Why It’s Almost Impossible to Rev to 21,000 RPM

[@bythelee]

NONE of the thermal or stress issues are a deal breaker. Having worked in F1, analysing stresses in pistons and conrods and crankshafts and valves, I'm quite sure everything could easily run much faster - 30,000rpm would be no problem, particularly if exotic materials are allowed (like aluminium - beryllium). Turbochargers in humble road cars can hit 100k rpm while red hot... The killer factor is time. Higher RPM means less time per cycle, but the physics of fuel combustion are "fixed", in that flame fronts take finite time to propagate. The flame-shooting injection is a great idea - an advance on Alfa Romeo's "Twinspark" idea that used two spark plugs to start two flame fronts in the combustion chamber. The second problem is keeping everything synchronised. While the components can be designed to survive the loads and stresses, keeping the valve timing synchronised with the piston motion is harder than it might seem. (Quite apart from the problem of "when to start combustion" to get an optimal power output from the cylinder (fire too early, combustion works against you. Fire too late, most of the power goes out the exhaust. Ignition advance is a huge field all to itself. But I digress.) Because, nothing is rigid, and everything is flexible. And twistable. V12s and V16s have much longer crankshafts and camshafts, and will twist along their length, resulting in some very serious timing errors in the cylinders remote from where the shafts are linked together. Various efforts to deal with this include using link gears at both ends of the engine, or putting them in the middle. Which brings their own problems with "forced" positional control, that can induce their own breaking loads. This can all be engineered around, not least via novel valve technologies. But to even be aware that everything is flexible, and avoid the typical "rigid body" thinking that seemed to afflict everyone else working in the field, is a challenge in itself. For those that doubt if I know what I'm talking about, take a closer look at the bending crankshaft animation at 8:03. That is NOT showing "stress" (so, we don't even have to debate whether it is Maximum Principle Stress, or Von Mises stress, or some value of fatigue alternating stress - ALL of which MIGHT be the one dominating "failure".) It is showing a colour contour map of DISPLACEMENT. Because, the entire "red" part of the crank does NOT have similar stress - that would be concentrated at the fillet between crank web and big end... certainly not distributed equally over the whole section. Worse than that, the deformation is created by moving the centre main bearing while holding the mains at each end - a totally false load case that simply never happens in reality. At least, not to the extent it is shown here. Some movement is possible because these bearings are oil film (journal) bearings, and the oil film thickness allows a small amount of movement. But this animation is not intended to show that, since displacement at the centre WOULD cause movement in the end bearings too - the crankshaft stiffness forces that. One of the reasons I gave up doing what I did, was the disparaging remarks about being "the pretty pictures department" by folk that did not bother to look at my track record of "ZERO in-service failure" of any part I ever worked on. Sigh. But sadly, even 20 years later in 2024, it seems not only has nothing changed, but the "pretty picture" is not even a valid picture at all, but something created purely to look pretty. Sigh. TMI but for those still interested, "zero in-service failure" means inifinite life while in use in the engine. NOT "unbreakable parts" (you just have to subject them to loads they never see in service, to get them to break). This included redesigning finger followers that broke in 10 minutes, and conrods that snapped in an hour. All of these became "infinite life" parts that could last forever, just by fettling design details. And, making them lighter for better performance at the same time. For me, durability usually meant removing redundant material, and sometimes redistributing material, to better disperse loads (and hence stresses) throughout the structure. I never had to fix anything by adding any material to it. Which is contrary to intuition, and is the "go-to" response of about 99% of others doing this kind of work. "Beef up the weak bit" is NOT a good thing to hear. Just like the crankshaft that drew envy because it NEVER broke, not only lasting an entire race season, but also having the smallest main bearings of any crankshaft on the racetrack. (and smaller mains meant less parasitic torque was drained from the power output, giving more BHP at the flywheel...) But smaller bearings mean a huge increase in stress concentration, making it much more difficult to endure the loads any crankshaft has to survive. Anybody else that even tried to match our bearing size, never finished one race. When you get a handle on engineering, and materials, and stresses and strains, and loads, and resonance, and vibration, and heat transfer and temperatures, and... then designing engine parts for conditions thought impossible, becomes quite possible. There certainly are limits. Yield strengths of materials, for one. And when you factor in that the strength depends on temperature, too... But rather than get sidetracked further on "strain rate sensivity" and why F1 pistons survive stresses more than four times higher than their yield strength at operational temperature, just know that we are still quite far from reaching those boundaries with designs at 20k rpm. I mean, 99% of the piston is not even close to failure. It is the 1% detail problem where stresses concentrate that start the cracks that lead to failure. Same with that crankshaft. The challenge is fettling the details WHERE THEY MATTER. Sorry for the essay. Thanks for reading.

[@estebannegrete7662]

Thanks for the writing. Fellow mechanical engineer here... one that knows why adding material to the most stressed point of a part doesn't work ;)

[@tomvoorhis7541]

Thanks for the essay. I appreciate the insight.

[@David_Crayford]

Thank you for your insight. It appears we not only have to deal with stress on engines - but also the stress on engineers!

[@Hoch134]

Thank you for your essay. I'm not an engineer but I really enjoyed reading it.

[@tomast9034]

at the end its the same as with the diesel engines cant do more as 8000 rpm due to mixture burn time. maybe going with detonation burning? :D

[@lenmetallica]

The fact that this video is still live after all the inaccuracies and wrong information speaks louder than the mistakes themselves.

[@merkatorix]

I didn't even reach 15 seconds. Usually, I am sloppy myself, and it might be a minor thing, but I wonder how the piston can change its mass to 2.5 tonnes. Of course, I would also say that my weight changes at the moon, but that sentence sounds too wrong to count as colloquial. Maybe my 8th-grade Physics teacher trained me enough. But even before, I would have said that my weight changes, not my mass.

