[Garrett]

Originally Posted by Durbrain

I'm not confusing the issue. I'm not disagreeing with what you're saying. And yes, I know what 'acceleration' is - any junior high school student knows what that is!

But, I *am* pointing out that what you're saying is largely irrelevant when it comes to looking at the specs of a car.

No car's specifications come with a torque curve. The only two specifications car manufacturers give us is peak power and peak torque.

If we are to choose one which would best represent the performance of the car (ie the 'average' acceleration...since, as you said, acceleration is *not* constant throughout the rev range...unless there is a completely flat torque curve...which never happens) - then you need to look at power.

I'm not sure you understand the concept of 'average' acceleration (if you do, forgive me) - so let me explain it. If a car accelerates from 0 - 30 at say 2ms^2, then accelerates from 30-60 at say 4 ms^2, then the *average* acceleration from 0-60 is 3 ms^2. That is, even though the car never actually accelerated at 3 ms^2, the time it took for the car to accelerate from 0-60 is equivalent to the time it would have taken *if it were travelling at 3 ms^2 the entire time).

This *average* acceleration is what is important, when discussing the overall performance of a car. And *average* acceleration best correlates with the *peak power* of a car. Hence why *power* is the best marker of the performance of a car.

You seem fixated on the fact that the *instantaneous acceleration* (ie the exact acceleration at any point in time) exactly mirrors that of the torque curve. This is true. I am not disputing this. But it is useless information. It tells us very little!

If you read the torque curves of two cars, yes, of course you can tell me exactly when each car will accelerate at its maximum. But who cares?! You can't tell me which car is going to be able to perform better overall?

When people compare the performance of cars, they don't go "Oh, well my car peaks its acceleration from 2000-4000rpm, wow isn't that great?" No!! They go "My car does 0-60 in 5 seconds".

The torque curve is an interesting piece of information if you want to know how a car will feel like to drive. Ie will it feel linear (a flat torque curve, and hence relatively constant acceleration) or will it feel peaky (a torque curve that rises to a peak then drops, with mirroring acceleration rates). But it won't tell you how fast the car will go from 0-60, 0-100, 30-100 etc etc.

Yes..YES and YES. But NO !!!

I KNOW it's irrelevant. If I tell you that my car has 4 tires, that is also irrelevant, but is also TRUE.

Torque=Acceleration

Your trying to put words in my mouth and teach me something I am fully aware of. Also, your "intantanious acceleration" is not my words or my analogy. I'm talking about the RATE of acceleration. As infatesmol or irrelevant as it is in dealing with the overall acceleration of a car. Never-the-less, the rate of acceleration is fastest at the highest torque point within the engine. Albiet, minus anomolies such as torque converter, clutch and limited slip...etc.

Now there are many small discrepancies in CARS that will alter that formula somehwhat.... but those are irrelevant to the overall debate at hand. In which your in agreeance with me on.

"Average acceleration" was in quotes... because it was something you (or another said) Not my words. Meaning, but you can have an engine with a torque curve like a bell (Peaky) or one thats more smoother and more of a perfect curve like the top of a basketball.

If the bell curve has 400 ft-lbs and the Ball curve has 350 ft-lbs i would chose the Ball curve. Because overlaying the two, the ball curve has more torque when compairng their delta's.

*BUT THAT IS NOT THE TOPIC OF THIS DISCUSSION*

Just because I didn't discuss it earlier or add any other benifits from torque doesnt mean I'm unknowladgeable, I'm just trying to keep this debate on track... and if you havn't read this whole thread let me remind you what we were dealing with.

Originally Posted by Saintor

Turbo (x2) is a stupid stupid idea for only 300HP. Even Audi abandonned it. They just had to throw in the "old tech" M3 engine and they would got... 333HP. In the end, these double-turbo engines takes as much fuel as larger engines and they would have been better with a larger displacement at the beginning. I owned 2 turbo cars. Harder to resell at high mileage, too.

Crazy move from BMW.

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Originally Posted by Saintor

Completely FALSE. HP is what matter for acceleration. You can have a big engine with top torque figures that will be slow as hell. Not its definition, but HP shows how quickly an engine will change RPM under load.

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Originally Posted by Saintor

No, no, no, no.

Ever tried a 1.8T? 100% of torque at 1600rpm. I can tell you that at 1600rpm, this engine has no trust and not much happens under 2500-3000much

Power is what ultimately will determine acceleration, at any speed.

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Originally Posted by Saintor

No, I am not wrong. You are.

Don't believe one site because you'll get another one that says the contrary on this subject.

Fact is that an engine pulls quicker on peak HP over all gears, NOT on peak torque.

If you have an engine with the following specs, 200HP at 5400rpm and 200lbs.ft at 3500rpm. According your logic, you would have to shift to keep an average close on 3500rpm.

I can tell you right away that the guy shifting at redline, will get you easily, no context. Because he is optimising the average RPM close to the 5400rpm - at peak HP.

As for understanding torque, I am a registered professional mechanic engineer, thank you.

It is not for nothing that in track races, tech people focus ONLY on HP figures, much much less on torque. Not a mistake.

Get it.

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Originally Posted by Saintor

Don't make stupid assumption and imbecile statements. In an engine, torque is NOTHING without RPM. Both torque *AND* RPM define HP. Over gears and the range of RPM, HP is the determinant factor for acceleration.

Again, the one who is lost is not the one you thought.

So, after all that it's obvious he doesnt understand torque. I know what torque is and does... but I am trying to show him ONE simple thing that almost un-debatable. Once he understand or ackowldge it, then we can go on to educate him the other aspects of it.




-Garrett