Originally Posted by UdubBadger
isn't rwd drivetrain loss more like 10-12% and awd closer to 20%?
From what I've heard, it's impossible to get a 10% drivetrain loss. A manual, rear-wheel drive car can get as low as 12-15%. Automatics increase drivetrain loss slightly. And, lastly, AWD cars are around 18-20%.
The standard for most dynos I've seen is 15%, but it's important to remember that multiplying by 1.15 and dividing by 0.85 are not the same thing.
275whp x 1.15 = 316 crank hp
275whp / 0.85 = 323 crank hp
All of that being said, dynos should only really be used to quantify the change in horsepower for a specific car, on a specific dyno, on a specific day. For example, a stock vs tuned 335i. It's difficult to compare different cars through a dyno sheet (the variance that people got with the N20 328i dynos shows that).