Thread: M3 Dynotest
View Single Post
      09-08-2007, 09:10 PM   #20
Lieutenant General
swamp2's Avatar

Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

iTrader: (1)

Sort of

Originally Posted by chonko View Post
Drive train losses are not a fixed percentage, but rather fixed number.
Parasitic Torque losses= Friction coefficient X Rotating Mass X Radius.
Frictional coefficient is higher at lower RPM, and does change with RPM.
By using lighter materials in the transmission, you can reduce the drive-train losses.

Audi has higher losses because the rotating mass (Quattro drive train) is more than the that o RWD system.
For one you are contradicting yourself here, you say the loss is a fixed number, which is false, then you say in the formula is it a function of rpm, which is correct. Your formula may have some correct features but is wrong as well, a simple check of the units will tell you that (watts is not equal to mass x distance). An AWD has more losses becuase of the number of lossy interfaces, gear interfaces and bearings, etc, as well as the larger rotating mass involved.