About RPM

[PawnBoy]

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.

Again, it's not "high torque" per say, it's a broad torque band instead of a peaky band. If the torque is spread across a larger rpm range, then it follows that more power is generated at lower rpms, but less at higher rpms. This is what is described as a "torquey" engine, and has more "useable power" because the engine does not need to be run in such a specific rpm range to develop significant power, but won't generate as much top end power as a more highly tuned engine. This more convenient for novices, and everyday road cars, but imperfect for high performance, as a keen racing driver will be able to keep the engine operating in a narrow rpm range, so that it may be tuned to deliver as much power from the engine regulations as possible.

 

[Exorcet]

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

If we're talking about going fast,

acceleration = Force/mass

Force = power*velocity power/velocity

Power is not multiplied by gearing like torque is, so from your RPM, you basically know your power, which tells you the force, which gives you the acceleration.

 

[dening80]

Is it too basic to say that higher RPM is required to get more power from a given displacement? That's how I see it, Naturally aspirated low capacity engines require high rpm to attain more power from their small displacement.

In relation to the direct question, it like most things is useful only if you can use it, as has been mentioned there are gearing issues which effect use of available torque and power.

Finally on the question.
I know it was poor and that there are standards we agree to on here... but given that this is an international forum open to all ages and backgrounds I think we should try and be constructive at heart first. Maybe correct the question first, that way someone has at least had the opportunity to learn something before being humiliated. You can usually tell whether what someone has written is lacking due to laziness or simply lack of awareness. Well that is the stand I think will take.

 

[Zenmervolt]

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.

The practical concern is not how much power the engine makes, but how much torque is available at the wheels and that's heavily dependent on gearing.

If one engine redlines at 6,000 RPM and another redlines at 12,000 RPM, the second engine can take advantage of much lower gearing and unless there's a significant power differential, the second engine will be better for racing.

http://www.vettenet.org/torquehp.html

It's better to make power at high RPM and take advantage of gearing in a racing scenario.

Now, outside of a racing track, it's generally more pleasant to drive a car with a broader powerband. While gearing can definitely compensate for a lower-torque engine, there's a practical limit to how much people want to shift and most people also don't want to be turning 5,000 RPM in top gear at 60 mph. For the style of driving that most people do on the streets, a car with lots of low-end torque and a lower redline will feel more "relaxed" and will therefore be preferred. On a track, however, things are different.

 

[Exorcet]

The practical concern is not how much power the engine makes, but how much torque is available at the wheels and that's heavily dependent on gearing.

But that's why there is power. It takes gearing back out of the equation.

I looked at your link and though the guy was right, he was confusing and I didn't like his example.

I like this guy's article

http://www.allpar.com/eek/hp-vs-torque.html

If one engine redlines at 6,000 RPM and another redlines at 12,000 RPM, the second engine can take advantage of much lower gearing and unless there's a significant power differential, the second engine will be better for racing.

Yes, an engine gains performance from more RPM [because it makes more hp, not because of gearing]. But that's only for a given engine. Get two different engines and the RPM doesn't tell you anything.

Also, about that guy's super Vette example, you would have to be crazy (or Chaparral) to leave that car with only 1 gear. The "supervette" peaks around 900 hp according to him, but only at redline. This means it would only see 900 hp once. If you re-geared it so that it would shift like the normal Vette (ie be in 4th or whatever at the end of the strip), it would hit 900 hp four times. Accelerating force is determined by hp and speed. The 1 gear Vette would be accelerating less at every point compared to the 4 gear Vette except at the very end of the drag strip because it would be making less hp than the 4 gear Vette at every point.

 

[ToreDL87]

You`d still be looking at high maintenance rates and thus costs and reliability, a race tuned 1600cc inline 4 engine @ 8000-9000 rpm is just about right for racing, and it`ll kick a stock honda vtec 1600cc`s arse (Anyone who knows why Vtec was actually created and what it does would know why) otherwise it wouldnt be called a race engine.


Of course 250cc engines and the likes can do 16000rpm and what not, I`ve seen 75cc mopeds that do the same but I let that out of the equation because of reasons I would have thought to be on the slightly obvious side

I dont mind if any one of you built a non turbo 1600cc high RPM (10000-12000 rpm) inline 4 Race engine, I`d love to see it on a 3 day track event, but imagine the track being 2-3km long, a conditioned driver should be able to round 200 laps a day (Including pit stops and breaks), thats a minimum of 1200km @ full throttle in 3 days, stock engines are already hard pressed right there..

Whats the one thing you gotta do to win a race? You have to finish the race..
Again I rest my case.

 

[PawnBoy]

Do Formula 1 engines count? The FIA regulations limit them to 18,000rpm (but if allowed the teams would run higher) and the engines are required to last more than one race weekend.

 

[Famine]

You`d still be looking at high maintenance rates and thus costs and reliability, a race tuned 1600cc inline 4 engine @ 8000-9000 rpm is just about right for racing, and it`ll kick a stock honda vtec 1600cc`s arse (Anyone who knows why Vtec was actually created and what it does would know why) otherwise it wouldnt be called a race engine.


Of course 250cc engines and the likes can do 16000rpm and what not, I`ve seen 75cc mopeds that do the same but I let that out of the equation because of reasons I would have thought to be on the slightly obvious side

I dont mind if any one of you built a non turbo 1600cc high RPM (10000-12000 rpm) inline 4 Race engine, I`d love to see it on a 3 day track event, but imagine the track being 2-3km long, a conditioned driver should be able to round 200 laps a day (Including pit stops and breaks), thats a minimum of 1200km @ full throttle in 3 days, stock engines are already hard pressed right there..

Whats the one thing you gotta do to win a race? You have to finish the race..
Again I rest my case.

Oddly, someone I know has paper-built a 10,000rpm 2.2 litre V6 to go in a road car - nasp to start with, but there's scope for an Eaton screw - as a hybrid of a few stock engines of varying capacities from the same range. On the various standard, production parts the math says 250hp nasp and with almost zero overlap the supercharged version should be a bit potent.

There's a couple of questions about the crank, but bench tests (not in that application - the original) have shown it can spin at 11k without tearing itself out of the case so it should be fine.

The creator of this engine is, fortunately, busy with some V8s at the moment so hasn't turned his focus onto this yet. I say "fortunately" as I know he'll want to put it into my "spare" road car in the absence of any better recipients.