So you have a hot rod. Ever wonder if it would be faster with more RPM? The answer's simple - once you think it through logically. If this was helpful to you, consider donating a buck or two to my Patreon: / alexltdlx
Thank you for explaining this so clearly. Lots of people seem to think that a motor with lots of torque can beat a motor with higher horsepower, and completely fail to understand that torque is worthless without RPMs. You can make a 15000rpm motorcycle engine pull a tank by changing your gearing.
Well put. 500hp is 500hp. All that matters is effectively getting it to the ground. 500hp at 12000 rpm is useless if you can't get it through a transmission.
I thought this was a comparison on 5000 rpm vs. 7000 rpm with the same hp? All of a sudden, there is a lighter rotating assembly in the 7000 rpm motor 🤦🏻♂️
an engine that spins a higher RPM but makes the same power is going to have a lighter assembly physically you almost cant get around that now the 500 HP @5000 RPM is doing it with nitrous vs 500 @7000RPM N/A and now ive thrown in a can of worms 400 HP 347+100 shot vs 500HP N/A 302
@KingJT80 has nothing to do with needing. It all has to do with a very straight-up comparison. Once you change one engines rotating assembly weight, it's no longer a fair comparison. That is all I was saying.
My initial guess was that they would be the same, provided yes gearing equalized torque to the ground, since horsepower is just torque per time essentially. I also thought the 7,000 RPM car might have an advantage due to some kind of efficiency, but I couldn't really think of why. Thanks for the fun video.
You can do some fun math with this… if 5000rpm and 7000rpm are happening at the same wheel speed, wheel torque is identical 🤣 both cars will accelerate identically as long as they average the same power… with a CVT (just because it’s easier to explain) the RPM is constant and the gear ratio is irrelevant, as long as the HP output is the same with different engines the wheel torque will remain CONSTANT even know 2 engines might output WILDLY different torque… it’s all math, horsepower how much work the torque is able to complete. And torque is how hard it’s twisting
Yes, that is what i am saying every time. It's wheel torque that count not crank. But some of them dumbasses don't really understand what "at the wheels" mean. They see a power and torque number saying at the wheels and this is where their information processing stops.
@@PistonAvatarGuy It gets more challenging to figure out when you consider only a single shift too in this drag racing situation. More flywheel might actually help and you might get to recycle the energy on the 1-2 shift
From a physics standpoint, both of them would finish simultaneously. This is easily derived from the energy conservation law, since all the speed comes from kinetic energy and all the energy comes from power, which is incidentally a measure of energy over time. The RPM or torque itself play no part in a calculation. Of course, it should be mentioned, the cars here are "ideal" in a sense that they experience no losses and apply full power throughout the race.
If we are dealing with reality, the motor with more area under the curve(in relation to power and rpm) will produce more average torque over its power band. Also, drivetrain parasitic action has to be taken into account. The car with the least dynamic drivetrain drag will be easier to propel. Aerodynamic drag is also a big factor in the ultimate top speed of the car.
The one with the lighter engine and transmission rotating parts would win. If they're the same, then the cars should be even; but with manuals, you lose a lot of time shifting - no matter how good you are.
That was definetely the Einstein answer - impressive. Put another way, the higher RPM engine can take more advantage of "gearing".. Imagine a 700 HP @1000 rpm. Yes? No? Let me have it :O) Cheers.
Usually it is because if you just spin the motor faster the AFR in the cylinder get's worse and worse because the mix is to slow through the drag it gets from intake, air filter and so on and thorugh that you loose more power than you gain. But if you tune it with a bigger intake and exaust and everything then it still can "breath" at high rpm and produce the same torque at higher rpm.
I can see why you'd see it that way. But if I just put up a video like this and went on camera and said, "it depends," I'd get crucified. 99.9% of the time, the higher rpm car will win. It's a very specific set of circumstances that are somewhat unlikely where it wouldn't. The intent of the video (which perhaps I could've mentioned) is more as a guide of how to build a quicker car - go for more rpm (unless, of course, there are other constraints). But as another commenter pointed out (and I made a point of saying), these are hypothetical cars. This video came about because I'm thinking of adding about 500 rpm to my own car, specifically for the converter reasons I'd mentioned. I'm currently seeing about 11-12% slip at the stripe - I'd like to see about half of that ideally.
