I’m a big fan of rotary engines and the Liquid Piston engine intrigues me for being a clever way of putting the Atkinson cycle into practice but I agree with you, it still needs improvements to become something that is universally better than the piston engine.
It looks like a very promising design for the dirt bike industry, as longevity is a much smaller consideration. Many riders rebuild their engines after much less than 1000 hours, especially racing. The power density, low weight, and relatively simple construction would be very convenient in a high performance engine for dirt bikes. And rebuild/overhaul may be easier due to the fewer parts. Plus, they sound amazing which tends to be popular in motorsports. Admittedly, the low torque could be detrimental, but gearing would likely be enough to compensate for that in such a light weight application as dirt bikes.
Was optimistic about this engine for a while, but just like Achates Power, they unfortunately seem to have become one of the countless entities that promised to "change everything" but ultimately delivered little or nothing.
I agree. Knowing that d4a is a self taught RUclipsr makes me look at things like this now differently. This one and the one cycle motor are not realistic for most people if they ever come for sale.
I mean I think you have to consider a bit broader view of these things. Any new engine has to compete with the already existing units that have absolutely insane amounts of cumulative development spending behind them. So already from the get go it's super hard to be competitive. However many of these concepts such as for example the Achates double piston engine should be able to be competitive. The issue is just that due to all that EV nonsense it's totally uninteresting, unhip and also not supported by the state to invest into anything like this. If you ask me, we first need a resurgence of appreciation for combustion engines to set the plane to actually get people to build and invest into these new concepts.
I very much appreciate how you talk about both the ups and downs, instead of focusing on one or the other. Whenever I hear of a new engine technology, I'm always excited to hear your views on it because of your balanced and fair analysis.
I second that. Way too many YT channels just excitedly repeat all the nice things a company's press releases say about their new product (that needs funding and buyers), with absolutely zero critical analysis.
Finally, an analysis of this engine that doesn’t feel like paid marketing, nor is a video just crapping all over it because it’s different. It was great to see someone actually gather all the numbers together and go through them in a comprehensive video. I’ve followed this engine for a while and knew something had to be up with the engine for LPI to have been stuck in ‘development’ for so long. Thanks for pointing out the longevity and efficiency figures as well as the most glaring weakness in the crankshaft.
@@a-iz4pg I usually criticize video's pretty severely but you seem to be making unfounded comments? D4A has been overenthusiastic a few times ( which I have commented on) but pretty sure he's not a shill.
One added benefit over the Wankel engine that I don't think you addressed is that it heats up more evenly. One of the problems with the Wankel is that it only fires on one side and will shift and deform because of that.
Don't know if it's a realy problem, but that x-engine is inverted Wankel engine, so only one side of a piston is opposed to combustion stroke and is heated more than another.
@MaximusU76 - even though only one portion internal rotor face is a "combustion surface", the rotor functions as an intake runner, which facilitates a considerably more uniform temperatures. Also, diesels bleed off about half the surface temperature per kw/hr load because they're more thermally efficient.
The heat distribution problem is inverted: A Wankel has even heat distribution around the rotor (because all faces go through the same cycle) but uneven distribution around the housing (which has distinct areas for each phase of the cycle). The X-engine has even heat distribution around the housing (because each of the three chambers goes through the same cycle) but uneven distribution around the rotor (which has distinct ends for intake-exhaust and the for compression-power).
I think it's my standard comment at your vids: 'When I think I know it all, something clever and new comes up." How interesting and what a clear explanation again. Thanks!
The diesel may be better in a uav due to higher efficiency resulting in longer loiter time, and not having to shield electrical noise from the ignition system.
the diesel version should be able to run on road diesel and jet A. The military isn't going to want to carry around a few jerry cans of pump gas just for this
But compression ignition with diesel means you get loud diesel clatter and smoke. You have to remember, this engine still needs to burn 2T oil for apex seals like a conventional rotary. The enemy will see you from a mile away because of the smoke trail . Maybe UAV with this engine can be used to spray pesticide for agricultural use, or maybe mosquito fogging , but not stealthy enough for military use.
This does sound very useful for military applications. Definitely very compact, and if it is quieter, that’s also a nice bonus. On the logistical side of it, you can ship a bunch of them out, and pick up the broken ones at the same time, and you’d just need one state-side facility to take in all the spent engines & rebuild them & put them back in circulation. Maybe also could be useful for camping or wilderness trips since it is so small & light, but the reliability becomes an issue then. Very interesting little engine.
I already mentioned this in few videos. In Finland moped is defined as no more than 50cc and around 5hp well as cant move faster than 45km/h. Since we have engine size limit and changing gear ratio's make first gear ridiculously slow with high torque and make engine in 5th gear scream, or 1st being with out torque and 5th gear being reasonable, low capacity max50cc, high torque diesel would be ideal and its easy to limit mentioned speed, but with ability to torque trough steep hills and have cheaper fuel source, but there havent been any diesel engines compact enough to retrofit into older moped that dont have emission bullshit. Witch only dirty the engine and eat power. Despite what he said, emissions are not a issue, least when retrofitting engine to older moped and who wants the modern plastic trash anyways? Two strokes need rebuilding time to time and kids tuning them up with out knowing what they are doing, so rebuilding them aint problem ether. Long as engine is light weight diesel with more torque than same size 2 or 4 stroke engine, that can last same as two stroke, easy to fix and rebuild and cheap to purchase, it would be hit. Too bad they are not yet selling them anywhere. Wankel would be another nice engine, but there too you cant find 50cc ones and even then the larger ones are hella expensive regardless of condition.
I'm into paramotoring, ultralight form of aviation where we carry the motor in our back. What we want: absolute most power out of least amount of mass and space. Also, as we have "a lawnmower" in attached in our backs, it is nice if it does not vibrate that much. The drawbacks of the liquid piston would not be problems in this sport: - *Longevity:* Our current two stroke engines last ~300h anyways before full rebuild. Something like 1000h would be a dream - *Torque:* Propeller does not need it - *Difficult to mass produce:* Our current motors are hand crafted and expensive anyways. - *Poor emissions:* Haha lol, not on list of priorities :D. The paramotor is practically a large fan that blows the fumes away from self anyways
Also, this thing can burn many different fuels. It can be made to burn anything from hydrogen to diesel. Of course it'll have different performance characteristics depending on the fuel.
So UAVs _and_ paramotoring. So I guess the takeaway is that this engine would work for: - Flying vehicles without people - Flying people without vehicles
Thank you for a very level-headed breakfown of something that the media tends to oversell. Really love the work and the good engineering approach to these subjects.
This channel has taught me a lot, I am proud of the fact that when they said the crankshaft supplied the air mixure my first thought was "that's not gonna mix well with lubrication".
As always, spot on. Great explanation. I am a mech designer, with some hobby affinity with engines. For my dad it was his life. He would have enjoyed this a lot! It is an art in itself to explain complicated things simply. You 've got it!
This is the best video I've seen yet on the X-Engine, bravo! I was not aware that they were trying to shove air through the crankshaft, I had just assumed there was a divider in the center of the rotor so they could push air in one side and let exhaust out the other. That seems like something they're going to need to fix before they can make much progress on commercialization. I understand the amount of rotor surface area that's exposed to combustion poses a big heat management problem and makes it challenging to turbocharge. Of course if you could turbocharge one of these then the power/weight would be up into the turbine realm and even 30% efficiency would be a huge win for aviation.
Extremely interesting concept and I believe you have accurately predicted its future. As always the speed, clarity and accuracy of your presentation is superb. The text of your presentation caps it off, allowing time to absorb the subject in depth. Many thanks.
This the most comprehensive and realistic explanation of this engine. In the end, the same core defficiencies will doom it to the wankel’s fate. At this point, it is diificult for any “new” internal combustion design to out perform existing ic technology that has the benefit of over 100 years of progress.
@@Appletank8 probably, but the discussion here is about car engines. Turbines were tried in the 50’s and 60’s and didn’t work out for land vehicles. They definitely would not meet emission standards now even if the other problems were worked out.
@Appletank8 it kinda maps the same as warships, they went from steam piston engines to steam turbines, aircraft too went from gasoline piston engines to gasoline turbine engines. I feel like pistonless engines other than turbines are just re inventing the wheel by putting feet at the end of spokes...
@@Appletank8 microturbines are gaining interest again, and for good reason. Turboshaft engines can be tremendously efficient and incredibly power dense, but making a muffler for them is damn near impossible. Some guy put a boeing turboshaft in a Miata and gets like 70MPG with it, but it sounds exactly like you'd expect a Miata sized Boeing to sound like.
For the (sealed) Crankshaft Support Bearings, you would hope that these Bearings have been filled with High Temperature Grease - when operating at those temperatures. The 'normal' grease in many bearings would simply 'run-out' very quickly, leaving little or no lubrication. Mind-Blowing how this guy can study all engines in complete depth, and even their shortcomings in design. I'd like to know what car he drives.....because it has probably got the best-designed Engine!! Greetings from Australia
The problem is less lubrication and more heat build up. Using sealed bearings and with no cooling available there is nothing to cool the surfaces so there is no way to control heat. That means either massive tolerances - which leads to massive wear and innefficiency - or as it seems here a need for replacement every 1000(!) hours which in reality would be a lot sooner especially if it was heat cycled often as most car engines are a couple of times per day.
