Originally Posted by oldford

It is my believe that the transmission loss is a fixed number of bhp, not a percentage.
I have tuned a lot of cars and usually had them on a rolling road before and after. The transmission loss was always almost the same (plus or minus 1 bhp).
Lets say I have a car with standard 300 bhp and 4-wheel drive. Put it on a rolling road and measure 200 bhp on the wheels and 100 bhp losses. Then I tune the engine to 600 bhp (supercharger, No2 injection, you name it) with same rev range as standard and measure it again. If the loss is 33%, I would now have 200 bhp loss. But the transmission has not changed. So, I would still measure the same 100 bhp loss.