[@Brushyip]

I didint realize it was misinformation untill I was halfway into the video. I feel so dumb bruh

[@merkatorix]

​@@Brushyip I can understand. It's KZbin, and you are here to relax and not to concentrate on details. Maybe, I wouldn't roast him too much, too, although I stopped watching the video, and decided he might be not the right channel for me. Many KZbinrs are sometimes sloppy, and to a degree the algorithm forces them to have high throughput. In the end, its not a physics channel and short headlines always sound good. Watching it, is like reading an article of the rainbow press and noticing halfway through the article, it's not a reliable source ^^. I guess, usually the channel is not that bad, though.

[@jamiecloughgaming25387]

@@merkatorix Don't be too hard on Scott Mansell he's not an engineer, he's a former racing driver.

[@merkatorix]

@@jamiecloughgaming25387 I agree, and he probably does a good job. I just think, I'm not his target audience. I like the history summaries of Aidan Millward, I think, but mostly, I'm the target audience of engineers. I also agree, that it might have been better to not write that, because it probably sounds too negative. If you want a job in F1 and racing, I don't know, if there is a better channel.

[@TheNecromancer6666]

The main reasons are actually the speed of the flamewall starts to be too slow, the combination of high compression and ultrashort stroke reaches mechanical limits, and the extremely narrow gap between head and piston at TDC prevents a clean burn. The mechanical load is a problem that is solvable.

[@Colby_0-3_IRL_and_title_fights]

Yep deflagration is too slow of a combustion method at this point. Detonation could help if an internal combustion engine could make it work like a pulse detonation or rotating detonation engine in aerospace.

[@qasimmir7117]

Yes, absolutely correct. There is a thermodynamic limit to how fast the fuel mixture can burn and expand.

[@brynfisher8019]

Honda did 22500 in the 60s with the rc116. Try again

[@TheNecromancer6666]

@@brynfisher8019 Read what I wrote again. And then you can answer for yourself why the RC116 might have just worked. While the 300cc cylinder of an F1 V8 or V10 would not.

[@chitlitlah]

@@brynfisher8019 Formula 1 engines are much larger than 50 cc. Try again.

[@Prelude610]

The video never actually answered the question. It pointed out the difficulties of running at 20,000 rpm, but did not actually tell us why it could not go higher.

[@procatprocat9647]

That's because it isn't a real limit. - You could make the pistons smaller to reduce their mass. - Materials science is constantly developing. - So are design analysis techniques.

[@rednezz]

Velocity and size of charge of the air fuel mixture can also limit how high the rpm can go. I had always heard they couldn’t go beyond 20k rpm because they couldn’t get the air fuel mixture in the chamber any faster. I had heard at 20k rpm they couldn’t over come the pressure wave the intake generated to go beyond that limit.

[@brynfisher8019]

​@@rednezzHonda did 22500 in the 60s with the rc116

[@rednezz]

@@brynfisher8019 Yes, for sure. I was just stating the 20k limit for the formula one engines was not due to G forces but more due to intake limitations. I am sure without any rules that put boundaries on the engine, intake and exhaust design those F1 V10’s would surpass 20k rpm.

[@J_G_G_R]

The answer is still regulations. You still have things like budget, fuel flow limit, reliability, etc.

[@katchF22]

Mass doesn't change with velocity, the piston doesn't magically become 2.5 tons. If you're talking engineering you absolutely have to be precise with your terms, man

[@justaperson3119]

Technically, mass does change with speed, but not by much

[@christophersilver1902]

It's still sorta accurate, tons is a weight which is a force not a mass.

[@Parc_Ferme]

Are you asking too much, they use Imperial to talk about a sport that is metric standard.

[@bowez9]

Short ton, long tonne or metric ton?

[@mdb4879]

He's not explaining things for engineers to understand. He's explaining things for the layman to understand. No need to be pedantic.

[@jimpartridge9634]

I remember being under the grandstand during USGP practice when Williams was very nearly 21,000 rpm. What a thrilling sound. Menacing, spine chilling, and the Mercedes McLaren engine still sounded more violent than the rest. Miss those V10s

[@benjaminshropshire2900]

An interesting side note: it's not uncommon for the massive diesel engines on cargo ships to be 2-cycle, but that's at least in part because they run slow enough to be able to effectively replace the exhaust with fresh air via blowers (which they have the room for) and that also allows them to not run oil mixed with the fuel (which might not be as big a deal given the fuel they run isn't that much different in weight than motor oil).

[@reetspetit]

Also means you can run them in reverse easily so can dispense with a gearbox. I digress....

[@filipruml]

In weight? What does that mean?

[@reetspetit]

@@filipruml think they're referring to the viscosity of the oil. They used to run "better"/lighter grade for manouvering for better stop/start/response and then something almost akin to tar for once at sea and full speed.

[@lucasandri5462]

They're also very efficient

[@benjaminshropshire2900]

​ @filipruml e.g. "30 weight" oil is a common motor oil. It mostly refers to viscosity.

[@dr.hugog.hackenbush9443]

The only problem is that they DID 20K rpm... It CAN be done. Honda had a roadrace bike that would rev to 22K rom in the '60s.

[@Noise-Bomb]

yes, as stated in the video but never 21000 RPM

[@AndrewTSq]

@@Noise-Bomb but if it went to 22k rpm, I am sure it must have been doing 21 on the way up...

[@SimonBauer7]

thing is the bike pistons are smaller and lighter, so higher rpm is possible.

[@hugo.thefrenchie]

@@AndrewTSq a bike engine went to 22K, NOT an F1 engine as was specified

[@bobbobert9379]

​@@AndrewTSq nope, according to this video there's a discontinuity in the graph at 21000 and no where else

[@mitchellsteindler]

You made it out to seem that there was a reason that specifically 20,000 rpm is the limit.

[@Lobo-tommy10]

Right? Like a sound barrier.

[@deadprivacy]

All of things in the video create that barrier. Taken to the limits across the board , its the rev speed where you cant get any higher. Driving something at speed with a reciprocating mass tops out around there. You can goi a little faster with a rotary engine but heat soak becomes a big issue and your limited ti around 20000 for anything resembling reliability.