I don't see why forced oil lubrication / cooling couldn't be used with this design via using 2 oil seals per side and using a feed and outlet port from the housing into / out the bearing?
@@Samqdf Have a think about the complexity and amount of sealing pieces it would rely heavily on. Then remember we're talking about mass production tolerances. The failure rate would be through the roof.
I always wonder instead of a passive apex seal, couldn't you use a piezoeletric actuator to maintain seal without lubrication. Given in regular piston engine, the gap between cylinder and ring is around 50 microns. A typical piezo actuator has travel length around 100 microns with resolution around 0.5-1.5 nanometer and response time around few microseconds. So you could have a active apex seal that continuously monitor the distance between rotor and stator and maintain a few nanometer gap without lubrication, thousands of times per second (0.5-5 response time, so about 1mhz position update frequency). In an active seal system, it also solve another issue where uneven heating of the engine chamber create larger gap, since the actuator seal will just compensate for thermal expansion and increase the travel distance. Piezo actuator is pretty cheap too, around 4-5 bucks each. So cost shouldn't be too expensive. Modern HDD hard drive use such piezo electric actuator at its magnetic reader head to maintain the nanometer gap above hard disk. The reader head actuator can move at insane speed with equally insane acceleration while compensating for thermal expansion of the disk time in real time. And it's done at a commoditized price tag. Similar piezo actuator technology should be able to transfer to apex sealing environment to maintain a way smaller gap and needing much less or no oil. Since the tolerance for a hdd drive gap is way smaller than a piston ring gap.
now add wires. add heat. do it 200 times a second. sensors. connections. interfaces. software. hardware. this was apex seals right? mounted in a rotor? that spins on bearings? and then spins on an eccentric that also spins? keep wondering ;)
This seems possible, PZT (Lead Zirconium Titanite) which is most common, has high temp resistance. Especially if the actuator in question worked in conjuction with a simple analogue circuit.
@@paradiselost9946 Well, remember the X engine (stupid name lmao) operates with fixed apex seals, and not rotor-mounted apex seals. So the wiring could go to a remote module and the piezo actuator itself would be housed in the block, not the rotor.
Thank you for the well prepared video ! Big kudos for having also very committed community who are willing to watch 20 minutes with enthusiasm and a lot of comments 😊
Thank You! In my opinion you have the Best explanations of engine tech in a way that the average person can understand! Detailed, accurate, reliable info! I rate you #1 on RUclips!!!
Incredible video. I know nothing about ICE’s, other than their general theoretical function, but I accidentally stumbled upon one of your videos some months back (🤔 Scotch yoke engine!), and I’ve been hooked. Your explanation and analysis is thorough, concise, well-explained and totally fascinating. Just a winner of a channel. Outstanding work, thank you. This motor… could it be deployed in a motorcycle…😳 …maybe a diesel bike
Thank you so much for the kind words. Motorcycles are also subject to stringent emissions nowadays in most markets so I doubt chances are high. Plus, current engines are simply very good. You have small and lightweight parallel twins delivering everything anyone could ask for.
@@d4a🤣 Of course, I paused the video to type the comment… and as usual, you are covering it all very thoroughly. As a biker, I can say you’re spot on- he parallel twins today have been able to be efficient, strong, slim and light, and the vibration balanced out enough to be so versatile. Hondas are particularly good; I had a new CB500F, and plan on buying an Africa Twin, and both are fantastic. The V is still the “ideal” for a bike, though… for feel and character. I had a couple of Italian Aprilia bikes that were just a joy to ride for the feel… Thanks again!
The military has been trying to get diesel motorcycles in their fleet for years, the idea being that they only need to have one fuel for all applications. Kawasaki KLR Diesel was the closest they came. Enfield of India tried it too for a while, and as pointed out, the military doesn't care about emissions, so it could be a possibility in the future.
Liquid Piston is actually focusing on investors just like yourself on Facebook. People who are not very knowledgeable about this subject. So I wonder if the technology was so wonderful wouldn’t they look for investors who are knowledgeable about this category of technology?
@@somenygaard If your insane enough to research a new IC engine technology, you take investors wherever you can find them, and Facebook is full of idiots. The US military answers your question, it's a perfect fit for the Xengine, and they aren't idiots. Xengine? I wonder if they were looking to Musk to invest, if so they are idiots.
One thing I remember hearing about the Wankel is that because insurance is/was calculated based on displacement, there was some disagreement about displacement definition on a Wankel. One side argued it was the entire chamber, the other side argued that it was only the third that did the combustion. The former side won, so the insurance was WAY too high for the fun factor and it turned people off. With the geometrical inversion of this design, that displacement definition matches the power scaling and would assuage that.
I already have an engine design that does all the stuff this does even better with a lot less parts. I'm still working on the emissions issues, but it should be exceptionally good on that regard as well. This concept is interesting though. This channel always provides some good new things to learn.
Looks like a good candidate for the air compressor head - quiet and with good heat dissipation, also no issues with injecting oil. Would stand somewhere between piston and scroll compressors.
A lot of motorcycles use ball bearing cranks granted they usually are not sealed. I think it would be perfect for a bike and if the bearing is easier to replace I would take that tradeoff. My dirtbikes require rebuilds a lot more frequently than you'd think. I also think diesel being used as the primary fuel would also allow the side seals and apex seals to last a lot longer than gasoline because diesel is a lubricant.
@@caboose22320 the issue is less about apex seals breaking and more how reliably they actually seal the chambers off from each other, and lubrication issues. The Wankel has a problem in that the ignition port will almost always leak some air through, and the side seals still aren't as good as piston seals.
@@Appletank8 this is it... a piston ring just oscillates, and only "seals" during combustion when its forced down and out. an apex seal is getting hit with intake vacuum on one side, combustion on the other, or combustion, exhaust, or whatever... never a constant predictable force but a constant change from tilting one way to tilting the other... same nasty approach angle with teh wall of the trochoid itself... side seals have massive sliding frictions, and again, nothing in a rotor has that simplicity of a piston ring being ASSISTED by combustion pressure to seal... i say it again. the only TRUE "liquid piston" is a humphrey gas pump. dont need rings or bearings when the piston is water!
The amount information that this guy communicates in a clear and understandable way is just amazing. If my engineering professors could have communicated as well as this dude, I would have graduated in two years rather than four. This dude should be a politician, he could "enlighten" the masses who require enlightening.
I was deeply concerned about that hollow crank shaft before lubrication issues were discussed! That has got to be the most restrictive and problematic path for intake air to travel that has ever been imagined!
Whilst true there is technically the potentiol to build it with lubrication in there, it will just result in a crankshaft thats larger for the engine output, but i don't think thats an issue here honestly.
rather than the lubrification i'm more concerned about the air temperature the very moment it crosses inside the crankshaft considering it passes side by side with the exhaust gasses and enters a high-temperature nest.
Thank you so much for making this. If this, and other new engine designs do nothing else, they do show that human ingenuity and inventiveness has not yet stopped, also with the 'improvements' to conventional internal combustion engines. Interesting times!
Ive looked at just about every other sites descriptions of this intriguing engine. Yours is by far the best, including the logic of the 'liquid' piston, which I looked everywhere for the reason for it. Thanks
The crankshaft bearing problem (if you can call it a problem) can easily be solved by moving the intake system from the crank to a port on the opposite side of the engine where the exhaust is located and adapting the rotor with a slant port. It may even generate a vortex to mix air/fuel better.
45% thermal efficiency might be pretty nice if it also comes with a weight, complexity, and wear reduction. I also wonder how the gas version would handle a turbo. Or perhaps they could take advantage of the increased surface area that's exposed to the combustion process by having an oversized cooling system, use this engine as an EV range extender, then add a Stirling Engine to extract electricity out of that heat, dump it directly into the charge controller, potentially boosting the engine's thermal efficiency considerably.
