*Warning!* A little derivation will be involved, but it will be worth it! BMEP is fascinating! If you watch through to the end, I'm 99% sure your mind will be as blown as mine was researching for this video! Really cool stuff, like how Ford shows up Ferrari with the Mustang, how Rolls-Royce builds a head-scratcher of an engine, and if naturally aspirated engine mods are actually worth doing. Hope you enjoy!
@@rat_king- Unless you know the volumetric efficiency for each, there's no way to know how much air each is taking in. An engine with 15 PSI of boost has double the air of naturally aspirated engine, but if that naturally aspirated engine is operating at 120% volumetric efficiency, the engine with 15 PSI of boost actually only has 66% more air, not 100% more.
@@Mexxx65 to be honest though. It actually is mine and has been for a while. When I am finished with college and have a real job, that is the car I am buying.
Exactly. It’s meant for effortless and unnoticeable acceleration. It’s not meant to be super powerful like a 458. It’s meant to waft down the road without bothering its passengers
This is one of your best physics lessons in my view. I’m an earth science teacher who enjoys watching other great teachers teach. I’ve also enjoyed working on, maintaining and analyzing engines, airplanes, cars and motorcycles since I was a child, the offspring of an engineering wizard. So I like the topics you discuss. You have a great teaching style. I hope you keep this kind of thing up for years to come. We need more teachers like you who can inspire as well as enlighten!
To be fair to Rolls, they want that engine to be as quiet as possible, and to last at least 10 years without needing an overhaul, while the Ferrari is likely to not make the distance, and in general will not be a daily use car like the Rolls. Thus run the engine in a lower stress region, but have the turbo small to maker it accelerate fast off the mark, giving the impression desired of "effortless power", the exact opposite of the Ferrari, which is meant to be heard.
@@davidstepan8490 The Ferrari V12 is one of the most amazing engines out there right now. Who wants to live in a world where every car is a small turbo 4 cyl with 2000ccm or even worse: only electric cars. Be glad for the variety.
That's your fault that you didn't find the beauty in math/physics, not your teachers lol. You were, at least then, just Naive. Anything you could imagine, can be explained by math/physics/chemistry. Nothing has been created by accident. It's a beautiful thing when you start to realize how things work isn't it!
@@j.m.7907 Teachers rarely do anything to incentivize such discovery with math though. Math is extraordinarily dry for most without some practical applications to tie it to.
You're right about what you said. But the biggest issue is actually our education system. If they want most if not all children to succeed in school, then they need to be teaching us in ways that will cater to our interests and strengths. You can't have an education system where only some people will succeed and others won't, that's a flawed system. Unfortunately, that is the reality and it's sad that we pay taxes to a flawed education system.
Joel West I took a physics 101 type class and the professor made it fun by showing practical applications that everyone could relate to. Way better than any science class I had in high school. I actually looked forward to that class.
I’m glad there’s another smart person out there thinking in engineering terms. Years ago, when I talked like this in my engine building class I got that “deer in the headlight” look from the instructor. Thanks for a great video. Now onto compression ratio, quench area and L/D intake valve calculations. Yes!
Can you make an online university just for car stuff like this. Right now with isolation and everything. I would be the first student. Great vid as always ! Up the Mazda with the 12.6 !!
@@EngineeringExplained Speaking of the Mazda, I'm surprised you didn't find the BMEP of the 2019 and later models. The tuning has been quite significantly revamped, or so I've heard. The power figures match that statement, too, with a pretty significant increase for such a small displacement. And yeah, I know the 2016 is the model you own, but come on, that thing basically copy pasta'd the Mazda 3 engine. Edit: just searched it up, and yeah, the 2019 model saw an increase in almost 30hp which is like 20%, insane!
I'm going to be so cool at parties. Too bad we're in quarantine and my dogs don't understand anything other than if they sit long enough they get peanut butter.
I am too lazy to do it and maybe I lack some of the variables but I would really like to know the BMEP of the m133 2l 4zyl Engine in my A45 with 381Hp would have. And more so the new m139 with 2l in the current A45 at 420HP..
as a person who studied both advanced mathematics and graduated from an automotive college I appreciate the effort you came up with equation to calculate BMAP. Also why a Rolls Royce V12 Twin Turbo has a less effective BMAP is simply because it was never meant to be a race engine and was based on an old design meant more for comfort and low end torque. However the 458 engine is a work of art. No surprise it won several award for best performance engine, highest HP per liter and also one of the highest revving engines on the market at the time. All of it being beaten by the Aston Valkyrie, but even so the 458 is still a mass produced sports car with all the warranties and probably doesn't need be rebuild every 50/100ks like most hypercars. Shows how much NA engines has evolved over time.
I would really be interested in a video about BMEP calculations for rotary engines. I know they dont have many "similar engines" to compare with, but it interests me nontheless. Great video as always :)
lmao, I don't even have to watch the video to figure out that I'm not gonna understand anything. But I watch it anyways cause it makes me feel like I know about cars.
Problem is I understand, I really do, but chugging down all those informations in 16 minutes is hard so I forget everything a the end. His whiteboards are between 1 and 2 hours of physics class
I think these videos are very useful, especially for us mech engineering and automotive students, but you make it easy to understand even for other people. Keep doing this good work
And that's why I did get straight A's in math - not because the teacher used automotive as the example, but I turned every example into an automotive, railroad, or machinery example!! Geometry and math were fun and I could understand the formulas in detail!!
I did some calculations on my 1973 volvo p1800es and it turns out that it has a surprisingly good bmep of 12.15 bar. that got to be really good for a small displacement inline 4 from the 70s and you're wrong. the best sports car ever made is the volvo p1800. it is the best looking if you ask me, it is raw, sounds great, drives great, pretty quick and since there is absolutely nothing helping you driving the thing, not even power steering do you get the purest road feel of any steering method.
8:58 "... extraordinarily expensive and super fast." LOL I love how you are working the geeky sense of humor into the videos. Thanks for another great video.
Think of it like this, who do you want to teach you math, an old college teacher that doesn't care about real world scenarios, or this guy, comparing everything to car engines? This guy wins hands down. But then again, I don't hate math that much.
Karam J: Amen - if I’d had a teacher like him back in the day, maybe I wouldn’t hate math. (Of course that would had been before he was born) - I’m thankful for guys like him.
"But think of how much more interesting people will find you at parties when you say words like 'Brake Mean Effective Pressure' instead of 'torque'... they'll walk away from you" You mean "Keep their social distance". Also... how are you having parties?
I have to say first how much I enjoy your videos. Your ability to use equations to describe your point is impressive. I was fascinated as well when I learned that engineers were able to get over 100% efficiency out of a naturally aspirated engine. One thing I noticed you neglected to mention in that is how important valve timing, overlap, and size play a roll in both air velocity and pressure. They use the exhaust valves scavenging effect to draw fresh air in like a vacuum during the overlap to maintain air speed. Also why the ratio of the intake valve to exhaust valve size can be so critical. Again hats off to you for super fun content. Thank you.
I did this calculation on a 82 normally aspirated 2.8L Diesel Datsun 810 Maxima and compared it to my 09 BMW 335I 3.0L twin turbo. The difference was amazing. I thought that the 80hp old diesel engine was bulletproof because of the nature of being a diesel. But it had such a low BMEP that the engine was never under much stress.
Great video! Two things come to mind: 1. The power stroke does not end at bottom dead center, it ends when the exhaust valve opens. This typically happens at 120-125 degrees after the piston reaches top dead center, so for the 55-60 degrees remaining after the valve opens, the cylinder pressure is effectively zero. I guess that BMEP means the average pressure over the 180 degrees from top to bottom, despite there being no pressure for those 55-60 degrees? 2. Two engines with the same BMEP, the same displacement, and the same RPM can have quite different mid range torque and thus power. If one of them has a very long connecting rod and the other a short connecting rod, the long rod engine's piston will "dwell" for a longer period near the top of the cylinder while combustion is taking place, thus developing far more pressure than the short rod engine, and it will have way more power in the middle of the RPM band. Why? Draw this out on a piece of paper and you will see why. Draw a crankshaft throw and a connecting rod/piston that is long and another one that has the same stroke but a rod half as long. Imaginarily move the long rod's crankshaft 15 degrees or so and see how far down the piston moves. Now, do the same thing with the short rod drawing- You will see with the short rod the piston moves FAR MORE than with the long rod. Since the exhaust valve opens typically while the mixture is still burning, the dwell period of the long rod design allows more of the charge to be burned before this happens which produces the same BMEP but with more actual torque and power for the long rod design. Jason, you ought to do a video about this effect. Volkswagen used very long rods in the VR6 engine just for this reason.
