Several messages have touched on this point. One of the most important factors in prop selection is that it match the needs of the aircraft and your style of flying. To see how large a prop your Diesel will turn is like the guy with the glow engine that wants to see how fast the engine will turn on a small prop, even tho that prop would be impractical on anything but a racer - maybe. A large diameter slow-turning prop might fit a slow flying aircraft just fine - or maybe not.

For example, a fellow at our field has an Extra 300 with an OS90 on glow that flies well. He converted the engine to glow and tried flying on larger props to get better fuel efficiency. He discovered that the aircraft could not move fast enough at the lower prop speeds to do much more than circle the field. The best he could do was to use the same prop he was using on glow at roughly the same RPM and the about the same fuel consumption. No gain there. The power requirements of the aircraft were not compatible with the benefits of Diesel operation.

I am most interested in a Diesel engine where I want to swing a somewhat larger diameter prop than a glow engine can handle because it better fits the aircraft design. Generating a power or torque curve for the engine would be very helpful here.

derf