@@AlexLTDLX If youre talking real world actual improvements there is no general rule. It usually comes down to what is most cost effective vs. performance gains. What if you have valve float and a "dying" power curve already? Then you need to fix that before upping the RPM. Someone else might anyway need a bottom end rebuild, maybe it makes more sense to go for a 383 build over a 350 in that case. Though for a future video I would like to know more about converter tuning as I have no experience of that and would ideally want to build myself a nice street/strip Powerglide car (the one in mind would be really light) and it would be interesting to understand where the sweetspot would be for a 1/8 mile strip and street car.
Those are all valid points; which again is why this is a hypothetical. For a glide, you want anywhere from around 700-1,200 rpm fallback on the shift, with enough stall and torque multiplication (also known as "k factor") to get it out of the hole as hard as possible without tire spin. In an optimized 1/8 mile car, you'd want to see less than about 14% slip - in a quarter mile car, you'd want to see less than 10% - ideally around 6% or so. If you have a really high winding engine, it's possible to be in the mid single digits for slip in the eighth. I'd do a video on converter tuning, but I don't think it'll get a whole lot of views based on the demographics of my audience here, unfortunately. Keep in mind that raising the shift point generally doesn't change the rpm that the engine will fall back to on the shift (assuming you haven't added power). Hope this helps. BTW - I did do one converter video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-icVw-QA3QLo.html
All things equal as stated in the beginning of the video they should be parallell all the way. Of course in reality you need to talk area under the curve and other details which does not make it that easy. Still, horsepowers wins races, unless the way of utilizing that engine is less efficient than utilizing a different less powerful one.
@@bingoberra18 I agree. But to add nuance and make the conversation more complete, acceleration closer to the starting line is more important than the same acceleration later. Acceleration is from force/mass. Force is torque. Put more torque to the pavement earlier and the car with more torque but the same power gets a head start and can beat a car with more power. I.e, look at ev's and how good their ETs are vs their trap speeds, and 4 cyl turbo cars which are the opposite. This is why I'd like to see /do a side by side comparison. Imagine something like a 3rd gen Camaro TPI 400 vs one with a Victor jr on a 302. Tune both to make 300 wheel and otherwise identical except for the rear gear. Given the torque curve for each motor, it would be simple to make a graph of a 1/4 mile on the x axis and put acceleration on the y axis.
@@mxguy2438 Sure, but in the example the lower torque engine was geared to equal the torque to the ground of the higher torque engine, this can be done also in real life. However at the launch having a lot of rotating mass might be of benefit since it might help setting big slicks in motion. I just dont really like this video as it goes out saying they are equal in every way, and then starts changing that. If they are truly equal besides rpm and geared for the rpm then there is no actual theoretical difference in the acceleration or torque to the ground. Where the example falls is that in reality there are so many variables and there is no point in discussing it theoretically. Better to just analyse what is actually winning on drag strips around the world and why theyre winning.
@@bingoberra18 and what USUALLY wins around the world? high RPM engines that get into the power band quickly and make power up higher. not a lot of low grunt engines wins races...unless the entire class/rules are built around specific parameters for that to happen
In the late '70s I had a '70 Cuda with a mild 440 auto and 4.11 gears. I tried a set of 4.56 gears and ran the same ET. The only difference was RPMs through the lights. Can you explain?
Without more data, I'd have to give it my best guess. The converter was effectively tighter with the 4.56 gear ratio because it was loaded less - but this would be a slight difference because going from 4.10s to 4.56 isn't that big of a difference in a mild combination. Weather is the more likely culprit - it wouldn't take much to lose a couple mph. When I used to run the Whipple on my car, the difference between so-so air and great air was as much as 6 mph - 131.xx vs 137.xx.
My favorite is 500+ hp @ 8000 rpm, flat-plane crank DOHC V8, dual-clutch Tiptronic transmission, 2 seats, and a curb weight of 3500 lbs or lighter. Ferrari FTW.
Fox is always the answer though. In this case, a Fox with a Voodoo and BMW DCT. Suddenly we've hit every one of your targets for like... 50-60k making someone else do the dirty work.
IMHO, not enough variables defined in the opening statement. If only the engines and gearing are different, I'd bet the parasitic losses in the 7000 rpm setup, would be higher and the 5000 rpm combo would win. Windage and sheering the oil losses would be enough to give the win to the 5000 rpm combo. But optomizing each combo and being on a track would be a good race. Interesting bench racing subject.