[@mitchellsteindler]

@@deadprivacy no they dont

[@dalyxia]

Short answer: mechanical stress

[@AndrewTSq]

but we had 2 strokes rev higher?

[@kmanrox]

Thank you

[@Raziel1984]

short simple answer: to much "brrrrrrrrt" engine goes "boooom"

[@mandrakejake]

@@AndrewTSq a common misconception. 2 strokes sound faster but typically rev less. Honda's RC116 50cc 4-stroke (from 1966!) can rev to 21.5kRPM.

[@mrmedium7984]

@@AndrewTSq 2 strokes traveled half the distance before combustion

[@TheHypnotstCollector]

F1 engines were touching 22,000rpm in c.2006. Saw it on TV. The tach touched 22K from time to time,

[@JTTTTT850]

Same idk why the media acts like it never happened.

[@geniferteal4178]

​@JTTTTT850 thanks. I was wondering this.

[@chuckschillingvideos]

Was that under acceleration or because of downshifts? I don't remember seeing 22k engines at the time.

[@TheHypnotstCollector]

@@chuckschillingvideos They were Reving and Shifting. Vrooom. Find some F1 races from the time, the sound alone is therapeutic....

[@chuckschillingvideos]

@@TheHypnotstCollector Oh, I know all too well what F1 once sounded like and what they abandoned. I was just never a tach watcher back in the day. Don't know what you've got till its gone, right?

[@thedirtyworkshop]

Is this a challenge on how to get as many details wrong as possible in 13 minutes?

[@davidg3944]

Ooh, -burn-...

[@V8Lenny]

Do you think he can win you ?

[@billymanilli]

@@V8Lenny I don't think Matt swings that way, bro...

[@V8Lenny]

@@billymanilli he just removes his BS videos after proven being wrong.

[@thekinginyellow1744]

0:10 Mass of... Beg pardon? You need to look up the definition of mass. I'll give you a hint, acceleration doesn't change it.

[@MrAdopado]

You are right of course ... but in a speedy presentation intended for mere mortals you often get these detail errors. If he had used some wording similar to "a force equivalent to pulling and pushing x tons" perhaps we could live with it ... we are not all familiar with talking Newtons!

[@thekinginyellow1744]

@@MrAdopado Because it matters. By not using correct terms, you propagate incorrect ones.

[@finestructureconstant3921]

Correct. Mass is defined as the resistance an object offers to changes in its motion when a force is applied, known as inertia

[@syntropy3020]

Frame front velocity of the fuel is what determines rpm limit. Different fuels have different flame front velocities, and thus different rpm limits for the same engine.

[@pjlangford1959]

My little Honda CBR250RR will rev to 21,000, it's stopped making power at 19,000 but I've seen it as high as 23,000 on the track. And that's 1990 technology and it's still going strong.

[@TheSnivilous]

15 seconds in and you're killing me. Mass isn't changing, force is changing. There's no extra "stuff" just because it's accelerating so quickly.

[@Colby_0-3_IRL_and_title_fights]

The faster Usain Bolt runs, the more obese he becomes

[@jasonsmith4902]

He was referring to inertial load on the connecting rod, effective weight of the piston when changing directions. He is most surely reading a script which was poorly written to exclude this detail.

[@ericpedigo685]

What he was referring to was the amount of force being exerted on the crankshaft and the connecting rods due to acceleration of the piston,The higher your acceleration, all of that momentum needs to return and go the opposite direction so what you run into is more RPM means more additional stored energy via momentum, compare it to locking up the brakes on a car at 60 miles an hour versus 120 miles an hour, or falling down on the ground vs a 10 story building

[@xxStealthHunterx]

@@ericpedigo685 yeah but it's not "mass"

[@billymanilli]

@@Colby_0-3_IRL_and_title_fights that literally made me lmfao. Thanks! 🤣👍

[@KaDuWin]

Renault and BMW both managed 21k in the V10 era of F1 before the FIA issued an order limiting engine RPMs to 19k.

[@xrand0mx]

My first bike was a 1987 Yamaha FZR250R. It had a 19k recline and while not particularly fast, it was absolutely glorious. F1 sounds at reasonable speeds. I miss the simplicity of youth.

[@devilsoffspring5519]

Nothing says you can't ride a 'screamer' motorbike when you're old too, just try not to croak on it!

[@y_fam_goeglyd]

When you explained the actions of the four stroke I was taken back many years, to when I started work at a Ford engine plant (I was 17. God that was so long ago!). My dad explained it using the "suck, squeeze, bang, blow" saying. It really helped me visualise it. And as you went from one part to the next, I was hearing those words in my mind just before you used the more technical ones 😂 Fascinating stuff!

[@JohnJohn-zh4ov]

A couple of things that I noticed in the video. Engine friction wasn't mentioned but is a key reason for not increasing engine speed further. The NA F1 engines used port-fuel injection, direct injection came along in 2014. Current F1 engines do not use TJI as described in the video, they use a passive pre-chamber as only one injector per cylinder is allowed. The stoichiometric air-fuel ratio of gasoline isn't 14.7:1, it depends the formulation of the particular fuel.

[@thedirtyworkshop]

"The stoichiometric air-fuel ratio of gasoline isn't 14.7:1" - Generally speaking is it.

[@JohnJohn-zh4ov]

@@thedirtyworkshop generally speaking it's not, which is why most people would use lambda or equivalence ratio to describe the chemistry of the air-fuel mixture, as it's formulation agnostic.

[@spacecadet35]

To quote von Braun "I have become very careful about using the word 'Impossible'."

[@tomast9034]

@@spacecadet35 there is always at least one who can do it.

[@grantfuller2016]

The more power strokes you can squeeze into a minute,( rpm ) the more power you make -But - the volumetric efficiency gets worse as you try to speed things up ( that whole getting the air and fuel into the cylinder and mixed , thing ) . There’s a point at which at which the gains by higher rpm get overtaken by the loss in volumetric efficiency . Had a tutor who said “ at 20,000 rpm pistons don’t go up and down - they just vibrate “ 😂

[@Impeller_GR]

6:25 Massive blunder here, con-rod length does not influence stroke and therefore the bore/stroke ratio and engine „squareness“, only the crank can influence stroke. Rod length to stroke ratio is a whole other matter.