Sorry, item #2 is not true. By definition, if two engines have the same BMEP , same displacement, and the same RPM, then they will produce exactly the same power. This is by definition and is not subjected to any variation in other engine parameters. Now, WRT long connecting rod, you will have higher dwell time at TDC, and you will have higher heat loss to the engine's combustion chamber at lower rpm, when there is already plenty of time for the fuel to combust, higher propensity for detonation that you may have to reduce compression ratio, thus reducing top-end power and torque...so low-end torque will suffer, in exchange for may be higher top-end power when there will be more time for combustion at top-end RPM, but, you must reduce compression ratio, which will affect top-end power. Furthermore, longer connecting rod will make your engine more bulky, heavier, and higher reciprocating mass due to the higher weight of the con rod, which will require beefier bearings and pins...that may affect top-end RPM...engineering is the art of making compromises.
@@kennethalbert4653 That's not right. Prostrock will run a shorter rod than optimum so they can use a lower deck height and straighten the inlet port to the manifold. Basically you are relying in atm pressure to fill the cyl so it has priority, ie, a higher magnitude of importance, than small effects like rod length. In 2007 a 500cu Prostock was making about 1500hp@10,750, so at 3hp/cu NA they must be doing something right. lol.
BMEP is an average, ie, more initial and less latter evens out. Port velocity has more of an effect in making torque then rod length. With a 2-valve engine we make max TQ when inlet port is designed to run at port velocity of 500-550ft/sec. NA engines are limited to a airspeed of 0.6mach(700ft/sec) before they go into sonic choke and stop producing power. If you want to see the influence of ports look at the LS1. It has a cam with an operation range of 3500rpm, but the engine will rev to double that because the port hits 700ft/sec at 7500rpm. The myth that a long stroke engine makes more torque because of the stroke is wrong. It makes more TQ down low because it has a small bore that only fits small valves and small ports, and this means the port hits it's velocity limit at a low rpm.
I'm a Lab Tech...I worked in the Knock Lab for about 10 years. We ran the 3C engine to rate 100 ll Aviation fuel. We used B.M.E.P. and F.M.E.P. and I.M.E.P. to do our calculation for an Aviation fuels Octane rating. The 3C rating is the A.S.T.M. standard for Aviation fuel octane rating as well as the Lean rating on a M.O.N. engine. Same engines 3C is forced induction and M.O.N. is naturally aspirated
Engineering Explained... is really the perfect name for this channel. I've learned so MUCH cool stuff on here! Thanks Jason for continuing to come up with fantastic video content, and making it INTERESTING. Stay safe amigo!
I think some people refuse to believe that for a daily driven car, top end power isn't as important as how the power builds up and how the car handles. Too many people think that they drive at redline 100% of the time and forget about things like torque and power to weight ratio.
It's torque/displacement with a unit conversion to make it a pressure unit. You can write a long looking equation to convert to work then to the pressure it would take for that volume per rotation which might seem easy in metric because it's a very base 10 system. However metric also make distinctions between force, mass, and weight and newton's take earths acceleration of gravity into account and the rotational nature of torque measurement means a pi is involved. Imperial units aren't any better as the unit for torque and work are sometimes expressed the same way and there are coefficients on practically every unit conversion. To avoid making errors I'll just write down some conversion factors below. Maybe that doesn't break it down but for comparison purposes between engines you can get an idea. Normally aspirated engines can be compared easily and it says a lot about how well they are tuned. Boosted engines have a bigger challenge with heat management and might also make a different decision about the engines ve vs the boost used and other things. You can make dozens of comparisons between the same 2 engines normalizing for different factors but how you weight them in your mind as important is somewhat arbitrary. For nm/l to bar it should be nm torque/litter displacement * 0.12566 = bar bmep Bar to kpa is bar * 100 = kpa to express it in kpa Lb-ft/In³ (foot pound per cubic inch) to psi bmep is lb-ft torque ÷ cubic inches * 148 = psi Psi to bar is psi * 0.0689
This was a really good video chocked full of interesting information and presented very understandably. Just one question, though: For distance you used the stroke, or the distance the piston travels in one half a revolution during the power stroke. For the time, you used the revolutions per second divided by 2 since the power comes only every other revolution. But, that’s the entire revolution, and the power stroke is only half a revolution, so shouldn’t you divide by 2 again, or rev/sec/4, to get the actual time the piston takes to travel the power stroke? (And for a 2-stroke engine, you would divide by 2. ) That would make MEP = 8 * Torque * RPS / Vd, or twice what was presented.
Although I start to glaze over with that mathy stuff, your point was well made. It solidifies my current state of auto buying, "if doesn't have forced induction, I'm not buying it", more torque at lower RPM makes driving on the street more fun...
@Jason There is another way how do I compare engines (actually very similar to yours but a bit more convenient from my point of view). Here is my statement: Well engineered gas NA engine can produce 100 Nm of torque from a 1 L Mazda 6 Skyactiv-G -2.5L 258 Nm - perfect engine Toyota Camry V6 3.5L 357 Nm - perfect engine Chev Epica 2.0L 192 Nm - very good engine Toyota Carina E (1996) 1.6L 141Nm - just good You even can compare Turbocharged and NA engines in this manner. For example my Honda Accord 2.0T has 370Nm, so it is more or less equal to well engineered 3.7L NA engine. And it is, as 2.0T is a bit faster than 3.5 L NA from previous generation
I found a formula sometime ago that used the maximum torque the engine made in lb/ft, multiplied by 2473 then divided by the cubic capacity. e.g. 425(lbs/ft) x 2473 / 5665(c.c.) = 185psi [~200psi being about the upper limit for N/A engines]
The constant 2473, will come about as the result of multiplying an assumed rpm(that of an average rpm for peak torque?) by the necessary unit conversion constants. Thus the formula will estimate on the high side for engines that make peak torque at lower than the assumed rpm. And estimate lower thsn true BMEPs for engines that make peak torque at higher than average RPM.
Hi, Jason. You forgot to mention your BMEP of your previous sport(ier) car. The F20c from the HONDA S2000 has a BMEP=13.1. And that's on a 20+ year old design! Take that, Miata!
"...but think about how much more interesting people will find you at parties when you use words like 'Brake Mean Effective Pressure' as opposed to 'torque'; they'll walk away from you." And you'll never be found at parties again since you'll never be invited! BRILLIANT!
by god my eyes have been lit up while watching this video, i feel enlightened. The last part where you find the potential maximum horsepower of your own engine is so cool.
So I saw the notification for this video while procrastinating on my Physics homework. Somehow you explained my physics homework better than my teacher could, and made it enjoyable too. Your videos are awesome, keep up the great content!!
please include motorcycle engines in your videos, they have impressive power for their displacement (200 HP per Liter is not uncommon for street legal bikes). For example the 2019 Suzuki GSX-R1000R has a BMEP of 14.83
My 97 Honda cbr 600 f3 with 66 nm has 13,85 and my 84 gpz 900 r with 85 nm has 11,65. Engine efficiency and design improved a lot between 1984 and 1997! In motorcycles you also see the same engines being tuned for torque in road and touring versions and hp in race versions.
P.S.: RR "low" BMEP for a turbo-powered engine means it is built to last (quite the opposite regardng the Ferrari engine). Also, increasing BMEP while maintaining the same engine original components (pistons, rods, cranckshafts) will ALWAYS result in shorter engine life simply because the original materials were not designed/manufactured to stand the additional stress.
