Quote:
Originally Posted by e1000
1. It's not "to the wheels". To the wheels is after gearing.
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"Rear Wheel Horsepower", RWHP, and "Rear Wheel Torque" RWTQ are standard terms across the industry, used to do equations like those below. I don't make the rules.
Quote:
Originally Posted by e1000
Go ask a physics person.
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Yep, I'm an engineer. I don't want another misplaced 1M/ M3 debate, but I will try to explain my comment as to why the 1M breaks the rear tires loose relatively easily.
The formula to calculate it yourself is as follows: Take the torque figure after driveline losses (otherwise known as that RWTQ number above), multiply it by the ratio of the gear you are in, then multiply that by the final drive ratio. This will give you in-gear torque. Example:
1M 1st gear:
360 lb-ft x 4.11 x 3.15 = 4667 lb-ft.
M3 DCT 1st gear:
255 lb-ft x 4.78 x 3.15 = 3844 lb-ft.
So in this example the 1M's peak twist is 21% higher than the M3, the car has roughly 100 lbs or 6% less weight over the same drive wheels and tires, so the car is going to break traction much more easily.
However this calculation is for
peak torque, and peak torque by itself doesn't tell us much about overall acceleration, which is what you're trying to get at. For that you need to know speed, weight and at higher speeds drag. To avoid a physics lecture, the short version is that higher in a gear, as the 1M's torque falls off, the M3 remains nearly constant, so higher
peak acceleration does not guarantee higher
average acceleration and hence that a car is faster at a given speed or overall. There is a lot on the topic already, perhaps you'd like to take it up in one of the other threads, such as:
http://www.1addicts.com/forums/showthread.php?t=668630