THe big thing I can see it working for is in an every day Diesel motorcycle. It's decent power output in a very compact size really sells itself as a possible new engine for a line of motorcycles. A new brand of affordable, older tech parts with a fairly robust, spunky diesel engine for those efficiency gains could do wonders. Also, 40-50 horsepower isn't high in the realms of bikes, but is more than useable. I also expect that number to rise as they possibly size the engine package up. Being 11 inch by 11 inch currently it's still on the small side, and upping to a larger package could help on the power front, and being a rotary helps size down the attached components on the bike. Being able to reduce the extra space required to house the crank shafts, cams and other upper and lower accessories shortens the height, freeing up room for a larger tank, or even room for a small battery bank. Possible (though highly skeptical if it would ever be properly explored) Diesel Electric Bike. Also assuming it has a similar torque curve to most rotaries, and that the compression benefit of a diesel would push peak torque down a bit I would feel comfortable putting peak torque at 3750-5250 rpm. Rotaries are much less peaky with their torque, having very gentle torque falloff up until you hit peak power where it starts to TANK (Peak power is at where torque tanks BECAUSE the torque tanks at that rpm). Would make for a very easy to learn on engine that has consistent pull from peak torque to the redline. Based on peak power torque of 37 ft-lbs I would put peak torque probably at 43-47 ft-lbs (Unsure how the Fuel, Flame propagation and compression ratio would affect how far higher peak torque is to torque at peak power. IIRC Other rotaries are fairly consistent, with the RX8 being something like ~160lbs at 5500 and ~153 lbs at 8500) I also see the option with the extra space available vs a piston alternative to introduce a Supercharger/Turbo, further granting it an advantage over piston bike engines who forgo the option commercially most of the time due to space/design constraints, a lack of need (most engines above 500cc are MORE than capable enough) and a cost cutting measure. Also, turbo bikes are just much less rider friendly, as the turbo lag is much more deadly a consideration. Given that a 50hp 750cc engine is quite underpowered vs most high rpm 750 pistons easily breach 100hp or more, they are larger in package size. I could see a small supercharger on the x4, especially if they can add another rotar to it getting into the 85-100hp range at a very respectable around town rpm range. This is all just speculation at this point, but I REALLY like the possibility of a respectable diesel option in the motorcycle market, Netting us a VERY fuel economical option with VERY long range due to a larger tank and less consumption per mile, while having a much easier time accessing fuel due to the abundance of different fuel types you could plug into the engine. Imagine if your motorcycle got 100MPG(2.35l per 100km) or more, and you could create your own fuel with foodscraps, waste oil or other sources. Not a benefit in the city, but with the size of rural USA, having a biofuel option to help fund going into town for some fun, or just smaller shopping trips sounds like an amazing option to have available. Would cost a premium though as I don't see a diesel bike being popular if it doesn't net at least 80% power of a comparable motorcycle size, due to the FUN factor a large quantity of people buy them for.
Well you're the first one that pointed out the shortcomings I have been talking about ever since I've seen the design - emmission due to lubrication and longevity due to seal type. I even talked about it in class (I am an automotive teacher in Celje). And you explained so much more!
If this engine turns out to be suitable for UAVs it might also be suitable for light aircraft, at least in the homebuilt/experimental category. The acquisition cost would have to be competitive, which could happen if these engines get mass-produced for other applications. Durability is an issue, but since many civil light aircraft spend far less time in the air than UAVs the short time between overhaul might not be a serious limitation.
Great explanation. What a terrific teacher. The bearing problem can be solved with some kind of intermittent lubrication cycle to reduce emissions but allow the replacement of the working lubrication fluids. The compression seals can also be vastly improved with development. So, they will be great range extenders, too. I can see a removable range extender to use only when a trip of over 50 miles is needed, but for most vehicles, the 100-mile range gives a 100% greater range for anxiety reduction. Thus, a vehicle with 30% of the current battery capacity is possible. This is especially helpful for trucks where the range can vary substantially. Range extender packages can be added as needed, thus making BEVs possible by 2035. Fascinating technology.
Wow. Thank you for this amazing coverage of the Xengine. I knew their claims were too good to be true, but didn't have all the details to explain it, and you have covered it fantastically.
@@rightwingsafetysquad9872 You missed the point, they used a hollow crankshaft because it actually worked but spent too much time and money they didn't have. If Norton's had not been so expensive trying to recover costs they would have sold more and possibly kept going. Margaret Thatcher did not want ANY motorcycles on the road in Britain so refused to help (unlike reagan in USA with Harley) Major problem was Norton relied on Police contracts with bikes that were terrible for low speed escort duty, they were fast though .
Your discussion on this and similar subjects is impressively comprehensive in scope of all relevant considerations. Half way through, when I think you have covered everything, you continue with three or four more points I hadn’t thought of. And just in case you wonder, the occasional bits of levity you sometimes add, are appropriate IMO. Thank you 😎♠️🎩💙
@@jakub.anderwald No, we are not "moving" to pure EV's. We are being forced to pure EV's. If it was left to consumer choice, a plug-in hybrid would be the powertrain of choice.
@@DCBChump regardless of the reasons, we are moving. And we're not moving to EV+range extenders, just pure EV. So the need for range extenders in consumer automobiles will be probably lower over time, not grater.
@@WentzCraft Like a range extender for an electrically driven exoskeleton. Batteries + electric motors provide the torque, and this engine recharges the batteries. Last time I heard about the tech, the standard piston engine was too loud. Maybe this one can be made quiet enough?
Another problem with this engine is that it can not be stacked. If you want a bigger Wankel rotary engine, just stackmore and more rotors. With this engine, that is not really possible, as the all the intake air needs to come through one small hole in the crank.
Intake could be routed through intermediate plates, just like Wankel. Central exhaust is why they can't be stacked, because you can't put that much heat across the sealing surfaces to move it outward.
LiquidPiston themselves have claimed they can be stacked up to 3 rotors. They haven’t explained how they would do this but I’ve personally asked them and they confirmed it is possible and they hope to explore this further in the future.
This really is just a military engine. Something you didnt cover is the wide range of fuels it can run on. One might be able to-for the general public-argue it as a range extender, or a generator, but no way will it be used elsewhere without massive improvements.
I wonder if material science will ever solve the apex seal problem. I know Teflon isn't suitable for this application because of its fragility, especially under heat, but I have to imagine there's some undiscovered compound out there with similar or better friction and greater durability.
Funny you say that, driving 4 answers is misinformed as most enthusiasts not in the rotary circle are. Unbreakable apex seals have existed for the better part of 15 years now. Just google unbreakable apex seals. Theyre pricy but im 60k miles deep with no issues.
Using the exhaust port, you should be able to use the exhaust like a turbo to help inject more pressure on the fuel system. You are limited to how far you can bore out the center shaft, so increasing the air fuel mixture back pressure force is more fuel and air into the combustion chamber. This would offset the lack of blow by and make it comparable, at least with piston rings.. also, I would still use a second set of Apex seals like a Wankel to increase the compression during its firing stage
I'm not sure you have a leg to stand on with your claim of "difficult to mass produce" because this engine literally has one moving part inside of a stationary housing..versus a piston engine with how many hundreds of moving parts? The bearing and longevity issues can easily be resolved for upscale applications.
It all comes down to the manufacturing tolerances and complexity of the parts, as well as the fact that you're comparing what is essentially one cylinder to a 4 or 8 cylinder standard engine. No shit a standard v4 will have hundreds more parts, its effectively 4 times the engine. Comparing a single standard piston to this x engine, the x engine definitely looks harder to machine, instead of a simple cylinder the rotor and stator have some pretty complicated geometry going on that will require much more advanced machines, just as an example.
@@battleoid2411 However, the XEngine has the advantage of being mostly a 2D shape, so its main engine sections can be cast to near net shape using investment casting then machined to tolerance using standard 3-axis CNC machines.
That's an interesting point. Even the rebuild issue is probably minor since there's far fewer parts to even replace. OTOH that doesn't necessarily mean the rebuilds are cheaper.
I think that one of the biggest improvements both X-Engine and Wenkel engine designers can do to their engines is to accept the limitation of the seals and work on making them more serviceable. A good example of this can be seen in the typical piston engine in lawn equipment, as it's designed so that the cylinder head is accessible and simple to take apart in order to do repairs. If that kind of adjustment to design was made to the rotary engines, I'd see them being more marketable.
I think this is past the stage of quickly disappearing as they got very significant funding from the Army. Doubt it will go mainstream in the foreseeable future but for niche stuff it's definitely interesting.
@d4a - they only got funding from DoD and DARPA for drone engine research, range extenders/generators.... and they're still having the same problems they've always had... primarily sealing issues and low duty cycle. The only way to make this engine work reasonably well requires exorbitantly expensive materials.
I think it will disappear, as far as we on here are concerned. Then it'll pop up in the news in 10years, that some silent drone was shot down in Chinese airspace and we'll say..."I wonder if it has that liquid piston engine thingy in it??"
Hey thanks for an excellent video. On the issue of generators. It's not just the army. We all appreciate a light weight generator and for most of us the engine hours is not an issue. Also, the high speed means a lighter alternator.
The XTS-210 they more recently announced uses both sides of the rotor for combustion and is built as a 2-stroke, so uneven rotor heating is solved in some models.
If the German and French motor manufacturers give the politicians a hard word they’ll listen. This Carbon Zero nonsense has to end its making the western world uncompetitive, which doubtless is the intention. Getting the talking heads who know and understand little in the science and technology sectors on side is cheaper than war and just as destructive.
ICE has had a century of development. It is a highly mature technology. There is little in the way of thermodynamic gains left to be had. That is why. “It doesn’t matter what” Makes it sound that someone could come along and double efficiency. ICE is about as good as it’s ever going to get. Not going to happen, physics ALWAYS trumps marketing.
They can add pressurized oiling to the external crank bearings to improve life, add ceramic coatings to the inside, sides, and outside of combustion chamber to increase thermodynamic efficiency, and used double "apex" seals for lower blow-by. Longevity is a key issue.
