Originally Posted by catm3
To me, crank numbers are worthless, and can be misleading. The E46 M3 and 335i put down fairly comparable rwhp numbers, yet their crank rating is 33hp different.
Reporting numbers from the crank or from the wheels provides different feedback to different people. Not to mention that the numbers significantly differ between automatic and manual transmissions. While power at the wheels may be all you are looking for, an engine tuner can find the power at the crank to be a more meaningful number.
When doing engine performance modeling through calculations the numbers only deal with what is happening in the engine. Adding in the drivetrain (meaning transmission, wheels, etc.) variables adds in unwanted uncertainties. I often crunch numbers to model how a turbocharger will perform on a particular engine. The more accurately I can model the numbers the more accurately I can predict how an engine will respond to a particular turbocharger. Having a simple dyno chart of an engine's output at the crank is one of the best tools I can have.
Plus since you mention the fact that while the E46 M3 and the 335i have similar outputs to the wheel but the difference gets larger when reported at the crank you can see right there where you can pick up some power to the wheels in the 335i. The 335i could benefit from a lighter flywheel, driveshaft, wheels, etc...