Originally Posted by
1QwkSport2.5r
The only real method I have at my disposal to determine power production of an engine is how fast it will turn the propeller. I have no way of measuring the HP or torque of the engine except through how the engine turns the prop. If an engine turns 200rpm faster and burns 10% more fuel, it wouldn't be worth it to me. 400-500rpm would be more "worth it" in my eyes.
I do not doubt what you're saying though.
How much more torque required would depend on the prop and the initial speed, those were not exact numbers I was quoting, there is at least one spread sheet and some programs out there that can tell you what the HP is when spinning a certain prop at whatever RPM, and increasing the RPM will increase the HP well above the percentage of speed increase. And I notice a substantial performance increase with just a 300 RPM increase with a prop turning about 10,000 RPM.