[@rickmental1767]

Thanks!

[@bryce1916]

I find it kind of funny that they just created prechamber ignition for F1 even though this is ancient diesel technology where early Cat diesel engines used precups or Pre-combustion chambers that would start the burn before entering the cylinder .

[@peterfisher2586]

I’m fairly certain that Honda had an engine revving to 22000 rpm in the early 60s. They didn’t believe the riders claim of 22k rpm but then took it home and ran it for an hour at 22k

[@pauldonnelly7949]

No mention of the Honda air cooled, conventional valve springs, sixes of their racing bikes in the 60's, that routinely reved to 23k rpm? Relevant as they won at least 2 world championships and remained reliable. Also no mention of the, again Honda, CVICC system of the 70's? Strange because it is exactly the system you describe as new in 2015...

[@Paul58069]

it was actually the CVCC system :), but I was thinking the same !

[@MrAdopado]

That only works because of the smaller size/capacity. There are lots of engines that can rev way more than 20k ... they are in model aeroplanes. This is because they are very small. By the time you get up to the sizes needed for an F1 engine you are reaching the limits.

[@jasonsmith4902]

@@MrAdopado This destroys the argument about thermodynamic limits of combustion they were having above doesn't it?

[@MrAdopado]

@@jasonsmith4902 There is a limit of combustion ... the speed of the flame front is fixed so though it has time to zip across a small combustion chamber it doesn't have time to completely fill a large combustion chamber so only a partial burn is achieved and efficiency is lost. That's why it's possible in small engines but not in engines of the size needed for Formula One.

[@gbreslin6635]

Yes, Japanese bike engines have always been far ahead of car engines. Car manufacturers have always gone for image, no matter what the image.

[@therealchayd]

Internal combustion piston engines are just insane, I mean 20,000 rpm means each piston is changing direction 666.6 times *EVERY SECOND* (at BDC and TDC, i.e. twice per rotation). Pretty mind-boggling.

[@henriklmao]

That's pretty satanic, I'm not going above 19.990 then 😂

[@therealchayd]

@@henriklmao Yeah, I really should've rounded up 🤣

[@tomast9034]

@@henriklmao nothing beats the devil🤣🤣 not even f1 engines.

[@MrOiram46]

@@henriklmaoJust rev up to 21K 😂

[@OptiVR]

Because they don't want or need to. Everything about F1 is rules and limitations, if they had to rev to 21000, they'd figure it out. ( and we'd probably see some new rotary designs because pistons are horrifically inefficient when scaled with speed, because the reciprocating load scales with revs )

[@c-ro311]

Problem is that rotaries, due to low compression ratios, massive conbustion chambers, are terribly inefficient, which is the opposite direction the FIA wants for F1

[@TheOfficialOriginalChad]

Exactly. Physics wouldn’t apply if the rules required them not to. We would have faster than light travel now too if the FIA made it a rule.

[@chuckschillingvideos]

@@c-ro311That's precisely the problem. The clowns dictating the technical parameters are, in the depths of their evil black hearts, accountants and politicians.

[@wiegraf9009]

Real galaxy brain take here

[@c-ro311]

@@chuckschillingvideos nah they aren't clowns: almost any numbskull can make a 1000 hp engine, making them efficient at the same time is what advances technology

[@roeloftooms]

Our small 3.5cc model competition engines are 2 stroke and are able to run 48.000 rpm on the track and w/o load they can shoot over 50.000 rpm.

[@bl4ckscor3]

3:55 ah yes, rice.

[@kalebbruwer]

Yeah, doesn't really work when rotary ICE engines also abbreviate to rice...

[@crazyredhare]

I did some ball park math years ago. A high reving engine, the piston can travel up to 80 MPH. Fairly impressive, but it changes direction (up-down) about 500 times PER SECOND.

[@georgedreisch2662]

How about a episode on F-1 pre-chamber ignition? Possibly, Micah McMahan as a resource?

[@marckart66]

I remember back when I was kart racing. I started off with 100cc karts but I never raced them. While racing with TKM and Rotax engines, I always had older 100cc engines laying about. I remember my Vortex VR / CW rotary valved engine. That engine would SCREAM. Highest I ever had it was 23,000rpm. Although I never raced it. Occasionally I'd stick on a larger rear sprocket on the colder dry days and let it sing. You really seen the temp go up. If I managed 5 laps in a row achieving 22k rpm, water temp would easily go over 70c and you'd struggle getting 20k. It was all about managing the carb and temp. Leaner engine, more power, more temp. On the really hot days I kept it rich but it was still achieving 18k to 20k. Really loved those days... I miss the smell and noise.

[@philologusopin47us57]

Ive never learnt so much about engines before. Your Videos are awesome.

[@JeffSyam]

Thanks for making this video. Many times people blaming MGU for less screaming on current PU, whereas it's actually it's rev/minutes, as current PU rarely reach 13000 rpm.

[@MangoIsLove55]

2:04 wait what?

[@jamesmonschke747]

Questions: 1) If the pre-chamber ignition is causing the main chamber to ignite in more locations, that sounds analogous to pre-ignition which normally could cause detonation in a (normal) engine. Why doesn't that occur in this case? 2) In a 4-cycle engine, the connecting rod is in tension during the "suck" cycle of the 4-cycle engine, but in the 2-cycle engine, the rods are always in compression and never in tension. I wonder if that may be one more factor in the 2-cycle engine being able to reach higher RPMs (i.e. if the connecting rods might be weaker in tension when accelerating the piston downward for air/fuel intake)?

[@jowarrior]

Time for f1 to move to Rotary engines.

[@nidhisingla7880]

That would be wild and stupid

[@jowarrior]

@@nidhisingla7880 as with most interesting things in life.

