About RPM

[Fe662]

There's vantage of a 10,000rpm car in a 7,500rpm car or nothing changes?

 

[PawnBoy]

There's vantage of a 10,000rpm car in a 7,500rpm car or nothing changes?

No, I don't think there's any advantage to putting a 10,000rpm car in a 7,500rpm car. Even if you could fit the one inside the other, the 10,000rpm car wouldn't be able to put any power down to the ground (since it's inside the 7,500rpm car), and would just add lots of weight to the 7,500rpm car. The handling could also be hugely disrupted. Besides the slim odds of getting the two cars balanced fore and aft, the center of gravity would be raised by a couple feet, resulting in enormous body roll (and I don't think setting each of the springs to the highest setting will help).

So all in all, I'd recommend against it.

 

[Gran_Turismo]

I'm lost just by reading both responses.

Are you asking if there are performance differences in changing the RPMs in a car or are you trying to compare?

 

[Jaywalker]

No, I don't think there's any advantage to putting a 10,000rpm car in a 7,500rpm car. Even if you could fit the one inside the other, the 7,500rpm car wouldn't be able to put any power down to the ground (since it's inside the 10,000rpm car), and would just add lots of weight to the 10,000rpm car. The handling could also be hugely disrupted. Besides the slim odds of getting the two cars balanced fore and aft, the center of gravity would be raised by a couple feet, resulting in enormous body roll (and I don't think setting each of the springs to the highest setting will help).

So all in all, I'd recommend against it.

ROTFLMFAO!!!!!! Bwaaaaahahahahah!

 

[VBR]

There's vantage of a 10,000rpm car in a 7,500rpm car or nothing changes?

 

[adeadsnipermatt]

no, i don't think there's any advantage to putting a 10,000rpm car in a 7,500rpm car. Even if you could fit the one inside the other, the 7,500rpm car wouldn't be able to put any power down to the ground (since it's inside the 10,000rpm car), and would just add lots of weight to the 10,000rpm car. The handling could also be hugely disrupted. Besides the slim odds of getting the two cars balanced fore and aft, the center of gravity would be raised by a couple feet, resulting in enormous body roll (and i don't think setting each of the springs to the highest setting will help).

So all in all, i'd recommend against it.

Oh god died!!!

 

[Jaywalker]

Oh god died!!!

Funniest I've read in ages!

 

[DnBasshead007]

No, I don't think there's any advantage to putting a 10,000rpm car in a 7,500rpm car. Even if you could fit the one inside the other, the 7,500rpm car wouldn't be able to put any power down to the ground (since it's inside the 10,000rpm car), and would just add lots of weight to the 10,000rpm car. The handling could also be hugely disrupted. Besides the slim odds of getting the two cars balanced fore and aft, the center of gravity would be raised by a couple feet, resulting in enormous body roll (and I don't think setting each of the springs to the highest setting will help).

So all in all, I'd recommend against it.

whatttttttttttttttt? HILARIOUS!! 👍

 

[HJLamont]

i had some idiot online giving a "lesson" in car mechanics. he was telling this kid that what you want in a car is the highest RPMs possible, that its all that really matters in racing a car, you can have 200hp and 12,ooo rpm and beat a car with 700hp and 6,ooo rpm. any argument was met with some blathering nonsense.

idiots. i hate idiots.

 

[PawnBoy]

i had some idiot online giving a "lesson" in car mechanics. he was telling this kid that what you want in a car is the highest RPMs possible, that its all that really matters in racing a car, you can have 200hp and 12,ooo rpm and beat a car with 700hp and 6,ooo rpm. any argument was met with some blathering nonsense.

idiots. i hate idiots.

Well, if that's what the question is about, if the maximum power is the same, the lower rpm'd car is probably better in my mind. Correct me if I'm wrong here, but a low rpm motor is more likely to have a wider torque and thus power band since it's easier to tune an engine for a small rpm range. So the low rpm engine would be more useful than an engine with the same maximum power, but only at a high rpm peak.

