know that, just don’t hold it 2 inches from your face. Problem solved.
Great program. Great graphics and presentation. Internal combustion is best. Fill tank, drive for 700km. Fill up tank (5 mins), drive another 700km.
Couldn't agree with you more. But we are where we are. If I remember correctly, 60% of US car journey are under 6 miles, 95% under 31. But everyone wants to be able to drive literally all day without stopping, or to take a multi ton electric truck to buy a bag of oranges or drop Johnnie off at school. America has emitted more CO2 than the combined populations of China, India and Japan. And exports more oil than Saudi Arabia produces.
Similar to what Thomas Edison said, we didn’t fail to make an engine. We learned how not to make an engine. Every step for the last 150 years, whether proceeded or not has left us with very powerful engines at very reduced emissions in smaller sizes.
*Genuine question* why don't we spin up a turbine with the exhaust gas that runs a generator and that runs electrical assist / charges batteries
F1 used to use that...MGU-H
It's prone to failure and electrical issues.
@@S.ASmith Interesting - Ill look it up. It was one of those things that seemed so obvious I thought I was being really stupid asking the question.
Because it's a lot cheaper to just put the alternator on the fan belt.
Because it's already a thing and it's called an alternator but it runs on the serpentine belt instead of exhaust gas. The exhaust turbine one already exists and that is called a turbocharger! It doesn't generate electricity but makes an extra boost for the engine which creates more power.
@@Kelle128 "makes an extra boost for the engine which creates more power." NO IT DOES NOT. The additional fuel you can add as a result of the increased volume of O2 is what increases the power. NOT the turbocharger.
25:30 I wasn’t going to mention it but the electric motor was invented in the 1830s…. What has changed recently isn’t the motor as much as the batteries to store the energy and the power electronics to drive them more efficiently.
Misleading. Brushed electric motors were invented in the 1830s, and are still common; but most electric cars use brushless motors, which were invented in the 1960s.
The design of both batteries and motors (at least for the types of motors used in the majority of electric vehicles) have fundamentally changed since the 19th century, while the design of 4-stroke engines used in the majority of ICE vehicles has not (unless you count direct injection as a fundamental change, but that dates back to the 1920s so is still much older than brushless motors).
The electric motor has seen some massive improvements like brushless designs, but the original design is still used in a lot of cases. The electric motor is FAR more versatile than combustion engines. But if I can I will usually choose a combustion engine over an electric motor.
15:30*
also electric engine didn't stay the same
they changed even more than an ICE
@@nathangamble125 brushed motors were not as common as we'd think, brushless is quite old as well and far more common in the industry, once we adopted alternative current as a standard it was cheaper and easier to produce synchronous brushless motors.
@@nathangamble125 Commutator free asynchronous motor was invented 1887, that tech is also quite old it just so happens when they figured out the physics of it they could not quite make it happen with tech they had. What most electric cars happen to use is permanent magnet synchronous motor, you could not use that without DC to AC converters with variable frequency, which would say biggest hold back was electronics for currently used motor as it just so happens they wont start on there own and 100kW is no small amount.
Not to mention and when talking about induction motors they are about 90% efficient, so the jump to synchronous motor at best is 10%.
And brushed motor goes at 75%, so truly what has changed the most is batteries and electronics. Oh and don't forget all the improvements ICE got from electronics.
And still to this day what holds electric cars back is batteries.
The "Verbund Motor" is nothing that was invented newly. It was already used on steam engine with tripple expansion engines.
Verbundmotor with an additional turbine at the end also saw wide commercial use in the early 20th century, yet modern ships don't use them. Tubo-diesel engine have just become to good.
0:00 🚗 Internal combustion engines are not very efficient, with modern gasoline engines averaging around 35% thermal efficiency.
0:51 📉 The inefficiency stems from all engine strokes being of equal length, with only the combustion stroke producing significant energy.
3:01 📈 Increasing the compression ratio can enhance engine efficiency by allowing more time for energy harnessing during combustion.
7:12 🔄 The Verbund Motor utilized in the past added a fifth stroke, "extended expansion," using exhaust gas energy to boost torque.
9:11 🏎 Ilmor Engineering, known for high-performance engines, developed a five-stroke prototype showing promising fuel efficiency and power.
13:12 ⚖ The five-stroke engine faced challenges with varying exhaust gas energy levels at different engine loads, impacting efficiency.
15:54 🌱 Despite its potential, the five-stroke engine struggled with emission standards due to slower catalytic converter heating.