Your videos stagger me!! You explain such complex information, so simply, I swear my two year old would understand most of it ! Incredible work as always
I think Atkinson cycle is possible even in traditional piston engine, without vvt. It's enough to throttle inlet, so instead of 1 ATM, the inlet gas is let's say 0.5atm. So the push stroke has a handicap in form of pressure diff between crankcase and not yet compressed mixture. And guess what... that's exactly what all gasoline (and modern diesel) engines do. Of course it gets completely screwed, when we press gas fully, because the difference is null on begin of compression stroke. Seems to me like instead of vvt purely for this purpose it is enough to leave inlet throttled. And size car vs engine in a way that power needs to drive at 120kph is possible while throttled.
Once again, an excellent, interesting and an informative description of alternative ICE design. By Showing the advantages and drawbacks of the design one can understand what type of applications it would be sutible for. Thank you.
i love how you tackle pretty much everything i wanna hear from someone talking about the liquid piston engine. i was expecting you to not include the sealing, lube and parts wear out fast like the bearing for the shaft but i was amazed when i see it has even have a special section of the video. overall wonderful vid to explain liquid piston engine and even scratch very deep on the mechanics of the wankle engine perfect/100
Really like your technically complete but very understandable coverage of this engine, and your very dispassionate reasoning about its benefits, disadvantages and areas of use. It's another example of creative minds contributing to technology diversity, and we humans must never stop that and simply concentrate all efforts on a single solution to a problem (seem familiar...?).
What always determines the viability of a new development is how friendly it is with the environment, and with the list of tasks, costs and frequency of maintenance. Everything that does not improve what exists and is proven (on the street) is teaching material for some university course.... the video is very good, very clear and specific.
Jason of Engineering Explained had a video last year talking about Mazda’s patents, among which was a potential way to control the speed of the rotating mass of the rotors by coupling their Wankel engine with an electric motor. Sort of like VTEC for rotary engines. I wonder if the hollow epitrochoid rotor could allow for a small electric motor for adjusting the rotor speeds on the go, which would reduce wear on apex seals even further. Either way, the LiquidPiston rotary engine study is long due and I’m glad you finally covered it. I really love rotary engines and I do hope LiquidPiston could commercially market standalone engines for automotive applications.
One of the main issues with the Atkinson cycle is you’re effectively using a larger engine to produce less power. It’s more efficient than a similar sized engine, but also produces less power than a similar sized engine. When you go for a smaller engine it ends up being about the same efficiency and power. Being able to switch between Atkinson and Otto can yield the best of power and efficiency depending on what you need. But, it generally ends up being overly complex for little benefit.
Thanks to this video I've learned that this engine exists, and, at the same time, that I don't need to learn more about it as a regular ar enthusiast. Thanks! :)
I just found you about a week ago and I'm LOVING your channel a TON!!!!!!!!! If I invent the next breakthrough generation of I.C.E's, I'll bring my new engine to you first for exclusive first look :P
given how difficult it is to innovate in the engine industry, kudos to this company for coming up with a new rotary design i hope they solve the drawbacks somewhat, the most glaring is the poor longevity and poor torque those bearings mean you can't put much stress on the crankshaft, so it probably is only good for constant rpm applications like generators
This is a much better explanation than any other I've seen. I have often wondered how much pollution the military produces, various aircraft being extremely inefficient but VERY high output (eg, on afterburner) and no limits set by anyone. (instead, motorists have to 'suffer' increasing legislation to compensate) In a time of war or emergency, fair enough but general use 'on a jolly'? Anyway, a supercharger and turbo would allow much smaller ports allowing side seals to be moved into outer covers, ceramic coatings less heat loss. I still see issues with rotor expansion, one side of lobes being very hot and the other (relatively) very cold. Maybe multiple intake/exhaust ports to induce extra swirl plus even out massive temperature gradient? As diesels are direct injection, very high boost pressure can be used for scavenging, fuel being injected as usual during the burn cycle should allow a reasonably high rpm. I would think it won't be a problem to fit inboard oil seals to main bearings then use pressure fed mains at least, reducing cost and weight even at expense of adding oil pump and reservoir? Using 'specified' (two stroke) oil would allow a bleed off to lubricate internal gears. Service interval would consist of changing spark plugs and topping up oil.
Suggestion for future videos: Why timing chain guides, made of plastic, keep failing, even in best cars (BMW, Maserati, Bentley) and what could be done to prevent it. Suggestion no.2: what are the most reliable modern BMW engines (e... da poludi čovek u Americi, nema šta da se odabere, a da nije Toyota). Suggestion 3: sad story about self-destructing electric water pumps. Top 5 reliable engines making about 300 hp, 400 hp, 500 hp... Svako dobro i pozdrav i Hjustona
Thanks. I first thought "20 minutes on some new miracle engine?!?!?! You gotta be kidding me!" But figured what the heck, give it a couple of minutes, and next thing I know, you're wrapping it up and I've learned a lot and wondering "Hey! You promised 20 minutes!" and lo and behold, it WAS 20 minutes. Really really good presentation.
another benefit of the Wankel is that you can stack as many rotors as you want. the design of the Liquid Piston doesn't lend itself to be able to run multiple rotors.
I was glad yo see you have a look at this. Ive seen enough thumb nails on youtube i knew it was out there, but didnt think most of them would look at the realistic failings of a unique design. I write this as an old mazda rotary fanboy, sitting in my living room next to the 12a rotor thats an ornament. I appreciate different, weird, obscure, abd overall creative engine designs, being fully aware that so many of them are flawed. I think of them more like art, i appreciate it for the creativity, the design and engineering, but comfortable with them being ultimately kinda useless.
Fascinating, as usual! Always brain food here even for my tired and slow 73 year used cranium. Ah to be young and snappy again. Regardless, a real blast hearing from a real engineer (as fast as this non-engineer can tell ...LOL). Thx again.
I’m a big fan of rotary engines and the Liquid Piston engine intrigues me for being a clever way of putting the Atkinson cycle into practice but I agree with you, it still needs improvements to become something that is universally better than the piston engine.
At least i see that it's inherently better and certainly the design can be improved a lot. Unlike wankel👍
Hey man! A big thank you for watching and dropping by 👍👍 Watched many of your jet engine related vids and loved them!
It looks like a very promising design for the dirt bike industry, as longevity is a much smaller consideration. Many riders rebuild their engines after much less than 1000 hours, especially racing.
The power density, low weight, and relatively simple construction would be very convenient in a high performance engine for dirt bikes. And rebuild/overhaul may be easier due to the fewer parts.
Plus, they sound amazing which tends to be popular in motorsports.
Admittedly, the low torque could be detrimental, but gearing would likely be enough to compensate for that in such a light weight application as dirt bikes.
@@prabowomantoro3945 Inherently better apart from not being able to lube the crank.
Thats a bigger drawback than an elephants fore***n.
The potential does seem there though, and it has more use cases still
Was optimistic about this engine for a while, but just like Achates Power, they unfortunately seem to have become one of the countless entities that promised to "change everything" but ultimately delivered little or nothing.
I agree. Knowing that d4a is a self taught RUclipsr makes me look at things like this now differently. This one and the one cycle motor are not realistic for most people if they ever come for sale.
Just because an product/idea goes nowhere, has nothing to do with the value of the idea.
I mean I think you have to consider a bit broader view of these things.
Any new engine has to compete with the already existing units that have absolutely insane amounts of cumulative development spending behind them.
So already from the get go it's super hard to be competitive. However many of these concepts such as for example the Achates double piston engine should be able to be competitive. The issue is just that due to all that EV nonsense it's totally uninteresting, unhip and also not supported by the state to invest into anything like this.
If you ask me, we first need a resurgence of appreciation for combustion engines to set the plane to actually get people to build and invest into these new concepts.
I agree. All I see of this engine are adds seeking investment money. Same for that Aptiva solar EV car. The production date is always a year away.
And this engine is no different. Pipe dream..
I very much appreciate how you talk about both the ups and downs, instead of focusing on one or the other. Whenever I hear of a new engine technology, I'm always excited to hear your views on it because of your balanced and fair analysis.
I second that. Way too many YT channels just excitedly repeat all the nice things a company's press releases say about their new product (that needs funding and buyers), with absolutely zero critical analysis.
Finally, an analysis of this engine that doesn’t feel like paid marketing, nor is a video just crapping all over it because it’s different. It was great to see someone actually gather all the numbers together and go through them in a comprehensive video.
I’ve followed this engine for a while and knew something had to be up with the engine for LPI to have been stuck in ‘development’ for so long. Thanks for pointing out the longevity and efficiency figures as well as the most glaring weakness in the crankshaft.
This dude shilled for many other products, this is just one that he bothered to actually look at.
@@a-iz4pg I usually criticize video's pretty severely but you seem to be making unfounded comments?
D4A has been overenthusiastic a few times ( which I have commented on) but pretty sure he's not a shill.
@@1crazypj Except for all those times he was which kills credibility.
@a-iz4pg Name them please. Some of us might want to look and make our own opinions.
@@ChevyConQueso I was wondering the same thing but didn't want to look like a 'fanboy' 😄
This channel is so important. No shilling. Just factual observation and simple technical translation in a consistent manner with no fluff.
Great tear down and analyses of these engines. Just love clear language and no annoying back ground audio. Thanks, 5 Stars.
