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Originally Posted by LarThaL
As most of you know, torque and hp are not completely independent of each other. Hp is actually a mathematical calculation based on torque and engine speed. Most turbo motors, make "big torque", but are limited in their engine speed and their ability to produce that torque for any length of time. Hence the feeling that they "run out of breath" at high rpms. This is especially true for the smaller turbos that most manufacturers use to spool up quickly. Bigger turbos of course, suffer from more turbo lag, and are less beneficial off the line, and lead to a very surging type of power delivery. The M3 produces "only" 295lb ft of torque, but it can keep producing near that level of torque over a huge rev range.
When tuners modify a turbo motor ECU to give more boost, you will notice that this always results a greater peak torque, but that peak torque is very short lived. It goes back to that old notion of "the area under the curve". The M3 can keep making torque even at high rpms, hence the high calculated hp.
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Said best right here.
The best way horsepower vs torque was explained to me was: "Horsepower = Torque * Engine Speed"
And as far as performance of the M3 engine, it certainly is under-rated if you just look at the peak power of it. It is very smooth and delivers that power over a much longer period of time.
The Math gurus need to crunch a new formula to rate an engine which incorporates how much power was generated over a given amount of time. Maybe some kind of weighted horsepower figure.