 

[Eunos_Cosmo]

Well, if that's what the question is about, if the maximum power is the same, the lower rpm'd car is probably better in my mind. Correct me if I'm wrong here, but a low rpm motor is more likely to have a wider torque and thus power band since it's easier to tune an engine for a small rpm range. So the low rpm engine would be more useful than an engine with the same maximum power, but only at a high rpm peak.

I'll just say, not necessarily.

A car that only revs to 2,000rpm would not be a good racing car. There is little flexibility with low RPM engines. Not to mention the fact that horsepower is DIRECTLY PROPORTIONAL to RPM. In general, the more RPM you can get, the more power you make, provided you can still make torque at high RPM.

In a perfect situation, if you had 2 engines that both made 200lbs*ft of torque from idle to redline (totally unlikely) and one revved to 5,000rpm and the other to 10,000rpm, the higher revving engine would be much more powerful. Twice as powerful actually.

 

[PawnBoy]

I'll just say, not necessarily.

A car that only revs to 2,000rpm would not be a good racing car. There is little flexibility with low RPM engines. Not to mention the fact that horsepower is DIRECTLY PROPORTIONAL to RPM. In general, the more RPM you can get, the more power you make, provided you can still make torque at high RPM.

In a perfect situation, if you had 2 engines that both made 200lbs*ft of torque from idle to redline (totally unlikely) and one revved to 5,000rpm and the other to 10,000rpm, the higher revving engine would be much more powerful. Twice as powerful actually.

Well yes, but I was holding power constant between the two engines in my example, not torque. You're correct, for a lower rpm motor of the same power, the torque figures have to be higher. If you have 2 engines, each making a maximum of 200bhp, and one revved to 5,000rpm and the other to 10,000rpm, odds are that the 5,000rpm motor would have more useable power.

 

[Vince_Fiero]

Whow the discussion did get a bit better after the first reactions.

RPM is indeed not the full story:

It states how fast your engine turns, nothing more.

Depending on the output of torque, you can use other gears, which make it work better or worse.
Depending on the power you can generally develop higher speeds.
So the discussion on Torque and Power together with gearing is the most important, the RPM is just a property of the engine that adds little to the discussion.

Clearly you might have to change gears less if you can use a high torque zone between distant RPMs, but again more a property of the curves then the RPMs.
The high torque slow running agricultural or marine engines could be used to show that very low RPMs are not useful for cars, but there this discussion stops for me.

 

[PawnBoy]

Clearly you might have to change gears less if you can use a high torque zone between distant RPMs, but again more a property of the curves then the RPMs.
The high torque slow running agricultural or marine engines could be used to show that very low RPMs are not useful for cars, but there this discussion stops for me.

Too true. My car makes close to 175hp, but only up around 6,000rpm. It probably only makes about 80hp at 3,000rpm, and at an 1,500 is probably capable of around 20hp. The car is tuned to make torque above 3,000 rpm, so this is where you have to be to make power, and after 5000 rpm the torque starts to drop again, and drops ever more sharply as rpms climb.

Where as one of the tractors on my father's farm makes 200hp at around 2,000rpm, and idles at 1,000rpm, where it's still probably capable of close to 100hp. Not that hp matters much to tractors, but since the engine rpms only fluctuate by a maximum of 1400rpm the tractor's was able to be tuned to have a very flat torque curve(more like a line), so power is super predictable and there is no fluctuation in torque based on rpm.

Of course, the disadvantage of low rpms are that the engines are typically bigger and heavier. The car has a 2.5L boxer 4, and the tractor has a 6L inline 6....

 

[Mr. CoolFiat]

Whow the discussion did get a bit better after the first reactions.

RPM is indeed not the full story:

It states how fast your engine turns, nothing more.

Depending on the output of torque, you can use other gears, which make it work better or worse.
Depending on the power you can generally develop higher speeds.
So the discussion on Torque and Power together with gearing is the most important, the RPM is just a property of the engine that adds little to the discussion.