One added benefit over the Wankel engine that I don't think you addressed is that it heats up more evenly. One of the problems with the Wankel is that it only fires on one side and will shift and deform because of that.
Don't know if it's a realy problem, but that x-engine is inverted Wankel engine, so only one side of a piston is opposed to combustion stroke and is heated more than another.
@MaximusU76 - even though only one portion internal rotor face is a "combustion surface", the rotor functions as an intake runner, which facilitates a considerably more uniform temperatures. Also, diesels bleed off about half the surface temperature per kw/hr load because they're more thermally efficient.
@@driverjamescopeland Maybe.
except that the rotor has a hot side and a cold side
The heat distribution problem is inverted:
A Wankel has even heat distribution around the rotor (because all faces go through the same cycle) but uneven distribution around the housing (which has distinct areas for each phase of the cycle).
The X-engine has even heat distribution around the housing (because each of the three chambers goes through the same cycle) but uneven distribution around the rotor (which has distinct ends for intake-exhaust and the for compression-power).
I think it's my standard comment at your vids: 'When I think I know it all, something clever and new comes up." How interesting and what a clear explanation again. Thanks!
The diesel may be better in a uav due to higher efficiency resulting in longer loiter time, and not having to shield electrical noise from the ignition system.
Hmmm true, good point
There are still injector coils. I'm not aware of any purely mechanical diesel injection system that can keep up with target RPM for this engine.
the diesel version should be able to run on road diesel and jet A. The military isn't going to want to carry around a few jerry cans of pump gas just for this
But compression ignition with diesel means you get loud diesel clatter and smoke. You have to remember, this engine still needs to burn 2T oil for apex seals like a conventional rotary. The enemy will see you from a mile away because of the smoke trail . Maybe UAV with this engine can be used to spray pesticide for agricultural use, or maybe mosquito fogging , but not stealthy enough for military use.
Are non-ignition engines safe from EMP attacks? @@d4a
This does sound very useful for military applications. Definitely very compact, and if it is quieter, that’s also a nice bonus. On the logistical side of it, you can ship a bunch of them out, and pick up the broken ones at the same time, and you’d just need one state-side facility to take in all the spent engines & rebuild them & put them back in circulation.
Maybe also could be useful for camping or wilderness trips since it is so small & light, but the reliability becomes an issue then.
Very interesting little engine.
I already mentioned this in few videos. In Finland moped is defined as no more than 50cc and around 5hp well as cant move faster than 45km/h. Since we have engine size limit and changing gear ratio's make first gear ridiculously slow with high torque and make engine in 5th gear scream, or 1st being with out torque and 5th gear being reasonable, low capacity max50cc, high torque diesel would be ideal and its easy to limit mentioned speed, but with ability to torque trough steep hills and have cheaper fuel source, but there havent been any diesel engines compact enough to retrofit into older moped that dont have emission bullshit. Witch only dirty the engine and eat power. Despite what he said, emissions are not a issue, least when retrofitting engine to older moped and who wants the modern plastic trash anyways? Two strokes need rebuilding time to time and kids tuning them up with out knowing what they are doing, so rebuilding them aint problem ether. Long as engine is light weight diesel with more torque than same size 2 or 4 stroke engine, that can last same as two stroke, easy to fix and rebuild and cheap to purchase, it would be hit. Too bad they are not yet selling them anywhere.
Wankel would be another nice engine, but there too you cant find 50cc ones and even then the larger ones are hella expensive regardless of condition.
I'm into paramotoring, ultralight form of aviation where we carry the motor in our back. What we want: absolute most power out of least amount of mass and space. Also, as we have "a lawnmower" in attached in our backs, it is nice if it does not vibrate that much. The drawbacks of the liquid piston would not be problems in this sport:
- *Longevity:* Our current two stroke engines last ~300h anyways before full rebuild. Something like 1000h would be a dream
- *Torque:* Propeller does not need it
- *Difficult to mass produce:* Our current motors are hand crafted and expensive anyways.
- *Poor emissions:* Haha lol, not on list of priorities :D. The paramotor is practically a large fan that blows the fumes away from self anyways
As nice as it would be I bet their described weight doubles at minimum once a clutch, battery, reduction drive and cooling system are added
Also, this thing can burn many different fuels.
It can be made to burn anything from hydrogen to diesel.
Of course it'll have different performance characteristics depending on the fuel.
So UAVs _and_ paramotoring. So I guess the takeaway is that this engine would work for:
- Flying vehicles without people
- Flying people without vehicles
@@PSUQDPICHQIEIWC 😂😂😂
Thank you for a very level-headed breakfown of something that the media tends to oversell.
Really love the work and the good engineering approach to these subjects.
This channel has taught me a lot, I am proud of the fact that when they said the crankshaft supplied the air mixure my first thought was "that's not gonna mix well with lubrication".
This dude is an awesome teacher.
Truthful and to the point.
Always enjoy your videos.
Thank you.
As always, spot on. Great explanation. I am a mech designer, with some hobby affinity with engines. For my dad it was his life. He would have enjoyed this a lot!
It is an art in itself to explain complicated things simply. You 've got it!
First time I've listen to one of your videos and I must say that I am impressed by the in depth coverage as well as the pros/cons presentation.
This is the best video I've seen yet on the X-Engine, bravo!
I was not aware that they were trying to shove air through the crankshaft, I had just assumed there was a divider in the center of the rotor so they could push air in one side and let exhaust out the other. That seems like something they're going to need to fix before they can make much progress on commercialization.
I understand the amount of rotor surface area that's exposed to combustion poses a big heat management problem and makes it challenging to turbocharge. Of course if you could turbocharge one of these then the power/weight would be up into the turbine realm and even 30% efficiency would be a huge win for aviation.
They already have a turbo charged 2-cycle, the XTS-210.
Good idea using a divider in the rotor center
Extremely interesting concept and I believe you have accurately predicted its future. As always the speed, clarity and accuracy of your presentation is superb. The text of your presentation caps it off, allowing time to absorb the subject in depth. Many thanks.
This the most comprehensive and realistic explanation of this engine. In the end, the same core defficiencies will doom it to the wankel’s fate. At this point, it is diificult for any “new” internal combustion design to out perform existing ic technology that has the benefit of over 100 years of progress.
Is the last truly unique mass market combustion engine, the gas turbine?
@@Appletank8 probably, but the discussion here is about car engines. Turbines were tried in the 50’s and 60’s and didn’t work out for land vehicles. They definitely would not meet emission standards now even if the other problems were worked out.
@Appletank8 it kinda maps the same as warships, they went from steam piston engines to steam turbines, aircraft too went from gasoline piston engines to gasoline turbine engines. I feel like pistonless engines other than turbines are just re inventing the wheel by putting feet at the end of spokes...
Nah man you can do anything with US military funding 😎
@@Appletank8 microturbines are gaining interest again, and for good reason. Turboshaft engines can be tremendously efficient and incredibly power dense, but making a muffler for them is damn near impossible. Some guy put a boeing turboshaft in a Miata and gets like 70MPG with it, but it sounds exactly like you'd expect a Miata sized Boeing to sound like.
For the (sealed) Crankshaft Support Bearings, you would hope that these Bearings have been filled with High Temperature Grease - when operating at those temperatures. The 'normal' grease in many bearings would simply 'run-out' very quickly, leaving little or no lubrication. Mind-Blowing how this guy can study all engines in complete depth, and even their shortcomings in design. I'd like to know what car he drives.....because it has probably got the best-designed Engine!! Greetings from Australia
It would need oil- circulating oil which lubes and cools bearings and other super important parts
❤ MR2
The problem is less lubrication and more heat build up. Using sealed bearings and with no cooling available there is nothing to cool the surfaces so there is no way to control heat. That means either massive tolerances - which leads to massive wear and innefficiency - or as it seems here a need for replacement every 1000(!) hours which in reality would be a lot sooner especially if it was heat cycled often as most car engines are a couple of times per day.
I don't see why forced oil lubrication / cooling couldn't be used with this design via using 2 oil seals per side and using a feed and outlet port from the housing into / out the bearing?
@@Samqdf Have a think about the complexity and amount of sealing pieces it would rely heavily on. Then remember we're talking about mass production tolerances.
The failure rate would be through the roof.
I always wonder instead of a passive apex seal, couldn't you use a piezoeletric actuator to maintain seal without lubrication. Given in regular piston engine, the gap between cylinder and ring is around 50 microns. A typical piezo actuator has travel length around 100 microns with resolution around 0.5-1.5 nanometer and response time around few microseconds. So you could have a active apex seal that continuously monitor the distance between rotor and stator and maintain a few nanometer gap without lubrication, thousands of times per second (0.5-5 response time, so about 1mhz position update frequency). In an active seal system, it also solve another issue where uneven heating of the engine chamber create larger gap, since the actuator seal will just compensate for thermal expansion and increase the travel distance. Piezo actuator is pretty cheap too, around 4-5 bucks each. So cost shouldn't be too expensive.