Dear Jason (and/or his viewers), **Question** How is it possible for a naturally aspirated engine to exceed atmospheric pressure? Context: I'm a math teacher turned data scientist who was recommended this video because it had lots of math. I showed it to a bunch of friends I grew up with who are professional and hobbyist auto mechanics, and they were curious of the answer to that question. Other feedback: Your mathematical derivation is wonderfully clear and very well contextualized! I especially like how you explained why it is necessary to divide by 2 at the end of eq 4 and your careful handling of torque (no pun intended) in eq 7. How long did it take you to prepare the notes for this? I hope you and your family (and all of your viewers) are staying safe and healthy! Sincerely, Joe
Well done! I learned a lot! Now please explain diesel engine NVH apart from high pressure inside the combustion chamber. How some diesel engines are quieter than others.... AND high BHEP on low displacment engine does it have reliablity issues in the long run with that too much stress?
it's the rate at which pressure increases in the diesel that's the noisemaker, some alleviate that with 1 or 2 pre injections. Also a plastic sump to dampen noise coming out the bottom helps
Turbocharger converts part of the noise into the turbine rotation, which used to pressurize air intake (ofcourse, exhaust pressure and heat are converted too). Modern common rail injector squirts preinjection before main injection events to dampen vibration by harmonics. Also some engines actually have intake throttle, like my Chevy Captiva. While it mainly functions to maximize exhaust gas recirculation (EGR) system, it has side effect of noise reduction. Also modern heat resistant foam that is used under the engine cover and the engine hood also absorbs noise. Balance shaft is used as well to reduce vibration and therefore noise.
10:19 So I did a bit of math myself (cause I'm fun like that) and I calculated that the EMD 12-1010J, a 16.6L V12 locomotive engine with a 1 foot stroke length - which redlines at 1000 rpm - gets *_247.95 bar_* of BMEP. So while short-stroke, high-revving engines are very efficient, the same can be said of the huge, slow, torquey engines on the other end of the scale. Just something I found interesting
The problem i have with comparing engines by their power is that we never factor in the one thing that /actually/ matters: reliability/longevity. BMEP really is showing how "high strung" an engine is.
@@dernachtmannkommt Lets not forget the Brutale 1000rr 14.6 its a lot more comfortable to ride than superbikes ;) well until you going over 180 then you really miss having a fairing.
I honestly don't like Math that much. I quite hate solving difficult problems. But when it comes to computing related to cars, I always get interested. I hope Jason is my Math teacher back in high school, so I wouldn't get bored of Math. But good thing that I am more interested than ever because of videos like this. Thank you Jason for making Math interesting. Hehe!
Yes, a cylinder can fill more than "100%" if the air charge has momentum or a higher than atmospheric pressure wave forcing the charge in. This is why intake and exhaust runners are tuned.
Yeah, I've been noticing for years now that when it comes to motorcycles, despite wild variations of HP/litre between different models; there isn't that much variation in terms of torque/litre, with most of them being somewhere around 9-11 kgf.m/litre (keep in mind that virtually all bikes are naturally aspirated, AFAIK the only factory non-naturally aspirated motorcycle nowadays is the supercharged Kawasaki H2/H2R). Jason, have you ever thought of comparing engines in the form of some integration of the power curve? Of course this would require some consideration; for instance if it were integrated in terms of rpm, you would probably have to choose an arbitrary range of rpm (say the top 3000rpm with greatest power), and this would not be ideal if you were to compare between engines with significant variations of the rev limit... So I guess it could be in terms of a certain proportion of the rev range, for instance the top 50% of the rev limit (for a 6000rpm redline, this would mean the range of 3000 rpm with greatest power). I believe something like this would give you a more significant value to compare the ability to accelerate than simply peak power.
"Non-aspirated"? Never heard it called that before, doesn't really make sense to me either. Naturally aspirated or forced, the engine is supplied with air so would therefore be aspirated.
The s2000 would land in the puddle of oil the thing leaks and burns every 1k miles it runs. S2ks are great cars don't get me wrong but they are a bit heavy compared to the competition and they make power way to high in the rev range for a car that is daily driven on a regular basis. For a track car i'd buy an s2k in a heartbeat. For a daily driver i'll take a mx-5 rf so when the top isn't down I can keep the elements off of me and don't get the soft top buffeting like all the other soft top cars I've owned in the past and also when I take it easy commuting I get close to around 40mpg(38mpg was my highest and that was cruising down the highway at around 80mph).
Couldn't be bothered to work out the BMEP, but 76.5 lb/ft per liter puts it at somewhere between the Lexus LFA (73.7 lb/ft) and the Ferrari 812 (81.5 lb/ft). Not bad for an engine that was designed over 20 years ago!
IMHO, it's just an arbitrary number (like max HP), that maybe gives a little insight on the engines, but probably doesn't. It takes into account just the peak torque, but these engines have completely different torque curves and rev ranges. You can say it's the "mean", but it's just such a big shortcut, that the numbers you get in the end won't mean much. To get something more relevant, you probably could use the same math, integrate it through the whole torque curve, and divide it by the rev range. It would reflect much better the effective pressure. Excellent content and beautiful explanation! Loved it.
Great stuff, In the early 80s I began to wonder why porsche and jaguar engines of less than 3.5 litres were putting out more power than 5+ litre V8 engines. It was then that I learned of volumetric efficiency. Great explanation - will do calcs for my daily driver.
I found a new record for lowest BMAP. the 1996-2006 jeep wranglers (and other models) had a 4L inline 6 making 190hp and 225 ftlbs. The BMEP comes out to 9.5 lol. This is actually really surprising to me considering its one of very few gas engines that make quite a bit more torque than hp.
I'm sceptic about all of this, in a constructive way, its nonsense. how do you cancel out the RPS at step 9? the crankshaft and the wheels do not spin at the same ratio, at least you must've explained the particular case of using the 1:1 gear ratio of the gearbox. Then you are making another big mistake, that is to take the torque at the crankshaft, because in step 7 you cancelled out the radius, and if you assume they are the same, you are using the torque at the wheels. Otherwise you'll be taking the crank radius equal to the wheel radius. Cool video anyway, keep it up
A better way of thinking about this is that it an engine with a higher BMEP with more efficiently exert a pressure throughout its entire stroke. Doing so is very nontrivial and means that the intake, exhause, engine balance, etc. etc. have all been thoughtfully engineered. The engine will have to make maximal use of the power stroke, have minimal losses during the exhuast and intake strokes, and be mechanically perfect enough to not dissipate energy in vibrations and heat. On a side note, the way Jason does units is maddening to me as a physicist XD.
I used to operate 18 cylinder, 2800 cubic inch, supercharged aircraft engines, with water-injection for detonation prevention at very high [power settings (2400 HP, using 100 octane fuel.). Although we used Manifold Pressure & Engine RPM as our primary power-setting guidance, each engine also had a nice BMEP (that's "Bee Emm Eee Pee", *NOT* "BeeMep") guage at the top of it's stack, calibrated in Pounds per Square Inch, Mercury. We used this data to precisely set our cruise fuel mixture ratio, as well as monitor overall engine power output. If we wanted to figure out actual HorsePower being developed, we simply multiplied BMEP by Engine RPM, and then divided the product by the mathematical constant "283". As an example, in a high-power cruise you might read a BMEP of 140 @ 2400 RPM. This gave you about 1200 HP Cruise power. I have no idea where the "283" was derived from, but it just always worked for our calculations.
Maybe they should be, but perhaps rich folk are impressed by throwing displacement or boost at engines instead of good engineering. As long as they sell big comfy cars I guess.
@@CompTechs There's plenty of great engineering in that engine. You can make an engine with massive BMEP by simply lowering the hell out of compression ratio, fitting a massive turbo and intercooler and cranking up the boost until just before it blows up. Doesn't make it a particularly impressive feat of engineering. When the metric you're using to measure the quality of an engine gives you results that say an MX-5 is as good as an LFA that's a pretty big giveaway that that metric by itself isn't particularly useful or relevant.
@@CompTechs damn, people like you know nothing about cars... Rolls royce couldn't care less about a performance Stat such as BMEP, since their cars have a completely different purpose. The engine needs to be silent, robust and definetely not high performing (good acceleration is not important in such car). The rolls royce is perfect in that case so stop mixing up stuff you know nothing about. It's like saying "F1 cars are slow because they have low torque". You guys Completely missed the point.
K20 makes about 100Nm/ liter if I'm not mistaken, with the Mugen FD2 Type-R being the most impressive at 110Nm/ liter and it maintained that number until peak power. The BMEP thing just translates to Nm/liter, and the maximum potential for N/A motors is about 120Nm/ liter and 105-110Nm/ liter at peak power.
Respect to you Jason, you take the craziest concepts and explain them really well. I think maybe it’s a gift. I had a philosophy professor in college who had the same gift. Others could talk The Who semester and it made no sense. Not here. This video was SO interesting. I hope you consider applying to other types of engines. Cool.