Clearly you might have to change gears less if you can use a high torque zone between distant RPMs, but again more a property of the curves then the RPMs.
The high torque slow running agricultural or marine engines could be used to show that very low RPMs are not useful for cars, but there this discussion stops for me.

The discussion is just like a powerband, it starts out slow and gets better exponentially, then there is some dude who just blows it at the end and the discussion ends up locked.

 

[Jaywalker]

Personally, I preferred the beginning...

 

[Duck]

You need more rpm to have more power. If you take an engine revving 7500rpm and tune it to 10000rpm you simply gain power, so is better.

You can't compare revs between two different engines, unless they share architecture (nr. of cylinders and disposition: inline, flat, V, etc). So a 7 liters V8 'probably' have less rpm than a 2 liters inline 4, and rpm say nothing about which is the most powerful.

 

[Sm0k3:D]

Well, if that's what the question is about, if the maximum power is the same, the lower rpm'd car is probably better in my mind. Correct me if I'm wrong here, but a low rpm motor is more likely to have a wider torque and thus power band since it's easier to tune an engine for a small rpm range. So the low rpm engine would be more useful than an engine with the same maximum power, but only at a high rpm peak.

OMG! You like diesel engines! Don't tell this too loud! XDDDD

 

[witham]

Well, if that's what the question is about, if the maximum power is the same, the lower rpm'd car is probably better in my mind. Correct me if I'm wrong here, but a low rpm motor is more likely to have a wider torque and thus power band since it's easier to tune an engine for a small rpm range. So the low rpm engine would be more useful than an engine with the same maximum power, but only at a high rpm peak.

Only problem is gear management becomes a problem, the is no definitive answer to this poorly worded question.

 

[mvpers]

OMG! You like diesel engines! Don't tell this too loud! XDDDD

yes, i do too, especially the Audi R10 TDI

 

[ToreDL87]

I seriously doubt you`d be able to gain anything past 9500-10000rpm (And thats pushing it HARD), because most tuners dont know jack **** about high rpm engines, and even if the tuner knows what he`s doing, the tremendous friction the engine internals will be going through for EVERY stroke (RPM) past what it`s factually capable of, will result in lost torque even if the HP numbers go up and up. Then theres the cost of building a 11000 rpm engine, and the cost of maintaining it..

It`s better to get the engine tuned to max 8500-9000 rpm and rather tinker with the gear ratios and suspension, you`ll get a engine that you can abuse all day long and power thats easier to manage, 9000 rpm is more than high enough

In WRC they mostly limit the RPM at 5500 @ 300HP, they can pretty much go straight from 2nd gear to 4th when exiting a hairpin going 90 degrees sideways and onto a long winding stretch, and still beat the time trials with a huge margin.

Even on race track events it`s noticeable.. Just look at those fancy sponsored machines that always have mechanical trouble because they go so overkill on the engines that when they do have trouble they have to retire from the race because the expert that built the engine isnt available, whereas the privateer guys who spend their money on having the engine tuned for durability and power are rewarded with being able to race the track all day long and hone their skills.

 

[PawnBoy]

Well, it's not unheard of for production engines to have astronomical rpms. Take the 1986-1999 Honda CBR250(R(R)). Powered by the little 4-stroke 250cc inline 4 MC14e engine which has a redline of up to 19,000(!!!) rpm on some of the models. Being a 250cc engine you'd expect it to put out a little less than 30hp, but with the absurdly high rpm and incredible engine design, the MC14e put out 45hp! 50% more power than most similarly displaced engines (though I think all 4 japanese manufacturers made high rpm 250s at one point). And the MC14e engines don't have a history of breaking either, purported to easily last 100,000km (a large distance for any motorcycle) without any serious maintenance.

If I ever have room in my garage and budget for a toying around bike, I want one of these.

 

[sumbrownkid]

Higher rpms in cars means less reliability more often than not.

In the real world, low end torque is more useful than high end power.