[@henryhallam5270]

@@jowarriorAs much as I want to agree with you, adding rotary engines would be the worst f1 regulation of all time.

[@jowarrior]

@@henryhallam5270 I’m not saying to force Rotary engines, just allowing them to the engine options.

[@henryhallam5270]

@@jowarrior But it would be pointless then because nobody would use them 🤷‍♂️

[@B_dev]

wow, that prechamber ignition is genious! so elegant!

[@Onewolfoc]

The part at about 5:21 - 5:31 is incredibly painful. 2 strokes do not have to burn the oil that is used for lubricant any more than any other piston or rotary internal combustion does. In fact whats even more painful about this is the animation there shows a engine with a blower similar to the 2 stroke detroit diesels. (this particular design does not burn the oil) Not to mention the so claimed emissions and reliability concerns with burning the oil simply are mostly inaccurate or straight up incorrect depending on what part your talking about. Burning premixed gas and oil is bad for emissions compliance yes. However all emissions control systems already in service for modern engines would work with 2 strokes like the detroit diesel's there are pleanty of 2 stroke engine designs going back to 1872 that have no need to premix oil and fuel. To be clear thats 19 years after the first true internal combustion engine. 2 strokes are only 19 years from the oldest of internal combustion engine designs and a good portion of those designs as I said have absolutely no need for premixed fuel and can completely be used with hydraulic bearing aseemblies and effectively sealed crankcases.These engines overcome the crank case pressuization issue that needs to happen to force a new charge up into the cylinder by using forced induction namely often a blower (aka supercharger and this is where your popular superchargers came from earlier in drag racing many of them were off of 2 stroke detroit diesels then adapted for use on 4 stroke v8s.) thats where the production numbers became high enough to make them fairly affordable. (Relatively speaking) In these systems the crank case is nearly sealed and you end up typical running a hydraulic bearing assembly. The freah charge air is forced in with the forced induction system and the fuel can be added either by a carb or via a injector and it can either be direct injection or common rail or even just injected into the intake. You only need the blower to produce a few PSI of positive pressure to overcome the force of the residual pressure from residual exhaust gases. In more simplistic 2 strokes like many but not all marine 2 strokes. Dirt bikes , weed wackers , chain saws , motorcycles , ect they pressurize the crankcase with a valve that opens and closes which forced the fresh fuel air charge up into the cylinder. Typically a reed valve but can also be a rotary valve. This is only done on the most simplistic engine designs or ones where mixing fuel and oil is not a concern. Its not even new tech to use a forced induction system and a hydraulic bearing assembly in a 2 stroke engine been done for more than 70 years now along with the other style of NA 2 strokes without it. Actually in addition there have been some engine designs to use a "dead" cylinder to act as a forced induction system to pull off this same effect. Some of these designs are nearly as old as the internal combustion engine. The only issue inherent in a 2 stroke design that has not been completely solved and is sort of a function of the design is their natural somewhat asthmatic transition between combustion and intake where your trying to get the exhaust out and a new change into a cylinder that is a bit above atmospheric pressure. Hence the need to provide some form of forced induction. We have full direct injection systems, port tuning/timing systems , we can go full hydraulic bearing and have for more then 70 years (thats very old tech) we just dont see all of these features on modern engines (some you do like direct injection but its still used on simplistic engine designs with a pressurized crank case) its simply cost and complacency within the companies that still use them. If the numbers of small supercharger assmebles were increased the cost would drop and make it more common to see. Im not saying 2 strokes are inherently the best for all things. Just that this information is really BAD at the above timestamps and not only is incorrect it is also confusing cause he says 2 strokes have to burn their own lubricant while showing the diagram that is pretty much a 2 stroke detroit diesel. This is a system that doesn't do that. We have much much much older designs as well that also do not have to premix that go back to nearly the dawn of internal combustion motors. (1872 here) And the early internal combustion engine came out of 1853. Talking 19 years later here. I do not even have the time or space here to get jnto the incorrect info about reliability or lifespan that was also mentioned in the video. There are 2 stroke engines still in service that are substantially older than many of the adults watching this video. You can optimize a engine for many things. Its a bad assumption to think what makes a cheap 2 stroke weed eater not all that special or relaible then apply that to the entire 2 stroke engine design philosophy. It is simply incorrect ...yet more bad info in this video. Infact i have mutiple 2 stroke motors that have been in service since the early 1950s and never have had a major mechancial overhaul and that even includes the detrimental effects to the engines with the modern e10 and e15 fuels. I have a 4 cylinder powerhead from 1960 and a twin from the early 50s still in service that have a lot of life left in them and are older than most of the people watching this. There is nothing we do with 2 strokes that cannot also be done with a 2 stroke outside of the limiations with around forcing new air and fuel charge into the cylinder. That only takes some form of low pressure forced induction. Talking few psi at most. Blower / supercharger , turbo , dead cylinder , pressurized crankcase , hydraulic bearings , emissions systems like Catalytic converters , 02 sensors , direct injection, common rail or multipoint fuel injection, variable timing / variable port timing and even EGR can be used with them. Depending on how you want to optimize the engine. The only significant difference between the technologies that make up 2 and 4 strokes is the design philosophy around intake and exhaust cycles. Fudimentially almost all of the other tech is shared or can work on the other with the right design.

[@tomoliver5861]

Driver 61 has such good production quality for being so wrong

[@FredsRandomFinds]

Surprised no one has tried an engine with Oval Pistons like Honda did with the NR500/750 8v per cylinder and two conrods per piston?

[@GordonMoat]

Think you mean the NR500 race bike, which revved close to 20000rpm. There was a brief oval piston 750 version, which I think raced (unsuccessfully) at the Suzuka 8 Hours. The later NR750 oval (square) road bike didn’t rev that high like the original racer, but way more reliable.

[@martinhow121]

@@GordonMoat The Oval pistons were to increase the valve area on a naturally aspirated engine. It's of no advantage and lots of disadvantages on a turbo charged engine. In particular uneven piston ring wear and expansion and uneven burning due to the asymmetric shape of the combustion chamber.