Modern HDD hard drive use such piezo electric actuator at its magnetic reader head to maintain the nanometer gap above hard disk. The reader head actuator can move at insane speed with equally insane acceleration while compensating for thermal expansion of the disk time in real time. And it's done at a commoditized price tag. Similar piezo actuator technology should be able to transfer to apex sealing environment to maintain a way smaller gap and needing much less or no oil. Since the tolerance for a hdd drive gap is way smaller than a piston ring gap.
now add wires.
add heat.
do it 200 times a second.
sensors. connections. interfaces. software. hardware.
this was apex seals right? mounted in a rotor? that spins on bearings? and then spins on an eccentric that also spins?
keep wondering ;)
This seems possible, PZT (Lead Zirconium Titanite) which is most common, has high temp resistance. Especially if the actuator in question worked in conjuction with a simple analogue circuit.
@@paradiselost9946 Well, remember the X engine (stupid name lmao) operates with fixed apex seals, and not rotor-mounted apex seals. So the wiring could go to a remote module and the piezo actuator itself would be housed in the block, not the rotor.
dont hdds hate shocks and vibrations tho?
Thank you for the well prepared video ! Big kudos for having also very committed community who are willing to watch 20 minutes with enthusiasm and a lot of comments 😊
Thank You! In my opinion you have the Best explanations of engine tech in a way that the average person can understand! Detailed, accurate, reliable info! I rate you #1 on RUclips!!!
Incredible video. I know nothing about ICE’s, other than their general theoretical function, but I accidentally stumbled upon one of your videos some months back (🤔 Scotch yoke engine!), and I’ve been hooked. Your explanation and analysis is thorough, concise, well-explained and totally fascinating. Just a winner of a channel. Outstanding work, thank you.
This motor… could it be deployed in a motorcycle…😳 …maybe a diesel bike
Thank you so much for the kind words. Motorcycles are also subject to stringent emissions nowadays in most markets so I doubt chances are high. Plus, current engines are simply very good. You have small and lightweight parallel twins delivering everything anyone could ask for.
@@d4a🤣 Of course, I paused the video to type the comment… and as usual, you are covering it all very thoroughly. As a biker, I can say you’re spot on- he parallel twins today have been able to be efficient, strong, slim and light, and the vibration balanced out enough to be so versatile. Hondas are particularly good; I had a new CB500F, and plan on buying an Africa Twin, and both are fantastic. The V is still the “ideal” for a bike, though… for feel and character. I had a couple of Italian Aprilia bikes that were just a joy to ride for the feel… Thanks again!
The military has been trying to get diesel motorcycles in their fleet for years, the idea being that they only need to have one fuel for all applications. Kawasaki KLR Diesel was the closest they came. Enfield of India tried it too for a while, and as pointed out, the military doesn't care about emissions, so it could be a possibility in the future.
Liquid Piston is actually focusing on investors just like yourself on Facebook. People who are not very knowledgeable about this subject. So I wonder if the technology was so wonderful wouldn’t they look for investors who are knowledgeable about this category of technology?
@@somenygaard If your insane enough to research a new IC engine technology, you take investors wherever you can find them, and Facebook is full of idiots. The US military answers your question, it's a perfect fit for the Xengine, and they aren't idiots.
Xengine? I wonder if they were looking to Musk to invest, if so they are idiots.
You always have so many things right, never mind about the outro being a bit wrong! Thanks for your crystal clear explanation!
One thing I remember hearing about the Wankel is that because insurance is/was calculated based on displacement, there was some disagreement about displacement definition on a Wankel. One side argued it was the entire chamber, the other side argued that it was only the third that did the combustion. The former side won, so the insurance was WAY too high for the fun factor and it turned people off.
With the geometrical inversion of this design, that displacement definition matches the power scaling and would assuage that.
I was waiting for the seal and emission problems to come up. Thank you for the great explanation.
I already have an engine design that does all the stuff this does even better with a lot less parts. I'm still working on the emissions issues, but it should be exceptionally good on that regard as well. This concept is interesting though. This channel always provides some good new things to learn.
I love watching your videos. Your way to explain complicated things with all the graphics is just awesomme. It helped me a lot. Thank you!
Looks like a good candidate for the air compressor head - quiet and with good heat dissipation, also no issues with injecting oil. Would stand somewhere between piston and scroll compressors.
i think that place is already taken by some other semi thorid engine. also this one would have problems with oil
Always impressed by the thoroughness and clarity of your narration - and the animations - just incredibly awesome work.
A lot of motorcycles use ball bearing cranks granted they usually are not sealed. I think it would be perfect for a bike and if the bearing is easier to replace I would take that tradeoff. My dirtbikes require rebuilds a lot more frequently than you'd think.
I also think diesel being used as the primary fuel would also allow the side seals and apex seals to last a lot longer than gasoline because diesel is a lubricant.
Unbreakable apex seals have been a thing for nearly 15 years. Driving 4 answers is just misinformed.
@@caboose22320 the issue is less about apex seals breaking and more how reliably they actually seal the chambers off from each other, and lubrication issues. The Wankel has a problem in that the ignition port will almost always leak some air through, and the side seals still aren't as good as piston seals.
@@Appletank8 this is it... a piston ring just oscillates, and only "seals" during combustion when its forced down and out.
an apex seal is getting hit with intake vacuum on one side, combustion on the other, or combustion, exhaust, or whatever... never a constant predictable force but a constant change from tilting one way to tilting the other... same nasty approach angle with teh wall of the trochoid itself... side seals have massive sliding frictions, and again, nothing in a rotor has that simplicity of a piston ring being ASSISTED by combustion pressure to seal...
i say it again. the only TRUE "liquid piston" is a humphrey gas pump. dont need rings or bearings when the piston is water!
The amount information that this guy communicates in a clear and understandable way is just amazing. If my engineering professors could have communicated as well as this dude, I would have graduated in two years rather than four. This dude should be a politician, he could "enlighten" the masses who require enlightening.
never expect peanut shaped piston will as good as this before.
Thank you for being realistic and thorough about these things, instead of just parroting the hype to get views.
I was deeply concerned about that hollow crank shaft before lubrication issues were discussed! That has got to be the most restrictive and problematic path for intake air to travel that has ever been imagined!
That's my concern as well, especially when used in a diesel configuration!
Whilst true there is technically the potentiol to build it with lubrication in there, it will just result in a crankshaft thats larger for the engine output, but i don't think thats an issue here honestly.
rather than the lubrification i'm more concerned about the air temperature the very moment it crosses inside the crankshaft considering it passes side by side with the exhaust gasses and enters a high-temperature nest.
@@Quartolone This is an issue they acknowledged somwhere else when discussing it. Apparently makes it impractical to turbocharge.
@@Quartolone Good point!
I saw this engine many years ago and thinked why it didn't reach the consumer market. Thanks for you great explanation!
Thank you so much for making this. If this, and other new engine designs do nothing else, they do show that human ingenuity and inventiveness has not yet stopped, also with the 'improvements' to conventional internal combustion engines. Interesting times!
A very compelling case, well argued and explained about what works, and what doesn't.
Too many sliding surfaces poorly lubricated for me.
So that's not a dorito, it's a... peanut?
Superb video as usual, had no idea these were a thing!
Ive looked at just about every other sites descriptions of this intriguing engine. Yours is by far the best, including the logic of the 'liquid' piston, which I looked everywhere for the reason for it. Thanks
The crankshaft bearing problem (if you can call it a problem) can easily be solved by moving the intake system from the crank to a port on the opposite side of the engine where the exhaust is located and adapting the rotor with a slant port. It may even generate a vortex to mix air/fuel better.
45% thermal efficiency might be pretty nice if it also comes with a weight, complexity, and wear reduction. I also wonder how the gas version would handle a turbo.
Or perhaps they could take advantage of the increased surface area that's exposed to the combustion process by having an oversized cooling system, use this engine as an EV range extender, then add a Stirling Engine to extract electricity out of that heat, dump it directly into the charge controller, potentially boosting the engine's thermal efficiency considerably.
THe big thing I can see it working for is in an every day Diesel motorcycle. It's decent power output in a very compact size really sells itself as a possible new engine for a line of motorcycles. A new brand of affordable, older tech parts with a fairly robust, spunky diesel engine for those efficiency gains could do wonders. Also, 40-50 horsepower isn't high in the realms of bikes, but is more than useable. I also expect that number to rise as they possibly size the engine package up. Being 11 inch by 11 inch currently it's still on the small side, and upping to a larger package could help on the power front, and being a rotary helps size down the attached components on the bike.
Being able to reduce the extra space required to house the crank shafts, cams and other upper and lower accessories shortens the height, freeing up room for a larger tank, or even room for a small battery bank. Possible (though highly skeptical if it would ever be properly explored) Diesel Electric Bike.