So I'm about 5 minutes into the video. Is this basically another form of a way to say power per liter? Edit: got to 6:30 and wow, I surprised myself that I was right. My mama said I was smart.
Is clear that you have no idea what you are taking about. Torque and power are in a direct relationship, so simplistically speaking they tell us the same thing. What really matters and people are not aware is that all manufactures specify only peak power/torque and what is actually important is power/torque curve over the nominal RPM range of the engine.
Torque is what people feel when leaving stop sign. And, people feel that many times when they drive. Peak horsepower (or peak torque) is rarely felt, if ever, in normal use. Let's keep the comments respectful.
Problem is, no one knows the formula for the area of a Dorito. It's kind of like the English word that rhymes with orange. We're not tryna create any blackholes here.
Hmmm there must be a way to figure it out, technically distance traveled would be 1 rotation right? And you can get the surface area of the face, also I'm not sure how many times it fires throughout that rotation though
You'd multiply by a ratio. I don't remember the exacts of the wankel design. Is it three burns per revolution and two engine revolution equals one crankshaft revolution? Basically, get a ratio that removes the differences in power delivery.
My ‘06 Acura TL has a stock, naturally aspirated SOHC 3.2L V6 equipped with a variable volume induction (VVI) intake manifold setup that utilizes the ‘Helmholtz Resonance Effect’ to introduce a mild supercharged intake boost for improved induction efficiency. This effect is essentially the same as how (tuned) engine exhaust headers work. They apply a pulse or tuned scavenging effect that sort of sucks the exhaust gas out improving flow efficiency with accompanying increase in power. All to say cars employing the gimmick of a VVI, naturally aspirated intake increase charge efficiencies w/o the use of a turbo of a supercharger.
*Warning!* A little derivation will be involved, but it will be worth it! BMEP is fascinating! If you watch through to the end, I'm 99% sure your mind will be as blown as mine was researching for this video! Really cool stuff, like how Ford shows up Ferrari with the Mustang, how Rolls-Royce builds a head-scratcher of an engine, and if naturally aspirated engine mods are actually worth doing. Hope you enjoy!
Remind me why there is no correction factor for boosted/ at altitude engines? get total apples to apples comparison
high regards From Bulgaria, great content every time,you are my engine mentor
Many thanks Jason. you explained it better than my high school teacher, I finally understood that after 40 years.
@@rat_king- Unless you know the volumetric efficiency for each, there's no way to know how much air each is taking in. An engine with 15 PSI of boost has double the air of naturally aspirated engine, but if that naturally aspirated engine is operating at 120% volumetric efficiency, the engine with 15 PSI of boost actually only has 66% more air, not 100% more.
Neat.
Jason is a BMEP.
Big Math Equation Person
@@Mexxx65 ikr..
342.
Elementary school level of math and physics. I mean I love it but it's as simple as it gets!
@@Mexxx65 its a good comment. Big math did occur.
GFNoivern Its called Engineer, Greetings colleague Jason , Electrical and Mechanical engineer here👊
Jason lowkey flexing that his brand new miata is as cool as the LFA
9:20 he couldn't contain his smile
"It's basically an LFA"
- me at the next cars & coffee
@@EngineeringExplained Is this the new "My s2000 is basically a Ferarri"? Now i see why you bought it.
@@Mexxx65 to be honest though. It actually is mine and has been for a while. When I am finished with college and have a real job, that is the car I am buying.
@@Mexxx65 Gotta shove them facts boy!
Me: "is this going to be a normal video?"
Video starts with Jason in front of a wall of math
Me: "ahh, just like I remember."
I feel you.
Shitty how much physics have to work for your *brrrap*
The physics interests me MORE than the brap
" A WALL OF MATH " LMFAO.
@@NoWr2Run WALL OF DEATH🤣
GAY AF
"...they'll walk away from you." - You said that with conviction. You must have experience!
Doesn't even phase him.
I like it.
Fun fact: The Cosworth DFV has a BMEP of 13.9. Quite impressive for an engine made back in 1967.
Ah yes, the Universal race engine of the 70s
"...IT BREAKS THE SCALE (that I made up)..."
I almost spat my coffee when he said that lol
That's just CRAZY!
@@EngineeringExplained I chuckled because it's just so... you!
Bruizey It really is very characteristic of Jason, particularly the delivery!
The Rolls-Royce engine is most likely optimized for smooth power delivery (flat torque curve) and quiet operation.
Yeah! That sounds logical! Given the fact that you are driven in a Rolls not driving it.
Exactly. It’s meant for effortless and unnoticeable acceleration. It’s not meant to be super powerful like a 458. It’s meant to waft down the road without bothering its passengers
good job, you watched the part of the video where he explained exactly that.
Great that's all I came here to see debunked. Thx
Turbochargers are pretty effective as an additional muffler. Keeps engine noise down when combined with a good exhaust system.
At 120% of natural air pressure you’re looking at nearly 3 lbs of boost with an intake, this is very impressive!
This is one of your best physics lessons in my view. I’m an earth science teacher who enjoys watching other great teachers teach. I’ve also enjoyed working on, maintaining and analyzing engines, airplanes, cars and motorcycles since I was a child, the offspring of an engineering wizard. So I like the topics you discuss. You have a great teaching style. I hope you keep this kind of thing up for years to come. We need more teachers like you who can inspire as well as enlighten!
To be fair to Rolls, they want that engine to be as quiet as possible, and to last at least 10 years without needing an overhaul, while the Ferrari is likely to not make the distance, and in general will not be a daily use car like the Rolls. Thus run the engine in a lower stress region, but have the turbo small to maker it accelerate fast off the mark, giving the impression desired of "effortless power", the exact opposite of the Ferrari, which is meant to be heard.
the engine is also designed to have a very flat power curve over the rev range, to make it feel smoother
You're absolutely right. 👌
@@tommihommi1 Also true. 👌
Great point on reliability. The topfuel dragster engine can only go 1/4 mile between rebuilds to achieve its number.
@Nabil Sabli "Thats how impressive rolls engine is in terms of refinement" You mean "BMW engine", right? :)
Someone: hey my Ferrari V8 is amazing
Jason: (takes out a whiteboard)
nice. I'd sit and listen.
Actually, the V8 458 IS amazing.. It's the V12 that isn't (as much)
@@davidstepan8490 The Ferrari V12 is one of the most amazing engines out there right now. Who wants to live in a world where every car is a small turbo 4 cyl with 2000ccm or even worse: only electric cars.
Be glad for the variety.
@@nik7bkh965 who would want to live in a world with no air microparticle pollution
@@MaxxerG I know right, I'll keep my freedom to get lung cancer and other respiratory problems, and brain damaged kids thank you very much
"only compare similar vehicles!"
> compares the mitsubishi mirage with the ferrari 458
haha very cool video
😅
I actually used a Toyota Echo for pulling a tree once 😅 it worked
@@m.morininvestor9920 prithee allow me to bethink about thy actions...
its not smart to pull a tree with a car... also "tree" could mean anything.
Use
Use d
The joy of learning how it all works. I love "Engineering" when it is "Explained". Thanks Jason for a great video as usual.
If I was back in high school with him as my teacher making these equations relevant to my interests then I would of been an A+ student
That's your fault that you didn't find the beauty in math/physics, not your teachers lol. You were, at least then, just Naive. Anything you could imagine, can be explained by math/physics/chemistry. Nothing has been created by accident. It's a beautiful thing when you start to realize how things work isn't it!
@@j.m.7907 Teachers rarely do anything to incentivize such discovery with math though. Math is extraordinarily dry for most without some practical applications to tie it to.
You're right about what you said. But the biggest issue is actually our education system. If they want most if not all children to succeed in school, then they need to be teaching us in ways that will cater to our interests and strengths. You can't have an education system where only some people will succeed and others won't, that's a flawed system. Unfortunately, that is the reality and it's sad that we pay taxes to a flawed education system.
JOEY M You’d be an awful teacher with that attitude. Literally every science educator out there would disagree with you.
Joel West I took a physics 101 type class and the professor made it fun by showing practical applications that everyone could relate to. Way better than any science class I had in high school. I actually looked forward to that class.