[@GordonMoat]

@@martinhow121 Honda gained some unique parents on piston rings from those engines. They've applied some of that knowledge to later conventional round pistons rings, to improve sealing and lesson friction. In motorcycle racing, what they were trying to do was make a V8 under rules that only allowed four cylinders. Of course, the engine wasn't the only issue on those racebikes.

[@peterstim44]

In the 90's Honda developed an oval piston 4 stroke NR500 engine which rev'd over 22000 RPM. Expensive to run and build. Honda estimated an oval piston could achieve 23000 rpm before it exceeded burn/flame out.

[@ObnoxiusBrat]

Meanwhile engineers: hold my beer I bet they could do impossible, if they had a chance

[@procatprocat9647]

We definitely could !

[@Laylander]

Without regulation only the laws of physics remain. And we know physics very well. I think every car would become a torbine car simply due to the power/weight advantage.

[@procatprocat9647]

@@Laylander ​@Laylander turbines are terrible at rpm changes. A turbine powering a generator for electric motors is a realistic option. The battery or supercapacitor could be very small as it would only be needed to fill time when the turbine is speeding up

[@caprinicus8268]

I rarely post comments like this but... At 8:18 - Aluminum has a better strength to weight ratio than steel, but is more vulnerable to fatigue, not less. Strength and weight are completely unrelated to fatigue in general. You actually picked the two most extreme examples to be wrong about - in that some steels will literally never fail due to fatigue as long as they aren't overloaded, but with aluminum any repeated load will eventually cause a fatigue failure no matter how small. Some ferrous titanium alloys can behave more like steel - but it's because they're ferrous, not because they're titanium.

[@razinkhan6750]

The dislikes are from the pistons harmed in the making of this video

[@jamesoshea580]

Or people that dislike inaccuracies...

[@rori8790]

Honda 50 cc twin cilnder racing engine and the 125cc 5 cilinder were able to run at 35000 rpm in tests in races at around 30.000 max this in 1967

[@DaveMcIroy]

Nope. BMW once did 21,005RPM.

[@ObnoxiusBrat]

And then exploded

[@DaveMcIroy]

@@ObnoxiusBrat, don't think so.

[@Flying_Fetus]

Meanwhile yo mamma hitting 22,069 rpm

[@DaveMcIroy]

​@@Flying_Fetus, you mean 42069.

[@jstogdill]

ICE are fundamentally air pumps that you squirt fuel into. For a given displacement higher rpm means more air flow and more capacity to burn fuel. They are limited by mechanical loads and flame speed. At very high rpm both of those factors come into play even for very oversquare engines. Two strokes move something approaching twice as much “effective air” for a given rpm. Turbo and superchargers pressurize the input air and effectively increase displacement for a given rpm.

[@qasimmir7117]

Yes, flame speed exactly. He didn’t talk too much about that. The thermodynamic limit of the expanding gas.

[@c-ro311]

Please man, review your scripts better

[@alecmillea4539]

Just commenting to support the channel and video. Keep up the great work Scott. I really hope you keep getting good viewer numbers. I’m concerned you took a major hit from the algorithm after the overdrive debacle.

[@NLBassist]

A great vid! And it's not only about the final answer, but about all we learn in between.

[@PeterTurr]

Nice video. The problem that normally isn't one. The crystal clear comparison of translation and rotation would answer the question very quickly. Certain hybrid engines and their modifications would be very serious competitors, just like back then. You know what I mean and the history of the topic in racing with combustion engines. Peter

[@RJ-nh9hw]

Excellent presentation, educational of the first order! You bet I subscribed!

[@ben91069]

its the mass and strength of the reciprocating parts that define the acceleration and deceleration of the piston and connecting rod that limits the max rpm, just like a helicopter rotor and blade cannot exceed a certain speed because the rotary wing aircraft is already moving in air at a certain speed while the machine is also adding to that speed while the other hemisphere of the rotor is doing just the opposite so there is a point of imbalance so that a helicopter cannot go over 2-3 hundred knots. However, if the reciprocating mass is smaller, rpms can exceed 20k, it just depends on the balancing of the crankshaft and pistons so there are no harmonic imbalances.

[@kwaka140]

Standard Kawasaki ZXR250, 19,000rpm redline, but happy to rev higher. The speed of flame front is so slow an engine would not work above a reasonably low rpm. However, there's something called "squish velocity". In performance 2-strokes it's critical to get it just right. I suspect it's the same in 4-strokes. The velocity of the gas in the chamber is what reduces the burn time to allow high rpm and efficiency. It makes enough difference that ignition timing can be backed off at least 5°. I'd imagine modern materials and manufacturing techniques would allow for higher rpm if allowed.

[@ellipticalsoul]

It's mind boggling to me that they can even work at such high revs. Engineers who design and make these are insanely talented.

[@olafzijnbuis]

At 06:29 The length of the conrod has nothing to do with the stroke. The stroke is determined by the offset of the taps on the crankshaft only.

[@mrm7]

Thank you for fixing the voiceover sound. Both room treatment and the microphone

[@MrHaggyy]

Well, mechanical constraints do not limit you to 20k RPM, if going above that RPM is your only goal. What limits your RPM is time. It takes time to exchange gasses, build a flammable mixture, ignite the mixture, and then you want time for the mixture to push the cylinder down. A longer power stroke will extract more energy inside the engine and send less energy down the exhaust. So it's a design balance between energy sent to the turbo/MGU-H and energy kept inside the engine. Air exchange can happen close to the speed of sound, which is close to 350m/s at ambient and close to 700m/s at exhaust temperature. Reaction time is a view µsec. The speed of the flame of 0.5-3.5 m/sec is the limiting factor. So you don't want to rev higher because it would reduce the amount of energy you get at your crankshaft at a certain point, and you want to rev even lower to avoid heat and save on mass you would otherwise need for cooling. PreChamberIgnition (PCI) was also designed to save a lot of weight. With it, you only need a flammable mixture inside the prechamber. That flame can travel through mixtures that would be too rich or too lean to ignite. In an engine, the mixture is way too lean. So you get much more air to a slightly lower temperature and pressure. An engine that runs rich to stay cool at high rpm would burn 2-4x as much fuel. Which does not work with the current fuel limit and would still be irrelevant if you could use as much fuel as you would like. It would only be interesting if the cars would be significantly (200kg

