no, you are talking about increasing the speed of the engine as a way of increasing power. It doesn't work that way. Could you spin an S2000 engine at 18,000 rpms and expect to make 480 hp? No. If you just increase the rpm of the engine, you are not increasing the amount of fuel and air combusting in an event. As I stated in my last post, increasing the max rpms merely increases the time spent in first gear - it doesn't increase acceleration, but lets you remain in first gear longer, accelerating harder than if you were in second.

Engines aren't pulleys. You don't make twice the power simply because you spin the engine twice as fast - things don't work that way. If you could keep the torque the same, you would double your hp numbers, but keeping torque constant as rpms climb is rather hard. Let's not even get into the difficulties of doubling the max rpms of a given engine at anything close to a reasonable cost. It would be more effective to add cylinders to increase the number of explosions per revolution, IMHO

 

what a load of crap. If you know an engine makes 200 hp, but not the rpm, you know nothing about its acceleration. It could make that 200 hp at 2,000, 4,000, or 10,000 rpms, and acceleration would be different for each, as torque output would change accordingly. In addition, in the real world, gearing would be different depending on the powerband and intended use of the vehicle, affecting acceleration rate.

 

Your handle says it all!

Really!

 

Your poll options do not answer the question you asked on a truly technical manner.

 

Right, that's why it's peak horsepower. I don't have too much experience with gas engines, but with electric motors the shape of the hp curve is about a semi-circle. It rises, peaks and then falls with rpm. Don't IC engines have a similar trend? I might be talking out of my ass

 

Not true.

In the modern car world, you can assume a few things. 1st gear is good for about 30 to 40 mph, 2nd geat 60-70, 3rd about 90, etc. etc. Obviously this is not 100% accurate - for example, the differences between 4, 5 and 6 speed gearboxes, and special cars like the McLaren F1 and Lamborghini Murcielago that can hit 60mph in 1st gear. Look at the '04 vs '03 S2000 comparison as well. But for most cars, particularly sports cars in the range we're talking about, that's generally a safe assumption.

Given that, if you tell me a car's weight and HP, I can tell you about how fast it'll be. 2800 lbs and 240hp, and it'll do about a 14 second quarter-mile. Doesn't matter if it's a 10,000 rpm, 125 lb-ft engine or a 2000 rpm, 630 lb-ft engine - assuming they are both geared to hit the same mph at the top of each gear.

It's all about drive-wheel torque. THAT is the force that turns into the linear force that accelerates the car. Given hp, you can make assumptions about the gearing and therefore derive approximate wheel torque. Given crank torque, you'll know the shape but not the magnitude of the acceleration profile.

 

F1 engines at 18,000rpm make significantly more HP than any other 3.0L engine out there. But they only make slightly more torque. So extending the rev range of an engine to increase its power output, while expensive, is an entirely legit way to get more air and fuel flowing through it and therefore achieve a greater power output. It's all about fuel utilized per unit time, not per spark ignition. Displacement and forced induction simply happen to be the easiest/cheapest methods to do that.

IMO, higher revs is certainly the most fun method.

 

Actually you can get a fairly good idea how quick a car is by weight and horsepower. Here's an example:

The cars and their lbs / hp (less is better):
Car................weight........horsepower....... #/hp (less is better)...........1/4 mile
S2000........... 2800 lbs....... 240 hp.................11.67........................14 .0-14.5
350Z..............3225 lbs........287 hp.................11.24........................13 .9-14.4
EVO...............3260 lbs....... 271 hp.................12.03........................13 .5-14.0
'04 Mustang.. 3347 lbs....... 260 hp.................12.87........................14 .3-14.8
'05 Mustang...3450 lbs........300 hp.................11.50........................14 .0-14.5

The #/hp is a very good estimate of performance. Any car that is within 1 #/hp is going to be a very close race. As you can see above, all the cars are within 1 #/hp and in the real world all of them are going to be a very good race. Some certainly have an advantage (350z, '05 Mustang) but all are close enough that it could easily come down to the driver. In the real world I've had a few races with an S2000 and 350z and both were dead even up to ~70 mph (I have an EVO). In fact the S2000 seemed to pull a few feet on me on every shift which would certainly be understandable given that the S2000 has a better power to weight ratio.

As a said before, all you need for a decent approximation is horsepower and weight. Why don't you need the rpm where peak horsepower is? because all manufacturers match the transmission to the engine. I've mathmatically proven on page 15 of this thread that with the ideal gearing, two cars with the same peak horsepower and different redlines have the same acceleration. So it's pretty safe to say that each car's transmission will take full advantage of it's power band. So in the end it's going to come down to horsepower and weight.

Obviously #/hp is not perfect. It doesn't take into consideration drivetrain, aerodynamics,etc. but it is a very good approximation.

But I'll leave it to you no-really, if you can find a car where the #/hp doesn't give a good approximation then I'll conceed that you need more information. And this must be a car that is mass produced. Not some stange kit car with no information on it or one that is known to be underrated like an SRT4 (rated 220 hp but probably closer to 250 hp).

 

Why not?

 

Production car valve trains can't spin that fast. You'll get valve float and bend every valve stem. F1 cars use a completely different valve trainthat allows them to spin to 18000 rpms. They also consist of extremely light metals and on average the engine lasts about 500 miles before a full rebuild...certainly not good enough for a street car that's required to last 100+k miles.