16:43 🕰 The conventional four-stroke engine has persisted for 150 years, resisting many attempts at disruption due to its reliability and efficiency.
15:17 okay but it does depend on number of cylinders firing, right? Modern engines run on reduced number of cylinders when power output is low. Passive cylinders could even act as those exhaust receivers actually.
Very interesting content well presented. Thank you.
ICE engines have done a lot for humanity. Long live the ICE.
And they will continue to. EVs are a fad and have already peaked. It’s all downhill for them..
2:59 Indeed, if this were not true - that is, if the piston was responsible for pushing out the exhaust - two-stroke engines could not exist. I hadn't really thought of it this way until now but yep
And two-stroke went away, for vehicles, as you have to inject the lubricant (oil) in with the fuel which leave all kinds of extra nasty shit coming out of the exhaust pipe... But that Kawasaki "Two Stroke Screamer" was scary fast and powerful... friggen accidentally pulling wheelies in 4th gear...
@@garrettmasarik8012 Twice as many bangs per rev
@@garrettmasarik8012 given the technical nature of the channel someone (so might as well be me) will probably point out that while almost all two-stroke designs also require oil either premixed or injected, this isn't inherent to running a two-stroke cycle. It is possible, and done in rare designs, to run a two-stroke cycle and also have an actual oil system such that the fuel can be just fuel.
I'd enjoy very much a video on the topic to round out my limited understanding. Afaik the main reason this "couldn't" be done is two strokes allow for ports which don't decline in performance under dirty combustion (which two strokes seems to inherently involve, oil or not?) like valves with their tight tolerances. And, I guess, we could probably do a pretty sweet job designing one to work great now, even with an oiling system and valves, but emissions regulations make it so niche it's unlikely to get worked on.
I am extrapolating a lot here and I'd love for the channel itself to touch it
@@JoshWalker1 Exactly. The reason most 2-strokes need oil injected with the fuel is that they are using the crankcase as a supercharger. Put an external supercharger on it and you can have a sealed crankcase just like any 4-stroke. A modern sealed crankcase direct-injection 2-stroke could potentially be a very useful engine, and just as clean as any 4-stroke.
@@DABrock-author My limited understanding has a hole in it! Elaborate on the "crankcase as supercharger" bit??
Every 4 stroke motorcycle engine I’m aware of opens the exhaust valve way before bottom dead centre on the power stroke, so wastes some of this stroke, presumably sacrificing efficiency for maximum power. My Triumph opens its exhaust valves 43° before BDC. If I recall correctly after 50 years, my Ducato Desmo 450 motorcycle opened its exhaust valve 90° before BDC. It seemed remarkable then, and now.
Separately, the compression depends not only on the compression ratio, but also on when the intake valve closes. My Triumph, with 12.92 nominal compression ratio, runs on 91 octane standard unleaded (in Australia). The previous model with a lower 12.25:1 compression ratio requires premium 95 or 98 octane. I think this is because my bike has different valve timing, with later intake valve closing on the compression stroke.
IanB
The irony of the situation wasn't lost on anyone in the room.
I'm no engineer, but I wonder if cylinder deactivation on the middle cylinder would improve low RPM efficiency. Add a secondary air system to warm up the cats and maybe this would be a feasible design 🤔
As far as cylinder deactivation, I was thinking the same thing. Maybe use a similar concept to variable valve lift and shut down the low pressure cylinder, or at least limit its travel, with hydraulics and/or solenoids.
I was thinking of giving the middle cylinder a fuel injector that only operates at low rpm. Something to give it just enough extra combustion to justify its weight until the outer cylinders are making enough pressure for the middle injector to shut off.
Cylinder deactivation would do nothing as there are no pumping losses in the 3rd cylinder, only gain. The friction is what you want to reduce and for that you'd need to physically disconnect the piston/rod from the crank. Ain't happening in any reasonably efficient way.
You're obviously not familiar with the KISS principle.
"And let me know when ANY kind of propulsion technology manages to last 150 years, thank you very much." That is an easy one. The bicycle!
Also, Wikipedia says the first electric vehicle was built in 1881, which makes EVs just 7 years short of their 150th birthday.
Legs:
Sails. Oars. Speaking of ocean-going propulstion, steam boilers started
The mighty horse...
The details vary on when you think commercial use started but electric motors and four-stroke engines have been used commercially for about the same amount of time.