[@rogerstone1318]

This is nonsense - 30 seconds on a calculatr will tell you that, in an ordinary car engine producing peak power at 6000RPM you have 5 ms for the entire power stroke if you maximum flame speed is 3.5 m/s then the flame will have progressed a whole 17.5mm in that period. What you are quoting is the flame speed through a quiescent, homogeneous mixture. What we have in an engine (even those with a "quiescent" chamber design) is a gas and fuel mixture which is anything but quiescent - we have very rapid gas movement which rips and tears at the flame front, streching it, pulling pockets of flame into the unburnt mixture and shoving misure through the flame - it's chaos! This effect speeds up combustion by orders of magnitude - and, the faster the engine runs the more energy is imparted to the gas so the energy that goes into "stirring that pot" increases with engine speed now at more conventional engine speeds and engine geometries (bore:stroke ratio) it is a happy accident that the effect of more energetic stirring almost perfectly matches the the reduced time available for combustion - so the combustion period, measured in crank degrees - which is what counts for these purposes, remains remarkably constant as engine speed changes. now I can imagine that, as over-squareness gets to extreme levels, like in a 20,000 RPM F1 engine, 2 things start to happen: the inlet gas velocity is atypically low because the mass of gas induced in comparison to the bore size is relatively low- big valves low mean inlet gas velocity - so the "stirring energy" will be lower and the flame speed could start to drop - hence the success of a pre-chamber. Similarly (and the video is talking rubbish here too) Stoichiometric is NOT where you want an F1 engine running - max power is at about 12.5:1 so there or a little richer is where you want to be - richer does give a petrol cooling effect but you can't go anywhere near "2-4x" as much without passing the flammability limit - which means the mixture would not fire. You also loose power as well as fuel consumption if you go richer. It is true that a pre-chamber can exploit the possibility of different A:F ratios in the chamber and in the main body and that is exactly what the Honda CVCC system did - nice and rich in the pre-chamber and lean, lean lean in the cylinder - to give overall a leaner mixture that you could reliably ignite with a sark and drop the NOx levels - that is not what is happening in an F1 engine. The speed of sound - ah, yes, it matters but not in the way implied and, honestly, life is too short. 45 years an engine design, development engineer - cars, bikes, F1, loco/marine, consumer industrial, you name it. I sympathise very much with @bythelee whose comments I thought excellent (Do I know you I wonder???? - it's a small world) and whose comments on current practice with respect to piston rings and their materials I would be fascinated to see - gas force vs TDC inertia force is a tricky area for very high speed applications. @MrHaggy, apologies if I have flamed you - there are many posts here that could have sparked (pun intended) my ire but you just happened to be " the one" - and it's a crappy video too - trying to make things clear for the layman does not excuse sloppy practices or spouting nonsense

[@tbone5654]

My remote control car with a nitro engine does 37,000 rpm. When I run it with the exhaust pipe off its like 10 times louder than a full sized car.

[@19Borneo67]

There is an upper limit, but I think it's controlled by gas dynamics, not by kinetics of the metal rotating parts. I'm pretty sure that they could make a machine that will rev faster than pressure disturbances can travel through a gas medium.

[@N.California]

20k is amazing, heck 9000 peak on an average car or truck defies belief. Into the realm of 10, 12, 15, and 18,000 RPM's is astonishing.

[@maleider5617]

Don't forget the Honda CBR 250rr MC22 from the 90s which could also rev up to 20000 rpm while it was street legal too. Other japanese bikes from that era were close to that too

[@fathertimegaming17]

I've seen this video on every car and engineering channel on KZbin already but welcome to the party.

[@crezychameau]

RC model engine regularly run around 30.000 rpm, and some even higher, i've seen up to 45k being suggested. Granted they run on nitromethane, which burns fast, but the mechanical aspect is still here. Just a little info to temper the "absolut limit" idea that seems to be played here

[@Eargesplitten-Loudenboomer]

I think the biggest limiting factor is not using v10's. You're not going to to come close in any other cylinder configuration for a passenger vehicle.

[@michaelhope007]

This is not true. The rental car I had 2 weeks ago revved well over 21000rpm. It also leapt tall buildings.

[@olafzijnbuis]

At 10:13 A complete 4-stroke cycle takes 2*60/20000 = 0.006 s You forgot that a full 4-stroke cycle takes 2 revolutions of the crankshaft. Still a very short time...

[@f800gt76]

he also didn't mention clearly a problem with lubrication. There is a limit of piston linear velocity about just 23m/s. Above that wearing occurs much much faster since oil film cannot restore so quick or so. Huge marine diesel and MotoGP prototype engine - both have the same limit, but marine diesel has stroke over 2 meters and revs a couple hundred times a minute, while MotoGP engine has stroke of just 50mm and revs 16k+ rpm

[@YodaWhat]

*AWWW* 2:57 "We are only focused on engines that have pistons." No turbines, sure, because they are not _positive displacement engines_ But Wankel engines are, and they can also rev quite high. When Mazda factory representatives happened to come to my school in the early 1970s, they said the factory had taken a regular Mazda Wankel as used in the RX7 car, removed the rev limiter and added a supercharger, and that little engine could run 25 THOUSAND RPM. Further, they said the mechanical 'blowup speed' of the engine was _a whopping 78,000 RPM!_ There have been successful racers of Wankel engines, and compared to the extensive work needed to rebuild most race engines, Wankels can be rebuilt quite quickly, at relatively low cost. Wankels can 'breathe' far better than piston engines because they can use the large area on the rotor sides as intake port area, like a 2-stroke engine, yet Wankels are 4-stroke engines. Yes, they have poor fuel economy, but c'mon, we are talking about RACING ENGINES.