Basically:
BMEP (bars) * 8 = Torque from 1 liter displacemant [4 stroke engine]
BMEP (bars) * 16 = Torque from 1 liter displacemant [2 stroke engine]
for US:
BMEP (psi) * 0.544 / 61 = Torque from 1 cu inch displacemant [4 stroke engine]
POWER:
Torque (NM) * RPM * 0.104 / 735 = Power (PS)
Torque (lb-ft) * RPM * 0.142 / 745 = Power (HP)
Thank you.
Was wondering. Thank you so much
"Spreadsheets Heck Yeah!"
take my thumbs up EE :p
He's literally the only person on RUclips who is capable of proving an MX-5 is just as good as an LFA.
yeah because an mx5 does 0-60 in 3.6s huh. LOL
Just as good in one specific metric that nobody ever heard of and means little in the real world, yeah :-D
Proving? i think you mean pretending
Its pretty much self evident, but the maths help ;-)
@@soundseeker63 when you say 'no one's ever heard of' you mean apart from all those mechanical engineers who use this daily?
"it breaks the scale -- that i made up" sums up my life
You meant to say it sums up your eating habits?
I’m glad there’s another smart person out there thinking in engineering terms. Years ago, when I talked like this in my engine building class I got that “deer in the headlight” look from the instructor. Thanks for a great video. Now onto compression ratio, quench area and L/D intake valve calculations. Yes!
Can you make an online university just for car stuff like this. Right now with isolation and everything. I would be the first student. Great vid as always ! Up the Mazda with the 12.6 !!
Here you go! ruclips.net/user/engineeringexplained
Bosch Automotive Handbook. You're welcome
@@EngineeringExplained Speaking of the Mazda, I'm surprised you didn't find the BMEP of the 2019 and later models. The tuning has been quite significantly revamped, or so I've heard. The power figures match that statement, too, with a pretty significant increase for such a small displacement. And yeah, I know the 2016 is the model you own, but come on, that thing basically copy pasta'd the Mazda 3 engine.
Edit: just searched it up, and yeah, the 2019 model saw an increase in almost 30hp which is like 20%, insane!
@@EngineeringExplained iiiii see what you did there!
@@olegkolesnikov7155 It's 12.9
I'm going to be so cool at parties. Too bad we're in quarantine and my dogs don't understand anything other than if they sit long enough they get peanut butter.
Jacob Wagner what the hell does this comment have to do with this video? Go like farming elsewhere
My BMEP is bigger than yours
I bet they get the peanutbutter. 😉😉😉😉
The kitty gets the milkshake and the bunny gets the pan...cake!
@D.O.A. 🤣
15:30 "Let's say this is a 2.0L engine we're modifying". Gee, I wonder why? ;)
I am too lazy to do it and maybe I lack some of the variables but I would really like to know the BMEP of the m133 2l 4zyl Engine in my A45 with 381Hp would have. And more so the new m139 with 2l in the current A45 at 420HP..
as a person who studied both advanced mathematics and graduated from an automotive college I appreciate the effort you came up with equation to calculate BMAP. Also why a Rolls Royce V12 Twin Turbo has a less effective BMAP is simply because it was never meant to be a race engine and was based on an old design meant more for comfort and low end torque.
However the 458 engine is a work of art. No surprise it won several award for best performance engine, highest HP per liter and also one of the highest revving engines on the market at the time. All of it being beaten by the Aston Valkyrie, but even so the 458 is still a mass produced sports car with all the warranties and probably doesn't need be rebuild every 50/100ks like most hypercars. Shows how much NA engines has evolved over time.
I would really be interested in a video about BMEP calculations for rotary engines. I know they dont have many "similar engines" to compare with, but it interests me nontheless. Great video as always :)
Each rotor is equivalent in timing to a 2-stroke cylinder.
Jason basically speaking gibberish the entire time:
Me: Yes, I completely understand
lmao, I don't even have to watch the video to figure out that I'm not gonna understand anything. But I watch it anyways cause it makes me feel like I know about cars.
As my professor used to say "IT'S ALL ABOUT THE UNITS"
Problem is I understand, I really do, but chugging down all those informations in 16 minutes is hard so I forget everything a the end. His whiteboards are between 1 and 2 hours of physics class
if this is gibberish to you, you might need to go back to highschool
ME RIGHT NOW
I think these videos are very useful, especially for us mech engineering and automotive students, but you make it easy to understand even for other people. Keep doing this good work
If my math teacher in highschool used cars as a way to teach equations, I would have passed every class with an A+.
@B
(Estimated Seeds per watermelon * 10) -(estimated seeds per watermelon * 4) ≈ number of seeds
@B
I can't figure it out.
Is there a way to write an expression for that?
Ahh the old trick question, where knowing math is irrelevant but being good at English is.
My answer 0 I only eat seedless water 🍉
And that's why I did get straight A's in math - not because the teacher used automotive as the example, but I turned every example into an automotive, railroad, or machinery example!! Geometry and math were fun and I could understand the formulas in detail!!
I did some calculations on my 1973 volvo p1800es and it turns out that it has a surprisingly good bmep of 12.15 bar. that got to be really good for a small displacement inline 4 from the 70s
and you're wrong. the best sports car ever made is the volvo p1800. it is the best looking if you ask me, it is raw, sounds great, drives great, pretty quick and since there is absolutely nothing helping you driving the thing, not even power steering do you get the purest road feel of any steering method.
Nice car bro
8:58 "... extraordinarily expensive and super fast." LOL I love how you are working the geeky sense of humor into the videos. Thanks for another great video.
Perfect timing ! Just today I was looking for this info because found out bmep are always there on every engine spec sheet. Now I know, thank you !
Love cars, hate math - Jason is like my paradox emulsifier
Think of it like this, who do you want to teach you math, an old college teacher that doesn't care about real world scenarios, or this guy, comparing everything to car engines? This guy wins hands down. But then again, I don't hate math that much.
Karam J: Amen - if I’d had a teacher like him back in the day, maybe I wouldn’t hate math. (Of course that would had been before he was born) - I’m thankful for guys like him.
Big Mo - Paradox emulsifier? Now that's a great term! I'm going to use it at parties! That, and BMEP. Cheers!
@@BiggMo Nothing is stopping you from rediscovering the wonders of maths now.
"But think of how much more interesting people will find you at parties when you say words like 'Brake Mean Effective Pressure' instead of 'torque'... they'll walk away from you"
You mean "Keep their social distance".
Also... how are you having parties?
Most people will likely walk away when you say 'torque' anyways 😉
I have to say first how much I enjoy your videos. Your ability to use equations to describe your point is impressive. I was fascinated as well when I learned that engineers were able to get over 100% efficiency out of a naturally aspirated engine. One thing I noticed you neglected to mention in that is how important valve timing, overlap, and size play a roll in both air velocity and pressure. They use the exhaust valves scavenging effect to draw fresh air in like a vacuum during the overlap to maintain air speed. Also why the ratio of the intake valve to exhaust valve size can be so critical. Again hats off to you for super fun content. Thank you.
I did this calculation on a 82 normally aspirated 2.8L Diesel Datsun 810 Maxima and compared it to my 09 BMW 335I 3.0L twin turbo. The difference was amazing. I thought that the 80hp old diesel engine was bulletproof because of the nature of being a diesel. But it had such a low BMEP that the engine was never under much stress.
Ha, I haven’t seen BMEP calculations since my ICE course in Mech Engineering 🤓🤓. Wünderbar
Great video! Two things come to mind:
1. The power stroke does not end at bottom dead center, it ends when the exhaust valve opens. This typically happens at 120-125 degrees after the piston reaches top dead center, so for the 55-60 degrees remaining after the valve opens, the cylinder pressure is effectively zero. I guess that BMEP means the average pressure over the 180 degrees from top to bottom, despite there being no pressure for those 55-60 degrees?
2. Two engines with the same BMEP, the same displacement, and the same RPM can have quite different mid range torque and thus power. If one of them has a very long connecting rod and the other a short connecting rod, the long rod engine's piston will "dwell" for a longer period near the top of the cylinder while combustion is taking place, thus developing far more pressure than the short rod engine, and it will have way more power in the middle of the RPM band. Why? Draw this out on a piece of paper and you will see why. Draw a crankshaft throw and a connecting rod/piston that is long and another one that has the same stroke but a rod half as long. Imaginarily move the long rod's crankshaft 15 degrees or so and see how far down the piston moves. Now, do the same thing with the short rod drawing- You will see with the short rod the piston moves FAR MORE than with the long rod. Since the exhaust valve opens typically while the mixture is still burning, the dwell period of the long rod design allows more of the charge to be burned before this happens which produces the same BMEP but with more actual torque and power for the long rod design.