The future, as they say, is in the details.
Who else tried to wipe off the black spot from their screen? lol
I ran my cursor over it thinking I'de lost some pixels.
Congratulations, great job in investigating rare topics and very instructive in its presentation. May I suggest a video on Miller cycle engine, I heard of it, Mazda and Toyota once used these, I’d loce to hear more. Thanks so much for your great work
As usual, you have a marvelous delivery, & always deliver a well spoken technical description of your subject. Thank you for your delightful & informative video. I never fail to learn SOMETHING from your treatise. Cheers! from the windswept Prairies of Alberta Canada.
There's no replacement for combustion. So long as there is no true evolution in other technologies (wich doesn't exist until companies see a real profit and even then they do the bare minimum and try to force it on the market, instead of making something usefull and effective) there will be nothing else to replace a running, reliable, efficient system. People always talk about how inefficient a combustion engine is pointing out heat loss, but they fail to mention that a 1.000kg car can travel 500-700 km before refueling for 2 minutes, while staying reliable in any weather conditions. Also people like to ignore the fact that combustion engines continue to become more efficient. For the moment being, any alternative to gasoline or diesel is simply a marketing gimmick of a fun, expensive, hobby-technology, that is not suited for real world daily use.
I think it would be better not to split expansion phase on two cylinders, but separate intake and compression to separate cylinder. So one smaller and cold cylinder makes intake and compression and then pushes the compressed air to another one where it burns and expands. That will give a lot of benefits because fresh air will not heat up from the cylinder walls before burning. In the same time expansion cylinder can be much hotter, that reduce the thermal losses. Also intake piston can be made lighter as it works with lower pressure, that will decrease the mechanical losses. Or it even may be replaced with another kind of compressor, like rotary, connected to the crankshaft with a variator to control the power instead of a throttle.
The only problem is to push the compressed air from one cylinder to another fast enough. So that might limit the RPMs. Or we need to close the exhaust valve and start exchange the new air earlier, that means there will be still a lot of exhaust gases. But that is good for NOx reduction.
I place my bet on a electro dynamic turbo/compressor which doesn't use exhaust gasses or is belt driven. Instead it will be fully electric and uses the signals from TDC- and TPS sensor coming from the ECU. Lots of benefits here!
Good work! One day, when i have time, i need to learn how to disassembly one of these motors. Thanks for sharing 🎉🎉
5:07 though (regarding the revs that Diesels can't rev as high) I would humbly add that not only is the mass of all components in a Diesel higher which will clearly have a negative effect slowing down moving parts as a result of component inertia somewhat, but Diesel engines also operate on the principle of self-ignition, where the diesel fuel is ignited by the high compression of the air-fuel mixture in the cylinder without the need for a spark plug. This requires precise control of the injection timing and a relatively longer time for complete combustion, especially at higher speeds. As engine speed increases, the diesel has less time to fully ignite and burn. This leads to inefficiency at higher RPMs and can, or will, cause the engine to knock. By comparison, gasoline/petrol engines can precisely control the ignition timing through the spark plug, even at higher speeds, allowing them to operate more efficiently at higher RPMs and subsequently reach much higher RPMs.
Your videos are great. You explain mechanics so efficiently, including everything that is needed in the proper timing and complexity. Great stuff! Subscribed/Thumbs up!.
just an idea, but what if we just take a inline 6 cylinder engine, do combustion in every cylinder at low rpm / a setting in the car set to power, and at high rpm / a setting in the car set to efficient use 3 of these cylinders for the 5th stroke of the other 3 pistons? Anyone wanna try this idea with me? I really think this could work, the only thing is that you would compulsory need free valves to keep the (I'm gonna call it overflow-valves) closed and opened at the right times. What do you guys think of this idea, could it maybe be practical or are there any problems with it? please write feedback i wanna hear y'alls opinions
Good idea but how do you manage the completely changed gas paths that are needed for this two modes ?
Liked, because the video was very instructive while easy to understand. What I missed was a discussion of efficiency in terms of expansion ration, "time to work" is a bit vague.
My first thought when I saw the cooler exhaust feature of the 5-stroke was: "Doesn't the exhaust *need* to be kind of hot?" And I wasn't wrong.
We saw issues arise when gas heating appliances (water heaters, forced air systems) were made more efficient. Suddenly vent pipes needed to be stainless steel and have condensation capture/disposal systems because the flue temperatures were below dew point for the moist flue gasses.