Also assuming it has a similar torque curve to most rotaries, and that the compression benefit of a diesel would push peak torque down a bit I would feel comfortable putting peak torque at 3750-5250 rpm. Rotaries are much less peaky with their torque, having very gentle torque falloff up until you hit peak power where it starts to TANK (Peak power is at where torque tanks BECAUSE the torque tanks at that rpm). Would make for a very easy to learn on engine that has consistent pull from peak torque to the redline. Based on peak power torque of 37 ft-lbs I would put peak torque probably at 43-47 ft-lbs (Unsure how the Fuel, Flame propagation and compression ratio would affect how far higher peak torque is to torque at peak power. IIRC Other rotaries are fairly consistent, with the RX8 being something like ~160lbs at 5500 and ~153 lbs at 8500)
I also see the option with the extra space available vs a piston alternative to introduce a Supercharger/Turbo, further granting it an advantage over piston bike engines who forgo the option commercially most of the time due to space/design constraints, a lack of need (most engines above 500cc are MORE than capable enough) and a cost cutting measure. Also, turbo bikes are just much less rider friendly, as the turbo lag is much more deadly a consideration. Given that a 50hp 750cc engine is quite underpowered vs most high rpm 750 pistons easily breach 100hp or more, they are larger in package size. I could see a small supercharger on the x4, especially if they can add another rotar to it getting into the 85-100hp range at a very respectable around town rpm range.
This is all just speculation at this point, but I REALLY like the possibility of a respectable diesel option in the motorcycle market, Netting us a VERY fuel economical option with VERY long range due to a larger tank and less consumption per mile, while having a much easier time accessing fuel due to the abundance of different fuel types you could plug into the engine. Imagine if your motorcycle got 100MPG(2.35l per 100km) or more, and you could create your own fuel with foodscraps, waste oil or other sources. Not a benefit in the city, but with the size of rural USA, having a biofuel option to help fund going into town for some fun, or just smaller shopping trips sounds like an amazing option to have available. Would cost a premium though as I don't see a diesel bike being popular if it doesn't net at least 80% power of a comparable motorcycle size, due to the FUN factor a large quantity of people buy them for.
really very well explained, good job, keep it up!!!!!!!!
Well you're the first one that pointed out the shortcomings I have been talking about ever since I've seen the design - emmission due to lubrication and longevity due to seal type. I even talked about it in class (I am an automotive teacher in Celje). And you explained so much more!
If this engine turns out to be suitable for UAVs it might also be suitable for light aircraft, at least in the homebuilt/experimental category. The acquisition cost would have to be competitive, which could happen if these engines get mass-produced for other applications. Durability is an issue, but since many civil light aircraft spend far less time in the air than UAVs the short time between overhaul might not be a serious limitation.
You, sir, are a marvelous teacher. You also have some of the best teaching aid animations I have seen anywhere. Thank you for all you do! Subscribed!
I wonder if these could work as superchargers, and how well they could work as such.
Interesting point. Longer axis, and add two ports to the eccentric shaft... I'd like to see how it performs as well.
no well i guess... wankel can work as one but its bigger than actual engine
Well wankels where originally made to supercharge air.
As a aircondition pump.
A mix of a vane pump and a ring pump basicly
Great explanation. What a terrific teacher.
The bearing problem can be solved with some kind of intermittent lubrication cycle to reduce emissions but allow the replacement of the working lubrication fluids. The compression seals can also be vastly improved with development. So, they will be great range extenders, too. I can see a removable range extender to use only when a trip of over 50 miles is needed, but for most vehicles, the 100-mile range gives a 100% greater range for anxiety reduction. Thus, a vehicle with 30% of the current battery capacity is possible. This is especially helpful for trucks where the range can vary substantially. Range extender packages can be added as needed, thus making BEVs possible by 2035. Fascinating technology.
If only this had been invented instead of the Wankel, it would have had enough dev time to actually be useful.
Wow. Thank you for this amazing coverage of the Xengine. I knew their claims were too good to be true, but didn't have all the details to explain it, and you have covered it fantastically.
“So what I need you to do is machine a hollow crankshaft so I can use it as an intake”
*machine shop door slams
Norton did it with their Wankel engine in the 1980's, nothing new
@@1crazypj How’s Norton doing today though? Just because something can be done, doesn’t mean it’s good for business.
@@rightwingsafetysquad9872 You missed the point, they used a hollow crankshaft because it actually worked but spent too much time and money they didn't have.
If Norton's had not been so expensive trying to recover costs they would have sold more and possibly kept going.
Margaret Thatcher did not want ANY motorcycles on the road in Britain so refused to help (unlike reagan in USA with Harley)
Major problem was Norton relied on Police contracts with bikes that were terrible for low speed escort duty, they were fast though .
@@1crazypj That was exactly my point. I didn't miss anything. I just used fewer words to say it than you did.
Your discussion on this and similar subjects is impressively comprehensive in scope of all relevant considerations. Half way through, when I think you have covered everything, you continue with three or four more points I hadn’t thought of. And just in case you wonder, the occasional bits of levity you sometimes add, are appropriate IMO. Thank you 😎♠️🎩💙
I think a range extender would be a beautiful application for this.
Yes. However, the rang eextenders' market is dwindling, we're moving to pure EVs.
@@jakub.anderwald Absolutely! but there could be some niche remote or military applications.
@@jakub.anderwald
No, we are not "moving" to pure EV's.
We are being forced to pure EV's.
If it was left to consumer choice, a plug-in hybrid would be the powertrain of choice.
@@DCBChump regardless of the reasons, we are moving. And we're not moving to EV+range extenders, just pure EV. So the need for range extenders in consumer automobiles will be probably lower over time, not grater.
@@WentzCraft Like a range extender for an electrically driven exoskeleton. Batteries + electric motors provide the torque, and this engine recharges the batteries. Last time I heard about the tech, the standard piston engine was too loud. Maybe this one can be made quiet enough?
My first tjought was hey they turned the rotor into a block and made the block into a rotor. Well done as usual!
Another problem with this engine is that it can not be stacked. If you want a bigger Wankel rotary engine, just stackmore and more rotors. With this engine, that is not really possible, as the all the intake air needs to come through one small hole in the crank.
Intake could be routed through intermediate plates, just like Wankel. Central exhaust is why they can't be stacked, because you can't put that much heat across the sealing surfaces to move it outward.
LiquidPiston themselves have claimed they can be stacked up to 3 rotors. They haven’t explained how they would do this but I’ve personally asked them and they confirmed it is possible and they hope to explore this further in the future.
They said we would never put a man on Mars
no i think you can stack them just fine. stack 2 rotors and each one gets air from one direction
I quite agree on this: two is the practical maximum.
Thank you once more for analyzing the thing better than anybody else here.
This really is just a military engine. Something you didnt cover is the wide range of fuels it can run on. One might be able to-for the general public-argue it as a range extender, or a generator, but no way will it be used elsewhere without massive improvements.
suddenly all kinds of engines pop up from anywhere. can't be that beautiful
I wonder if material science will ever solve the apex seal problem. I know Teflon isn't suitable for this application because of its fragility, especially under heat, but I have to imagine there's some undiscovered compound out there with similar or better friction and greater durability.
Ethically sourced Siamese cat whiskers. Material of the future.
@@MattyEnglandSure
Funny you say that, driving 4 answers is misinformed as most enthusiasts not in the rotary circle are. Unbreakable apex seals have existed for the better part of 15 years now. Just google unbreakable apex seals. Theyre pricy but im 60k miles deep with no issues.
@MrDowntemp0 Recent discoveries of Moon minerals that are plentiful may be a longer term solution.
Using the exhaust port, you should be able to use the exhaust like a turbo to help inject more pressure on the fuel system. You are limited to how far you can bore out the center shaft, so increasing the air fuel mixture back pressure force is more fuel and air into the combustion chamber. This would offset the lack of blow by and make it comparable, at least with piston rings.. also, I would still use a second set of Apex seals like a Wankel to increase the compression during its firing stage
I'm not sure you have a leg to stand on with your claim of "difficult to mass produce" because this engine literally has one moving part inside of a stationary housing..versus a piston engine with how many hundreds of moving parts? The bearing and longevity issues can easily be resolved for upscale applications.
It all comes down to the manufacturing tolerances and complexity of the parts, as well as the fact that you're comparing what is essentially one cylinder to a 4 or 8 cylinder standard engine. No shit a standard v4 will have hundreds more parts, its effectively 4 times the engine. Comparing a single standard piston to this x engine, the x engine definitely looks harder to machine, instead of a simple cylinder the rotor and stator have some pretty complicated geometry going on that will require much more advanced machines, just as an example.
@@battleoid2411 However, the XEngine has the advantage of being mostly a 2D shape, so its main engine sections can be cast to near net shape using investment casting then machined to tolerance using standard 3-axis CNC machines.
That's an interesting point. Even the rebuild issue is probably minor since there's far fewer parts to even replace.
OTOH that doesn't necessarily mean the rebuilds are cheaper.
I think that one of the biggest improvements both X-Engine and Wenkel engine designers can do to their engines is to accept the limitation of the seals and work on making them more serviceable. A good example of this can be seen in the typical piston engine in lawn equipment, as it's designed so that the cylinder head is accessible and simple to take apart in order to do repairs. If that kind of adjustment to design was made to the rotary engines, I'd see them being more marketable.
That longevity issue is a killer but it is amazing that it can work with diesel
Diesel is a big positive, apart from anything else it's a lubricate.
Such a well produced doctorial by such an amazing engineer with his fabulous command of language! So well done!
Now, what would happen if those engines becomes hybrid? Sounds like a new engine is brewing.
