15% is the standard rule of thumb for parasitic loss. It would be a little bit more for an auto. But a dyno is a dyno, there are many factors that go into producing a final RWHP. There is weather, temperature, mechanically variation on the dyno, mechanical tolerances in the particular engine.
But 15% is a decent guesstimate for what crank HP will translate to at the rear.
I don't think a percentage is an accurate rule of thumb for parasitic loss. Say you have an engine with 500 hp in a car and take that 15% parasitic loss, you have 425 to the wheels (75 hp loss). Now say you have a 1,000hp engine in the same car; taking that same 15%, you would have 850 to the wheels (150 hp loss). How did the same drivetrain just take 75 more hp to spin? Sent from AutoGuide.com App
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