[@geemy9675]

peak cylinder pressure in a race engine 1500psi. probably even more win a race engine, so with 80mm bore that's over 15000kgf pushing on the piston

[@Georgianson]

You talked about increasing RPM and therefore increasing power leading to faster laps. So it's logical to conlude that power makes the car faster... I believe it's something that needs to be explained in videos more often to people.

[@jamesfairmind2247]

Are most F1 pistons 2 ring or 3 ring, or both types?

[@CmdrTobs]

The strict theoretical limit is friction. At some RPM frictional losses in the moving assembly, *but more fundamentally in intake and exhaust gasses* become the limit aka 'pumping losses' and pumping losess increase faster than power gain as RPM increases. Friction *cannot be zero* for gases as gasses can't be Bose condensates. So theoretical RPM limit is when Power = Friction Power. Flame front v, material strength etc.. are all practical engineering limits, but only engineering limits...

[@ZsebtelepHUN]

Probably the best video so far on the channel, loved it

[@danielc4361]

Very effective explanation about engines in general especially 2 vs 4 stroke

[@jools77]

Except he was explaining a petrol (gas) 2-stroke, and showed a schematic of a diesel 2-stroke 🤦🏻😂

[@StelaPop]

fantastic video thank you for making it🎉

[@MotoroToada]

There's no rpm advantage for a 2-stroke other than not having a valvetrain. 500cc 2-stroke GP bikes revved to 12k rpm while the first gen 990cc 4-strokes that replaced them revved to 14k rpm, and they're at 18k rpm now.

[@bogeycrow1968]

You stated with 2 strokers combine intake and exhaust in a single stroke and compression and power in a single stroke. It’s actually exhaust/compression then power/intake.

[@jasonk4569]

My stock 1999 Honda CBR250RR with 55,000km on the odometer routinely hits 21,000rpm and they are known to hit 23,000rpm without issue. Redline starts at 19,000rpm

[@ChrisNett42]

I used to have a nitro RC car with a tiny aluminum single cylinder engine that did 29,000 RPM. That thing was awesome!!! HPI has a 3.0cc 2 stroke engine that will max out at 32,000 RPM!!!

[@matthiasweidmann8135]

........except Ferrari had F1 engines running at 24.000 rpm ....and could have raced them. Paolo Martinelli was in charge at that time from 2002 - 2012 and was only limited by supply of pistons. Mahle delivered the best material....but quantities were limited. So at races with high full throttle mapping the full power was executed. At the rest of the races standard engines up to 21.000 revs were employed. The glorious years of "rev festivals" are over for the moment. But are coming back as " electric turbines" , brushless inrunner with easily 30.000 revs maybe soon...but of course mainly silent as efficiency is king!

[@objednavkystesticko]

It would be interesting if that TGI ignition could be applied to old cars. What effect it would has on performance and efficiency.

[@Pegaroo_]

0:11 Nope it's mass is exactly the same as it was when it's stationary. The forces acting on it may well be the equivalent of 2.5 tonnes but it's mass does not change

[@michaelcarydakis790]

what if you ceramic coat the pistons and block and use rotary valves in the head this is more air to

[@simonebertulli1232]

Raikkonen in 2006 quali in Imola reach 22k ...there's an onboard video

[@clivenorton2834]

Wrong. My 1992 Kawasaki ZXR250 revved to 21K. Admittedly the redline was 19k, but that was just a bit of ink on a dial face. The engine went to 21K. On a road vehicle. That survived at least 20 years - I sold it early 2012 with no known issues. 4 stroke. 4 cyl. 16 valves. 4 carbs.

[@jools77]

The 2-stroke diesel which appears at 5.15 is fundamentally different to a 2-stroke petrol engine. Moreover, in the context of efficiency they are opposite ends of the scale: 2-stroke diesels are THE most efficient internal combustion engines ever built. @Driver61 you may also wish to licence the Phil M Karting clip at 4.42 instead of treating it as a free resource

[@1arritechno]

Small Glow Plug engines can run 40,000 RPM.. Minimize reciprocating weight & stroke - exceeding 21,000 is doable...

[@rcabert70]

Great video, but what happened to the Cosworth piston design video?

[@yazgaroth]

Very interesting! Thanks!

[@willohm5439]

At work, I'm designing something to spin at 15-20kRPM with an oil bath and it's got tons of issues - and it's not even reciprocating! I can't imagine designing an engine to go that fast

[@mcsniper77]

Two stroke engines are much more complex in theory as there are several things happening at the same time. Two strokes actually left rev lower. If you want to make the same power with a four stroke is a 2 stroke you have to spin it twice as fast.

[@ryanakahoward5246]

I'm a minute in and I'm gna guess the sponsor today is brilliant. Edit at 3 mins in....nailed it.

[@Terrorist939]

Now this makes me think, if we used a rotating valve instead of regular ones. Some people have tried it, with varying success, but it has never been done by big companies that have the funds and equipment to make something ridiculous.

[@cjgordon22]

I once heard the reason they can't go over 20k is because the air moving into the cylinder was going to travel faster then the speed of sound and that would make it unstable. But that could be way off

[@John-jl9de]

We want 20,000 RPM engines back in F1. They sound powerful and made for some great racing. Who cares if the hybrid cars are slightly quicker, it's a show and we want the music to go with it. These modern cars sound like shit.

[@IgnitionP]

6:26 Note that the length of the connecting rod doesn't affect the cylinder stroke at all, it is the crankshaft that affects it

[@MrAdopado]

True. The crankshaft affects the minimum con rod length but not the maximum so in theory it could be longer and still have the same stroke ... but I can't think why anyone would choose a longer con rod than absolutely necessary, so in that sense the crank defines the con rod length and to that extent it boils down to the same thing.

[@IgnitionP]

@@MrAdopado you should watch the video by d4a about rod ratios. A longer con rod is actually better