Jason, you ought to do a video about this effect. Volkswagen used very long rods in the VR6 engine just for this reason.
Ha! Smokey Yunik said "stuff in the longest damn rod you can"!
Agreed - rod/stroke ratio is pretty dang cool, and I'm sure there is a lot more I could learn about it.
Sorry, item #2 is not true. By definition, if two engines have the same BMEP , same displacement, and the same RPM, then they will produce exactly the same power. This is by definition and is not subjected to any variation in other engine parameters.
Now, WRT long connecting rod, you will have higher dwell time at TDC, and you will have higher heat loss to the engine's combustion chamber at lower rpm, when there is already plenty of time for the fuel to combust, higher propensity for detonation that you may have to reduce compression ratio, thus reducing top-end power and torque...so low-end torque will suffer, in exchange for may be higher top-end power when there will be more time for combustion at top-end RPM, but, you must reduce compression ratio, which will affect top-end power. Furthermore, longer connecting rod will make your engine more bulky, heavier, and higher reciprocating mass due to the higher weight of the con rod, which will require beefier bearings and pins...that may affect top-end RPM...engineering is the art of making compromises.
@@kennethalbert4653 That's not right. Prostrock will run a shorter rod than optimum so they can use a lower deck height and straighten the inlet port to the manifold. Basically you are relying in atm pressure to fill the cyl so it has priority, ie, a higher magnitude of importance, than small effects like rod length. In 2007 a 500cu Prostock was making about 1500hp@10,750, so at 3hp/cu NA they must be doing something right. lol.
BMEP is an average, ie, more initial and less latter evens out.
Port velocity has more of an effect in making torque then rod length. With a 2-valve engine we make max TQ when inlet port is designed to run at port velocity of 500-550ft/sec. NA engines are limited to a airspeed of 0.6mach(700ft/sec) before they go into sonic choke and stop producing power. If you want to see the influence of ports look at the LS1. It has a cam with an operation range of 3500rpm, but the engine will rev to double that because the port hits 700ft/sec at 7500rpm. The myth that a long stroke engine makes more torque because of the stroke is wrong. It makes more TQ down low because it has a small bore that only fits small valves and small ports, and this means the port hits it's velocity limit at a low rpm.
Thanks for taking me back 20 years to my IC Engines class!
I'm a Lab Tech...I worked in the Knock Lab for about 10 years. We ran the 3C engine to rate 100 ll Aviation fuel. We used B.M.E.P. and F.M.E.P. and I.M.E.P. to do our calculation for an Aviation fuels Octane rating. The 3C rating is the A.S.T.M. standard for Aviation fuel octane rating as well as the Lean rating on a M.O.N. engine. Same engines 3C is forced induction and M.O.N. is naturally aspirated
Engineering Explained... is really the perfect name for this channel. I've learned so MUCH cool stuff on here! Thanks Jason for continuing to come up with fantastic video content, and making it INTERESTING. Stay safe amigo!
I think some people refuse to believe that for a daily driven car, top end power isn't as important as how the power builds up and how the car handles. Too many people think that they drive at redline 100% of the time and forget about things like torque and power to weight ratio.
Send out the spreadsheet so we can calc our BMEP!! Great video!
It's torque/displacement with a unit conversion to make it a pressure unit. You can write a long looking equation to convert to work then to the pressure it would take for that volume per rotation which might seem easy in metric because it's a very base 10 system. However metric also make distinctions between force, mass, and weight and newton's take earths acceleration of gravity into account and the rotational nature of torque measurement means a pi is involved. Imperial units aren't any better as the unit for torque and work are sometimes expressed the same way and there are coefficients on practically every unit conversion. To avoid making errors I'll just write down some conversion factors below. Maybe that doesn't break it down but for comparison purposes between engines you can get an idea. Normally aspirated engines can be compared easily and it says a lot about how well they are tuned. Boosted engines have a bigger challenge with heat management and might also make a different decision about the engines ve vs the boost used and other things. You can make dozens of comparisons between the same 2 engines normalizing for different factors but how you weight them in your mind as important is somewhat arbitrary.
For nm/l to bar it should be nm torque/litter displacement * 0.12566 = bar bmep
Bar to kpa is bar * 100 = kpa to express it in kpa
Lb-ft/In³ (foot pound per cubic inch) to psi bmep is lb-ft torque ÷ cubic inches * 148 = psi
Psi to bar is psi * 0.0689
Oooooh, more tools for my social distancing toolbox
It is nice to watch a RUclips video that does not bore me with incompetence. Thank you for all the work you put into developing your videos.
I needed you as an algebra teacher. Engines are way easier to understand than random problems
I was playing this video in full screen and my siblings thought this was an algebra lecture........
Tuning your car up to double the horsepower it can make naturally
That's why he named the spreadsheet Heck Yeah!!!
👍👍👍👍👍☺
This was a really good video chocked full of interesting information and presented very understandably. Just one question, though: For distance you used the stroke, or the distance the piston travels in one half a revolution during the power stroke. For the time, you used the revolutions per second divided by 2 since the power comes only every other revolution. But, that’s the entire revolution, and the power stroke is only half a revolution, so shouldn’t you divide by 2 again, or rev/sec/4, to get the actual time the piston takes to travel the power stroke? (And for a 2-stroke engine, you would divide by 2. ) That would make MEP = 8 * Torque * RPS / Vd, or twice what was presented.
No.
That actually makes sense. Should be divided by 4 for a 4 stroke and by 2 for a 2 stroke.
Although I start to glaze over with that mathy stuff, your point was well made. It solidifies my current state of auto buying, "if doesn't have forced induction, I'm not buying it", more torque at lower RPM makes driving on the street more fun...
@Jason There is another way how do I compare engines (actually very similar to yours but a bit more convenient from my point of view). Here is my statement: Well engineered gas NA engine can produce 100 Nm of torque from a 1 L
Mazda 6 Skyactiv-G -2.5L 258 Nm - perfect engine
Toyota Camry V6 3.5L 357 Nm - perfect engine
Chev Epica 2.0L 192 Nm - very good engine
Toyota Carina E (1996) 1.6L 141Nm - just good
You even can compare Turbocharged and NA engines in this manner. For example my Honda Accord 2.0T has 370Nm, so it is more or less equal to well engineered 3.7L NA engine. And it is, as 2.0T is a bit faster than 3.5 L NA from previous generation
I found a formula sometime ago that used the maximum torque the engine made in lb/ft, multiplied by 2473 then divided by the cubic capacity. e.g. 425(lbs/ft) x 2473 / 5665(c.c.) = 185psi [~200psi being about the upper limit for N/A engines]
Excellent
The constant 2473, will come about as the result of multiplying an assumed rpm(that of an average rpm for peak torque?)
by the necessary unit conversion constants.
Thus the formula will estimate on the high side for engines that make peak torque at lower than the assumed rpm. And estimate lower thsn true BMEPs for engines that make peak torque at higher than average RPM.
Hi, Jason. You forgot to mention your BMEP of your previous sport(ier) car. The F20c from the HONDA S2000 has a BMEP=13.1. And that's on a 20+ year old design!
Take that, Miata!
Too bad it weighs an extra 500 lbs..
My Miata develops usable torque over the driving and racing range. I can start smoothly in third gear and race with the standard gearbox
Can I get the spreadsheet you used to calculate every car's BMEP? Asking for a friend.
@Sub Scriptions huh
"...but think about how much more interesting people will find you at parties when you use words like 'Brake Mean Effective Pressure' as opposed to 'torque'; they'll walk away from you."
And you'll never be found at parties again since you'll never be invited!
BRILLIANT!
I'm student in internal combustion engine your videos are great to learn my class in another languages TY
Love the videos, Jason. The math is way above me, but I like to pretend I understand everything you’re saying 😂. It makes me feel smarter
One of the reasons i like his videos, he actually explains the math pretty well, so that anyone could do it pretty much.