@@AlexLTDLX well then I'm even more lost. Are we talking about real engines or hypothetical engines? And how is the comparison fair if one engine makes more power if you rev it higher? The way I understand it is that we have two engines who produce peak power at different rpm. However, since the power is identical, their top speed will be identical (assuming everything else is equal). So the question becomes which one accelerates faster. And I think the 5000rpm accelerates faster because it has to have more torque to reach that hp at lower rpm than the other engine.
and btw, I have 0 on-hand experience with powerful engines and sprots cars. I'm just trying to understand how that stuff works based on my previous knowledge. I might be totally off
Torque at the flywheel is irrelevant. In fact, a common point of confusion is that torque by itself does no work - it isn't power. I go into detail on this in this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fT_l27c-bZg.html Keep in mind nobody races at idle; or low rpm for that matter. Converters are specifically designed to flash into the engine's powerband - and the more a converter flashes (i.e. higher rpm), the easier it is to make one with a higher K factor (torque multiplication) that also still comes closer to locking up at higher rpm (as mentioned in the video - the further up the rpm band you go, the less slip you have - the 5,000 rpm engine is likely to see as much as 20% slip at peak power; I'd expect the 7,000 rpm engine to be around 5-6% - a huge difference). You are correct about the top speeds being equal.
@@AlexLTDLX I understand the difference between torque and power, but saying that torque does no work is like saying "guns don't kill, it's the bullet that kills". Power is torque x rpm, so if the torque of the 5000 rpm car is always higher than the 7000 rpm car in the 0-5000 range, then it will have more power across the range. Now that I'm thinking about it, it's not fair to compare power of both cars at the same rpm since the 7000 car can go higher so it will have a different gear ratio. About the torque converter, that flew completely over my head. I understand what you're saying, but have no idea if that's actually how they operate. I'll concede that you might be right for automatic transmissions (which now also makes sense why you were talking about transmissions in the video), but what if the cars are single speed manual? Would the 5000rpm car reach top speed before the 7000rpm car? (with gear ratios that make them reach the same top speed)
Bs... it's not the tq at a given rpm. It's overall power and tq through the entire rpm that matters a ton also... example. All things are equal both are 350 hp same gears same converter and theoretical same traction. One makes 350 on nitrous the other is all motor.. both end up makin the same power.... the nitrous car will smoke the other... it makes far more overall power than the other... period and no way around it
Power takes torque into account - your second sentence is redundant. If the nitrous car and the N/A are both geared appropriately and have converters that match the engine's power bands, and both make the same peak power, the results will be as stated in the video. Also, the nitrous car's converter will either be super tight N/A or super loose on spray (like 20% + slip at the big end) - don't get me wrong, the nitrous car would be more fun to drive (until the bottle runs out), but the physics don't lie.
Richard is a good guy, but he races dynos, not cars. In this case, we're talking mostly driveline and acceleration effects which isn't Richard's forte. Again, his info is valuable, but it's not a complete picture.
@AlexLTDLX I 100% agree. Torque is great except when you can't keep your tires planted. I have a 23 silverado with the 10 speed and I can spin the tires without launching it from a stop because of the gearing in 1st. Spinning tires doesn't get you anywhere, power is only useful if you can put it down, so making power at higher rpm gives the same advantage as boost by gear in a way.
But if both cars are exactly the same exept the time they produce top power and you would make a pull from low rpms wouldn't the 5k car be faster because it delivers the 500 hp erlier. Well 500 is a lot but if you would like take 100 so the weels don't spinn and you don't do a standing start like say in 2nd gear at 1500rpm?
Yes, but it depends. If it's a manual transmission car, then no, there won't be much difference. An automatic will absolutely be faster for the reasons I explained in the video.
@@AlexLTDLXIrreverent statement to the question at hand. In 2 identical cars the one that makes the 500 at a lower RPM wins. Unlike the video where you dance around different gearing and tq converters
Ok, if you insist. But in the vast majority of cases, you're wrong for all the reasons I've explained. On the other hand, just for grins, give me one reason why the 5,000 rpm car would win. I've spent 30 years making custom positive displacement power adder setups. I know torque. And I know it's fun on the street & great for breaking stuff but useless for winning races.
@@AlexLTDLX Again; if both cars are identical, with the same gearing, the one that males 500@5k will always make more tq and therefore more usable power under the curve, without the need for a gearing Handicap
No, the 5,000 rpm car won't make more torque at the wheels (the only place it matters). It'll make the same torque at the wheels. Watch the video - it's explained with visual aids. Torque isn't power. In fact, torque does no work by itself. I go into detail with this here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fT_l27c-bZg.html
