This has recently started to bug me. I'm gonna post it to several boards and see what it stirrs up. Should make for interesting conversation anyway.
Most people, when refering to rear wheel horsepower claims v. flywheel claims, will say there is anywhere from 15-30% driveline, parasitic loss. What bugs me is, how can we state this as a percentage. Assuming a Miata motor makes 100hp at the flywheel (easy math number, give me a break :)) and it's drivetrain saps 30%, we should get 70hp at the rear wheels. Now let's pull the I4 and drop in a small block Ford tuned to 300hp at the flywheel. It magically bolts to the Miata driveline. What will RWHP be? It cost the I4 30hp to turn it. If it only costs the V8 30hp we end up with 270 rear wheel hp and about 90% efficiency. If the drivetrain is said to be 70% efficient, how can it make the V8 waste 60hp more than the I4? It sould only take a given amount of hp to turn a drivetrain to a given speed. What am I missing?
Chris
