Since this discussion is ranging all over the place...
I've never understood how parasitic loss through the drivetrain could be a percentage. That would mean a really powerful engine would lose more power than a less powerful engine turning the same components at the same RPM.
A transmission should take a given amount of power to spin it at a given RPM. The internal friction would not change based on the engine in front of it. Same with differential and all the other sources of losses such as the axle bearings, u-joint bearings, tire rolling resistance, etc.
So let's say we have an engine that puts down 150 HP at 5000 RPM on an engine dyno. Put it in the vehicle and you're seeing 100 HP at the wheels - you have 50 HP of loss in your drivetrain at 5000 RPM. If you put an engine that is making 400 HP at the crank at 5000 RPM in the same car you should see 350 at the wheels.
Can someone explain how that line of reasoning is wrong?