I take one issue with the “caveat” about the engine size argument. Yes, adding the extra low pressure cylinder accounts for size purposes but only the two high pressure cylinders count for volumetric calculation purposes. The low pressure cylinder is in-line with the high pressure ones so it doesn’t do anything to affect the volume of air being cycled into or out of the engine as its purpose is completely passive.
I’m seeing this as a kind of “reverse supercharger.” Where a traditional supercharger takes mechanical energy from the crank to pump additional air into the intake, this concept takes energy from the exhaust gasses and turns it into mechanical energy directly into the crank.
If your only concern is extracting as much energy out of a unit of fuel as possible and you have few or no limitations on space, this kind of design can make a lot of sense, particularly when paired with other efficiency-increasing techniques like turbocharging.
Very interesting video. Many thanks for that!
BTW: Having high- and low-pressure cylinders was very common on steam engines in the late 19th century. Even machines with three or four stages were invented and build.
And now we have EGR systems Mucking up our 2nd cylinder and injector.
Most modern engines use variable valve timing tricks to keep the intake valve open as the compression stroke begins. This stores gasoline fuel in the intake manifold. This allows the combustion stroke to be relatively larger than the compression stroke, extracting more energy. Then it exhausts, and the next intake stroke draws the fuel-air mix back in from the intake manifold, along with new air, plus additional fuel being injected. The consequence of this is the compression ratio is lower, thus the power output is lower; but it does draw more of the energy out of the fuel.
Fascinating, thanks for this! I’d never heard of this engine type before (and I used to be a mechanical engineer). I guess this engine type would only be practical for situations in which the engine was constantly performing near peak power output. Maybe for aircraft?
Haven't watched a D4A video in a long time, but as usual, a great presentation by the host (and he has improved himself greatly from some of his earlier videos) of a interesting subject. What I find most interesting is that the early pioneers of the ICE were aware of the inefficiency of the design and were already doing something about it. In their day of low RPM agricultural work primarily, it was a technological marvel and answer to the drawbacks of a period ICE, but in our high-tech, go-fast times, it has its limitations.
How about a two stroke engine?
Inject pre-compressed air and fuel, then instantly burn (1), then exhaust (2).
If you inject fewer air and fuel, you will get throttling for free and more expansion.
you can even start the motor from a dead stand-still (provided a cylinder is in the right position).
pre-compression could be done by the engine during breaking.
it might even be possible to switch between 2 and 4 stroke with software-controlled valves. or some kind of hyper-vtec.
You could get some adjustment for varying load by varying the amount of air allowed in during the intake stroke. Then, use a diesel version of these engines in applications in which most of the operation is at constant speed and load. Oceangoing (and even Great Lakes cargo ships immediately come to mind -- these run at constant speed for days or even weeks at a time. The one extra complication is that you would need extra provisions in the valve gear to be able to run the engine in both directions, since most cargo ships have direct drive from the engine to the propeller, and so this is how they back up. But i you could improve their fuel efficiency from the current ~55% to ~65T, it would be worth the extra valve complexity. The long running time of ships would also mitigate the catalytic converter warmup time, although I haven't heard of ships even using catalytic converters in the first place (but it might be in the works, to meet future pollution regulations). Another option is to split up the catalytic converter and put in the tubes from the high pressure cylinders to the low pressure cylinders, although that might be TOO hot. Also note that if you put in a bypass to let the high pressure cylinders temporarily exhaust to atmosphere, you can make the compressed air starting sequence very easy -- just feed the compressed air into the low pressure cylinders, and you don't need to have as high a pressure to be able to start the engine; then once it gets up to speed, cut out the bypass and go to 5-stroke mode.
Generators have also been mentioned as a potential application for this type of engine. But we need to be making electricity as much as possible from renewable energy sources, whereas you can't run electric trolley wire over the ocean, and batteries don't have enough capacity; sails, on the other hand, could serve for part of the journey, but you are still going to need an engine for long parts of many journeys. Still, it wouldn't hurt to have some of this type of engine on standby as emergency generators in case of a dropout in the renewable energy generation.
Compounding turbo doses the same thing, (Down flow Turbo that’s connected to the engine crank shaft) please make a video on a Down flow Turbo. Great video!
so basically the reason for fail of 5-stroke engine is the same as for split-cycle one...
It has some great advantages in very narrow rev range, so it remains theoretical construct in real world of permanently changing load, rev, and any other parameter you might think
Great, comprehensive video, as always