ORIGINAL: Sport_Pilot
If you are getting the same amount of thrust, with a less efficient prop, then I agree, the engine is doing more work.
No work is the actual movement of air, not turbulance, not the energy the engine is putting out. We are talking about prop efficiency, not engine's. I was not talking about more thrust with a less efficient prop, but more thrust with a more efficient prop, with pitch and size (diameter and area) the same then a more efficient prop with create more thrust and this will cause the engine to slow down. Even though you may streamline the prop the engine will slow down if you do it right but it will push more air.