@@merlinevseichik9479 that's the definition of a good teacher!
you took the words right out of my mouth that's also why I watch BigCliveDotCom lol
LOL this just boils down to you trying to cost justify putting a supercharger on the new Miata :p
by god my eyes have been lit up while watching this video, i feel enlightened. The last part where you find the potential maximum horsepower of your own engine is so cool.
So I saw the notification for this video while procrastinating on my Physics homework. Somehow you explained my physics homework better than my teacher could, and made it enjoyable too. Your videos are awesome, keep up the great content!!
Did the test for my 2014 Aprilia Tuono and it scores...
13.97! Higher than a Ferrari!
My Mercedes has nearly 20 so way better than you ;)
please include motorcycle engines in your videos, they have impressive power for their displacement (200 HP per Liter is not uncommon for street legal bikes). For example the 2019 Suzuki GSX-R1000R has a BMEP of 14.83
my 1998 r1 have BMPE of 13.8230076758
My 97 Honda cbr 600 f3 with 66 nm has 13,85 and my 84 gpz 900 r with 85 nm has 11,65. Engine efficiency and design improved a lot between 1984 and 1997! In motorcycles you also see the same engines being tuned for torque in road and touring versions and hp in race versions.
My 2015 bmw f800gt BMEP=13.5, and can get around 60mpg. Well done BMW.
I was wondering about bikes, thanks
P.S.: RR "low" BMEP for a turbo-powered engine means it is built to last (quite the opposite regardng the Ferrari engine). Also, increasing BMEP while maintaining the same engine original components (pistons, rods, cranckshafts) will ALWAYS result in shorter engine life simply because the original materials were not designed/manufactured to stand the additional stress.
This is the cost aspect of what he was saying, you are going to have to start moving to exotic materials and finer tolerances to get there.
Dear Jason (and/or his viewers),
**Question** How is it possible for a naturally aspirated engine to exceed atmospheric pressure?
Context: I'm a math teacher turned data scientist who was recommended this video because it had lots of math. I showed it to a bunch of friends I grew up with who are professional and hobbyist auto mechanics, and they were curious of the answer to that question.
Other feedback: Your mathematical derivation is wonderfully clear and very well contextualized! I especially like how you explained why it is necessary to divide by 2 at the end of eq 4 and your careful handling of torque (no pun intended) in eq 7. How long did it take you to prepare the notes for this?
I hope you and your family (and all of your viewers) are staying safe and healthy!
Sincerely,
Joe
Brilliant video. Never has physics/mechanics/mathematics been so much fun and easy to understand! :)
Ah haha... "more interesting at parties " ... like my future wife's reaction when I said "g-force." 😆
There was me about to go “Woooahh my little Skoda is about 15 on that scale”... before I remembered it’s both Turbocharged and Supercharged 🤣
Love those twin charge engines! How is it going?
a twin charged Skoda? WTF.
*3.5 seconds of Google Fu later*
As yes, the wonderful VW 1.4 TSI.
Andy Fisher 2.3 seconds 0-gulag
Skoda felicia fun 1999= 10.6 bar
My 2001 Renault Clio 1.4 8v is only a 10.1 on the scale :(
Too bad this engine doesn't have a large aftermarket, or at least that I know of.
Well done! I learned a lot! Now please explain diesel engine NVH apart from high pressure inside the combustion chamber. How some diesel engines are quieter than others.... AND high BHEP on low displacment engine does it have reliablity issues in the long run with that too much stress?
it's the rate at which pressure increases in the diesel that's the noisemaker, some alleviate that with 1 or 2 pre injections. Also a plastic sump to dampen noise coming out the bottom helps
Turbocharger converts part of the noise into the turbine rotation, which used to pressurize air intake (ofcourse, exhaust pressure and heat are converted too). Modern common rail injector squirts preinjection before main injection events to dampen vibration by harmonics. Also some engines actually have intake throttle, like my Chevy Captiva. While it mainly functions to maximize exhaust gas recirculation (EGR) system, it has side effect of noise reduction. Also modern heat resistant foam that is used under the engine cover and the engine hood also absorbs noise. Balance shaft is used as well to reduce vibration and therefore noise.
10:19 So I did a bit of math myself (cause I'm fun like that) and I calculated that the EMD 12-1010J, a 16.6L V12 locomotive engine with a 1 foot stroke length - which redlines at 1000 rpm - gets *_247.95 bar_* of BMEP.
So while short-stroke, high-revving engines are very efficient, the same can be said of the huge, slow, torquey engines on the other end of the scale. Just something I found interesting
The problem i have with comparing engines by their power is that we never factor in the one thing that /actually/ matters: reliability/longevity. BMEP really is showing how "high strung" an engine is.
Wow, my 2003 V6 Mustang came out with 10.1. Although who knows maybe that isn't too bad for the time. Also Go Wolfpack!
Well my 1999 e36 323i makes 12.5🙈
Don't get me wrong I also like Mustangs :)
it's terrible, murican engines always sucked at volumetric efficiency
@@einstein1984 Pretty much. But they excelled in sheer volume!
That's because you got the V6!
"Spreadsheets Heck Yeah!"
Made me laugh 😂
It would be interesting to see the value of some motorbike engine. Just for comparison.
Lucio Switch naturally aspirated:
BMW HP4 race: 15.1bar
Aprilia RSV4: 14.7bar
Kawasaki ZX10R: 14.5bar
CBR 1000rr: 14.3bar
BMW S1000rr: 14.2bar
Yamaha R1: 14.2bar
Ducati Panigale v4: 14.1bar
Supercharged:
Kawasaki H2R: 20.8bar (Boost: 1.4bar gauge) equivalent NA: 8.7bar
@@dernachtmannkommt Lets not forget the Brutale 1000rr 14.6 its a lot more comfortable to ride than superbikes ;) well until you going over 180 then you really miss having a fairing.
Usually lower but much higher rpms
Thanks@@dernachtmannkommt, so up towards the top end of the scale. But able to rev much higher than even high performance larger capacity car engines
@@AanjE I think you will miss the fairing way before 180 mph more like 100 mph
this man actually found a good use for a box and whisker plot, what a legend
I honestly don't like Math that much. I quite hate solving difficult problems. But when it comes to computing related to cars, I always get interested. I hope Jason is my Math teacher back in high school, so I wouldn't get bored of Math. But good thing that I am more interested than ever because of videos like this. Thank you Jason for making Math interesting. Hehe!
10:55 So you're saying some naturally aspirated engine make boost?
Yes, a cylinder can fill more than "100%" if the air charge has momentum or a higher than atmospheric pressure wave forcing the charge in. This is why intake and exhaust runners are tuned.
Yeah, I've been noticing for years now that when it comes to motorcycles, despite wild variations of HP/litre between different models; there isn't that much variation in terms of torque/litre, with most of them being somewhere around 9-11 kgf.m/litre (keep in mind that virtually all bikes are naturally aspirated, AFAIK the only factory non-naturally aspirated motorcycle nowadays is the supercharged Kawasaki H2/H2R).
Jason, have you ever thought of comparing engines in the form of some integration of the power curve? Of course this would require some consideration; for instance if it were integrated in terms of rpm, you would probably have to choose an arbitrary range of rpm (say the top 3000rpm with greatest power), and this would not be ideal if you were to compare between engines with significant variations of the rev limit... So I
guess it could be in terms of a certain proportion of the rev range, for instance the top 50% of the rev limit (for a 6000rpm redline, this would mean the range of 3000 rpm with greatest power). I believe something like this would give you a more significant value to compare the ability to accelerate than simply peak power.
"Non-aspirated"? Never heard it called that before, doesn't really make sense to me either. Naturally aspirated or forced, the engine is supplied with air so would therefore be aspirated.
Still playing kill zone?
Wondering where an S2000 would land, but I don’t wanna convert units lmao.
F20C: 13.1 bar, F22C1: 12.8 bar. Slight variation depending exactly which torque rating (used 153 and 162 lb-ft).
The s2000 would land in the puddle of oil the thing leaks and burns every 1k miles it runs. S2ks are great cars don't get me wrong but they are a bit heavy compared to the competition and they make power way to high in the rev range for a car that is daily driven on a regular basis. For a track car i'd buy an s2k in a heartbeat. For a daily driver i'll take a mx-5 rf so when the top isn't down I can keep the elements off of me and don't get the soft top buffeting like all the other soft top cars I've owned in the past and also when I take it easy commuting I get close to around 40mpg(38mpg was my highest and that was cruising down the highway at around 80mph).