I come from 7 months later and I can confirm nothing brewed
@@manuelventura3799 yep, still nothing
Probably the 1st video about liquid piston engine which doesn't look like a commercial. It makes me to subscribe for this channel.
They will hype this as much as possible, Then it will disappear 🤣
I think this is past the stage of quickly disappearing as they got very significant funding from the Army. Doubt it will go mainstream in the foreseeable future but for niche stuff it's definitely interesting.
@d4a - they only got funding from DoD and DARPA for drone engine research, range extenders/generators.... and they're still having the same problems they've always had... primarily sealing issues and low duty cycle. The only way to make this engine work reasonably well requires exorbitantly expensive materials.
That unfortunately seems to be the ongoing theme. The delta design opposed piston shown several years in an F-150 seems to have disappeared
I think it will disappear, as far as we on here are concerned. Then it'll pop up in the news in 10years, that some silent drone was shot down in Chinese airspace and we'll say..."I wonder if it has that liquid piston engine thingy in it??"
@@davidjernigan8161 - to be fair... doesn't Cummins offer the opposed piston diesel for some applications in unregulated countries?
Hey thanks for an excellent video. On the issue of generators. It's not just the army. We all appreciate a light weight generator and for most of us the engine hours is not an issue. Also, the high speed means a lighter alternator.
As a former U.S. Army mechanic I can confirm the Army doesn’t care about engine longevity, or if half the fleet even works 😂
The XTS-210 they more recently announced uses both sides of the rotor for combustion and is built as a 2-stroke, so uneven rotor heating is solved in some models.
It doesn't matter how good it might be. EU lawmakers will never allow any ICE engine to challenge the religion of electric cars from now on.
Indeed 😅
If the German and French motor manufacturers give the politicians a hard word they’ll listen. This Carbon Zero nonsense has to end its making the western world uncompetitive, which doubtless is the intention. Getting the talking heads who know and understand little in the science and technology sectors on side is cheaper than war and just as destructive.
ICE has had a century of development. It is a highly mature technology. There is little in the way of thermodynamic gains left to be had. That is why.
“It doesn’t matter what” Makes it sound that someone could come along and double efficiency. ICE is about as good as it’s ever going to get.
Not going to happen, physics ALWAYS trumps marketing.
EU is ZSRR-bis and will collapse the same way. It's only a matter of time.
They can add pressurized oiling to the external crank bearings to improve life, add ceramic coatings to the inside, sides, and outside of combustion chamber to increase thermodynamic efficiency, and used double "apex" seals for lower blow-by. Longevity is a key issue.
Wasn't the rotary a complete disaster? 😂
Yes but braap
No
Your videos stagger me!! You explain such complex information, so simply, I swear my two year old would understand most of it ! Incredible work as always
Yeah, he’s really good at explaining things that we can understand, I wonder what he’s day job is, lecture/teaching?
I think Atkinson cycle is possible even in traditional piston engine, without vvt. It's enough to throttle inlet, so instead of 1 ATM, the inlet gas is let's say 0.5atm. So the push stroke has a handicap in form of pressure diff between crankcase and not yet compressed mixture. And guess what... that's exactly what all gasoline (and modern diesel) engines do. Of course it gets completely screwed, when we press gas fully, because the difference is null on begin of compression stroke. Seems to me like instead of vvt purely for this purpose it is enough to leave inlet throttled. And size car vs engine in a way that power needs to drive at 120kph is possible while throttled.
Once again, an excellent, interesting and an informative description of alternative ICE design. By Showing the advantages and drawbacks of the design one can understand what type of applications it would be sutible for. Thank you.
i love how you tackle pretty much everything i wanna hear from someone talking about the liquid piston engine. i was expecting you to not include the sealing, lube and parts wear out fast like the bearing for the shaft but i was amazed when i see it has even have a special section of the video. overall wonderful vid to explain liquid piston engine and even scratch very deep on the mechanics of the wankle engine
perfect/100
Really like your technically complete but very understandable coverage of this engine, and your very dispassionate reasoning about its benefits, disadvantages and areas of use. It's another example of creative minds contributing to technology diversity, and we humans must never stop that and simply concentrate all efforts on a single solution to a problem (seem familiar...?).
What always determines the viability of a new development is how friendly it is with the environment, and with the list of tasks, costs and frequency of maintenance. Everything that does not improve what exists and is proven (on the street) is teaching material for some university course.... the video is very good, very clear and specific.
Jason of Engineering Explained had a video last year talking about Mazda’s patents, among which was a potential way to control the speed of the rotating mass of the rotors by coupling their Wankel engine with an electric motor. Sort of like VTEC for rotary engines. I wonder if the hollow epitrochoid rotor could allow for a small electric motor for adjusting the rotor speeds on the go, which would reduce wear on apex seals even further.
Either way, the LiquidPiston rotary engine study is long due and I’m glad you finally covered it. I really love rotary engines and I do hope LiquidPiston could commercially market standalone engines for automotive applications.
One of the main issues with the Atkinson cycle is you’re effectively using a larger engine to produce less power. It’s more efficient than a similar sized engine, but also produces less power than a similar sized engine. When you go for a smaller engine it ends up being about the same efficiency and power.
Being able to switch between Atkinson and Otto can yield the best of power and efficiency depending on what you need. But, it generally ends up being overly complex for little benefit.
Thanks to this video I've learned that this engine exists, and, at the same time, that I don't need to learn more about it as a regular ar enthusiast. Thanks! :)
Every time I watch one of your videos I feel smarter. Thank you!
I can also see it as a good auxiliary engine for gliders.
No need for huge power, but saving on the mass of the engine and less fuel has its benefits.
I waited for you so long to do this video, finally made it congrats man!
I just found you about a week ago and I'm LOVING your channel a TON!!!!!!!!! If I invent the next breakthrough generation of I.C.E's, I'll bring my new engine to you first for exclusive first look :P
given how difficult it is to innovate in the engine industry, kudos to this company for coming up with a new rotary design
i hope they solve the drawbacks somewhat, the most glaring is the poor longevity and poor torque
those bearings mean you can't put much stress on the crankshaft, so it probably is only good for constant rpm applications like generators
This is a much better explanation than any other I've seen.
I have often wondered how much pollution the military produces, various aircraft being extremely inefficient but VERY high output (eg, on afterburner) and no limits set by anyone. (instead, motorists have to 'suffer' increasing legislation to compensate)
In a time of war or emergency, fair enough but general use 'on a jolly'?
Anyway, a supercharger and turbo would allow much smaller ports allowing side seals to be moved into outer covers, ceramic coatings less heat loss.
I still see issues with rotor expansion, one side of lobes being very hot and the other (relatively) very cold.
Maybe multiple intake/exhaust ports to induce extra swirl plus even out massive temperature gradient?
As diesels are direct injection, very high boost pressure can be used for scavenging, fuel being injected as usual during the burn cycle should allow a reasonably high rpm.
I would think it won't be a problem to fit inboard oil seals to main bearings then use pressure fed mains at least, reducing cost and weight even at expense of adding oil pump and reservoir?
Using 'specified' (two stroke) oil would allow a bleed off to lubricate internal gears.
Service interval would consist of changing spark plugs and topping up oil.
I was waiting for this one :) thanks for the analysis, we knew the whole "it changes everything!" was BS, but you quantified it
Suggestion for future videos: Why timing chain guides, made of plastic, keep failing, even in best cars (BMW, Maserati, Bentley) and what could be done to prevent it. Suggestion no.2: what are the most reliable modern BMW engines (e... da poludi čovek u Americi, nema šta da se odabere, a da nije Toyota). Suggestion 3: sad story about self-destructing electric water pumps.
Top 5 reliable engines making about 300 hp, 400 hp, 500 hp...
Svako dobro i pozdrav i Hjustona
Thanks. I first thought "20 minutes on some new miracle engine?!?!?! You gotta be kidding me!" But figured what the heck, give it a couple of minutes, and next thing I know, you're wrapping it up and I've learned a lot and wondering "Hey! You promised 20 minutes!" and lo and behold, it WAS 20 minutes.
Really really good presentation.
another benefit of the Wankel is that you can stack as many rotors as you want. the design of the Liquid Piston doesn't lend itself to be able to run multiple rotors.
thanx 4 the analysis. it solved a problem I had with making a rotary steam engine using Wankel's design.
Another great video, wish you were around when I was studying mechanical engineering in college in the early 80s.
Your explaining is as always so clear for a noob as me. Thanks! Was pleasant and informative! 👍🏻
I was glad yo see you have a look at this. Ive seen enough thumb nails on youtube i knew it was out there, but didnt think most of them would look at the realistic failings of a unique design. I write this as an old mazda rotary fanboy, sitting in my living room next to the 12a rotor thats an ornament. I appreciate different, weird, obscure, abd overall creative engine designs, being fully aware that so many of them are flawed. I think of them more like art, i appreciate it for the creativity, the design and engineering, but comfortable with them being ultimately kinda useless.
Fascinating, as usual! Always brain food here even for my tired and slow 73 year used cranium. Ah to be young and snappy again.
Regardless, a real blast hearing from a real engineer (as fast as this non-engineer can tell ...LOL). Thx again.
I love how honest these videos are