A dedicated Diesel will burn noticeably less fuel than a glow of the same horsepower.
Unfortunately our converted engines are optimised for glow use. The carb, transfer passages, and timing aren't ideal. This combined with the fact that we are actually producing more horsepower than the engine would on glow, means that we don't see quite as good fuel economy as we otherwise would.
I agree with Tim and Dave, the best prop for your model and engine is likely to be bigger than the engine would use as a glow (most likely 10X6), and best performance is likely to be at a lower RPM, so 11X6 or 7, or 12X6 might be about right. Like all model and engine combinations, it depends on the model and your flying requirements. Props are cheap(ish) so grab a few and try them out.
Are you worried about the tank in your model? As I said a tank sized for a .25 to .30 glow should be fine for a .40 Diesel (especially if the extra power lets you throttle back a bit), so I'd be tempted to try it first. You will need to check that the tank plumbing (bung) is compatible with Diesel fuel of course.
Don't listen to Tim when he says he's a Diesel newby, he know his stuff, as do Dave FDF and Lou.
Dave H
Last edited by gerryndennis; 02-05-2016 at 12:11 AM.