Couldn't be bothered to work out the BMEP, but 76.5 lb/ft per liter puts it at somewhere between the Lexus LFA (73.7 lb/ft) and the Ferrari 812 (81.5 lb/ft). Not bad for an engine that was designed over 20 years ago!
@@soundseeker63 The Jag XK6 engine from the 1940's had over 70 lb/ft per litre.
IMHO, it's just an arbitrary number (like max HP), that maybe gives a little insight on the engines, but probably doesn't. It takes into account just the peak torque, but these engines have completely different torque curves and rev ranges. You can say it's the "mean", but it's just such a big shortcut, that the numbers you get in the end won't mean much. To get something more relevant, you probably could use the same math, integrate it through the whole torque curve, and divide it by the rev range. It would reflect much better the effective pressure.
Excellent content and beautiful explanation! Loved it.
Great stuff, In the early 80s I began to wonder why porsche and jaguar engines of less than 3.5 litres were putting out more power than 5+ litre V8 engines. It was then that I learned of volumetric efficiency. Great explanation - will do calcs for my daily driver.
As a mechanical engineer, this is Porn🤤
Switched my major right from M.E. right before thermodynamics class... however this is still porn 💀💀💀🔥🔥🔥
I found a new record for lowest BMAP. the 1996-2006 jeep wranglers (and other models) had a 4L inline 6 making 190hp and 225 ftlbs. The BMEP comes out to 9.5 lol. This is actually really surprising to me considering its one of very few gas engines that make quite a bit more torque than hp.
I'm sceptic about all of this, in a constructive way, its nonsense.
how do you cancel out the RPS at step 9? the crankshaft and the wheels do not spin at the same ratio, at least you must've explained the particular case of using the 1:1 gear ratio of the gearbox.
Then you are making another big mistake, that is to take the torque at the crankshaft, because in step 7 you cancelled out the radius, and if you assume they are the same, you are using the torque at the wheels. Otherwise you'll be taking the crank radius equal to the wheel radius.
Cool video anyway, keep it up
Power is made by the engine not anything else. The rest (gearbox, clutches, axles etc) is just transmitting the power.
Hi. Torque is measured at the crankshaft. Rps does not count because is the speed of the crankshaft. Transmission does not count in this calculation.
Measured at the flywheel, not the wheels,
A better way of thinking about this is that it an engine with a higher BMEP with more efficiently exert a pressure throughout its entire stroke. Doing so is very nontrivial and means that the intake, exhause, engine balance, etc. etc. have all been thoughtfully engineered. The engine will have to make maximal use of the power stroke, have minimal losses during the exhuast and intake strokes, and be mechanically perfect enough to not dissipate energy in vibrations and heat.
On a side note, the way Jason does units is maddening to me as a physicist XD.
I used to operate 18 cylinder, 2800 cubic inch, supercharged aircraft engines, with water-injection for detonation prevention at very high [power settings (2400 HP, using 100 octane fuel.). Although we used Manifold Pressure & Engine RPM as our primary power-setting guidance, each engine also had a nice BMEP (that's "Bee Emm Eee Pee", *NOT* "BeeMep") guage at the top of it's stack, calibrated in Pounds per Square Inch, Mercury. We used this data to precisely set our cruise fuel mixture ratio, as well as monitor overall engine power output. If we wanted to figure out actual HorsePower being developed, we simply multiplied BMEP by Engine RPM, and then divided the product by the mathematical constant "283". As an example, in a high-power cruise you might read a BMEP of 140 @ 2400 RPM. This gave you about 1200 HP Cruise power. I have no idea where the "283" was derived from, but it just always worked for our calculations.
I don't think rolls is embarrassed about their engines...
Maybe they should be, but perhaps rich folk are impressed by throwing displacement or boost at engines instead of good engineering. As long as they sell big comfy cars I guess.
@@CompTechs for the rich folks,, bigger=better, more expensive etc..
@@CompTechs There's plenty of great engineering in that engine.
You can make an engine with massive BMEP by simply lowering the hell out of compression ratio, fitting a massive turbo and intercooler and cranking up the boost until just before it blows up. Doesn't make it a particularly impressive feat of engineering.
When the metric you're using to measure the quality of an engine gives you results that say an MX-5 is as good as an LFA that's a pretty big giveaway that that metric by itself isn't particularly useful or relevant.
@@CompTechs damn, people like you know nothing about cars... Rolls royce couldn't care less about a performance Stat such as BMEP, since their cars have a completely different purpose.
The engine needs to be silent, robust and definetely not high performing (good acceleration is not important in such car). The rolls royce is perfect in that case so stop mixing up stuff you know nothing about.
It's like saying "F1 cars are slow because they have low torque". You guys Completely missed the point.
Perhaps the greatest sports car of all time xD
Without telling WHICH, does make it a pointless comment... 🥴
@@eknaap8800 He's referencing the comment in the video. MX-5, obv!
That would be the one vehicle that I haven't designed yet. It would incorporate my anti-knock engine technology, among other things.
Somehow feel like this needs a mentioning of a Honda K20 somewhere ;)
K20 makes about 100Nm/ liter if I'm not mistaken, with the Mugen FD2 Type-R being the most impressive at 110Nm/ liter and it maintained that number until peak power.
The BMEP thing just translates to Nm/liter, and the maximum potential for N/A motors is about 120Nm/ liter and 105-110Nm/ liter at peak power.
So refreshing to see sums without any calculus. makes it so much easier to understand.
Respect to you Jason, you take the craziest concepts and explain them really well. I think maybe it’s a gift. I had a philosophy professor in college who had the same gift. Others could talk The Who semester and it made no sense. Not here. This video was SO interesting. I hope you consider applying to other types of engines. Cool.
"I was told there would be no math!"
It breaks the scale . ...That I made up 😂
So I'm about 5 minutes into the video. Is this basically another form of a way to say power per liter?
Edit: got to 6:30 and wow, I surprised myself that I was right. My mama said I was smart.
6:40- They'll walk away from you
9:35- It breaks the scale, that I made up 😂😂 😂😂 Jason funny AF
Minute 6:45 is how my wife feels every time I start talking about cars. Love the videos, keep 'em coming!
Nicely done -- and long overdue. Too much focus on horsepower and too little awareness of torque (and BMEP) as what most matters. Touche.
Is clear that you have no idea what you are taking about. Torque and power are in a direct relationship, so simplistically speaking they tell us the same thing. What really matters and people are not aware is that all manufactures specify only peak power/torque and what is actually important is power/torque curve over the nominal RPM range of the engine.
Torque is what people feel when leaving stop sign. And, people feel that many times when they drive. Peak horsepower (or peak torque) is rarely felt, if ever, in normal use. Let's keep the comments respectful.
No mention of Wankel engines? Missed opportunity!
Problem is, no one knows the formula for the area of a Dorito. It's kind of like the English word that rhymes with orange. We're not tryna create any blackholes here.
@@bradleyland you'd have to divide by zero.
Hmmm there must be a way to figure it out, technically distance traveled would be 1 rotation right? And you can get the surface area of the face, also I'm not sure how many times it fires throughout that rotation though
Did the math. You gotta use the 2 stroke equation and it comes out to BMEP= 10.4 Bar for the Renesis. Lower is better right?
Question. How could one apply this to Wankel rotary engines?
You'd multiply by a ratio. I don't remember the exacts of the wankel design. Is it three burns per revolution and two engine revolution equals one crankshaft revolution?
Basically, get a ratio that removes the differences in power delivery.
My ‘06 Acura TL has a stock, naturally aspirated SOHC 3.2L V6 equipped with a variable volume induction (VVI) intake manifold setup that utilizes the ‘Helmholtz Resonance Effect’ to introduce a mild supercharged intake boost for improved induction efficiency. This effect is essentially the same as how (tuned) engine exhaust headers work. They apply a pulse or tuned scavenging effect that sort of sucks the exhaust gas out improving flow efficiency with accompanying increase in power. All to say cars employing the gimmick of a VVI, naturally aspirated intake increase charge efficiencies w/o the use of a turbo of a supercharger.
So, basically I need a bigger turbo and bigger exhaust pipe on my Volvo T6 engine 😊
Time to go Diesel.
Lactose intolerance causes a lot of mean effective pressure.
You meen Gross effective pressure ?