What's a reasonable estimate for drivetrain loss on our cars?
The general internet consensus is 20-25% loss for a 4WD car.
I assume a dogbox or similar and pretty heavy clutches, super tight diffs and the like would lower this loss somewhat? Would they stay relatively constant until you hit the big 7, 8, 9, 1000 hp ranges?
Some hard numbers:
Pot dynoed his (otherwise) stock VR4 at 174 WHP (13.5 PSI), where as your stock cars were 195 BHP (7 psi?) at the factory. These numbers can't be compared directly but what if we bump up the stock figure? If we assume a very generous 10BHP per PSI we would be looking at 174WHP vs 255 BHP and 32% drive train loss, while 174 WHP with 25% loss is 232 BHP...
The Bonneville land speed VR4 claims around 15% - which leads me to believe it could be a 2WD Galant or just a highly polished speed machine?
I've read a stock 3000GT has about 25%. The Nissan GT-R has been measured at 17% drivetrain drag AND published with understated power figures. An 1100 mile Evo X has about 16%, Evo IX around 20%, Evo VIII around 20-25% (depending on year and assuming constant power level).
Food for thought:
(the first two cars that turned up in the search)
Garfield Wright put down 361 Front Wheel HP, while Nartanian put down 301 All Wheel HP. In theory Garfield only has 10-15% drivetrain loss and Nartanian has around 20-25% (or whatever value we come up with).
This gives us 401-425 BHP vs 376-401 BHP