Which is why I don't understand when vtec fanatics get worked up whenever I say your Honda has the torque capacity of a bicycle.

 

[PawnBoy]

Higher rpms in cars means less reliability more often than not.

In the real world, low end torque is more useful than high end power.

Which is why I don't understand when vtec fanatics get worked up whenever I say your Honda has the torque capacity of a bicycle.

Well actually, consider that a bicycle's crank turns at around a nominal 60-90 rpm, if it's making 1hp (say the rider is hill climbing, and not exhausting), at 60rpm that crank is putting out 87.5lbft of torque! Also consider that a bicycle can put down even more torque at lower rpms, even higher when stalled. Torque is really the only thing a bicycle has, and it's more power that it needs.

 

[sumbrownkid]

^That's interesting math right there.

My cousin (huge vtec fanatic) gets ticked whenever I say your Civic screams, but doesn't move much.

 

[Famine]

Higher rpms in cars means less reliability more often than not.

Err, cobblers. Most reliable engines in the world? Honda VTECs... No unit failures outside of the service schedule attributable to a fault since their introduction.

In the real world, low end torque is more useful than high end power.

Double cobblers.

A car that doesn't generate any power can't be prompted to make any more - you're stuck with what it makes. A car that doesn't generate any torque can be prompted to make more, by the simple act of changing gear - gearboxes multiply torque and a lower gear has a higher ratio and a higher mutiplier. Quick, dirty example - in 4th gear I have a torque peak of about 750lbft, in 3rd gear it's 980lbft, in 2nd gear it's 1,700lbft.

The only time a high amount of torque matters (and cannot be compensated for by changing down a gear) is in moving significant loads - either a high mass payload or a normal load up a steep incline.

If you're not towing or hill climbing in first gear, torque is irrelevant to "real world" driving so long as you can find your gearstick. And in fact crank torque is irrelevant to anything as it doesn't move you anywhere.


Oh, and power is a measure of torque converted to useful work. 200hp is 110,000lbft per second, regardless of whether the car producing it has 400lbft or 140lbft at the crank.

 

[Bobalob]

torque is the only thing that matters... all other engine power calculations are based on it.

 

[PawnBoy]

torque is the only thing that matters... all other engine power calculations are based on it.

As Famine just mentioned above, torque is necessary, but certainly not all that matters.

 

[Famine]

More than that - crank torque is the most useless measurement of an engine because it tells you nothing about the car's abilities. Wheel torque is what moves you places and wheel torque is subject to the multiplication factor of the gearbox (power is not). All the torque in the world at the crank won't move you through a 1:200 gearbox (most gearboxes are 2.5:1 for first gear and 4:1 or so for the final/differential gear, so about 10:1).

 

[Tispower]

Err, cobblers. Most reliable engines in the world? Honda VTECs... No unit failures outside of the service schedule attributable to a fault since their introduction.



Double cobblers.

A car that doesn't generate any power can't be prompted to make any more - you're stuck with what it makes. A car that doesn't generate any torque can be prompted to make more, by the simple act of changing gear - gearboxes multiply torque and a lower gear has a higher ratio and a higher mutiplier. Quick, dirty example - in 4th gear I have a torque peak of about 750lbft, in 3rd gear it's 980lbft, in 2nd gear it's 1,700lbft.

The only time a high amount of torque matters (and cannot be compensated for by changing down a gear) is in moving significant loads - either a high mass payload or a normal load up a steep incline.

If you're not towing or hill climbing in first gear, torque is irrelevant to "real world" driving so long as you can find your gearstick. And in fact crank torque is irrelevant to anything as it doesn't move you anywhere.


Oh, and power is a measure of torque converted to useful work. 200hp is 110,000lbft per second, regardless of whether the car producing it has 400lbft or 140lbft at the crank.

Relatively high torque would however enable you to stay in a higher gear and lower the engine rpm and thereby save fuel. As IC Engines are most efficient @ low rpm, high load states. In GT5 however, you don't really need to do this.