MVVS 77 Prop Choice (no pipe)/FAI fuel consumption
 

I would appreciate your suggestions on prop choice and fuel consumption for the MVVS 77 running without a pipe (pitts muffler).

This is the old style (with separate prop shaft) but with the upgraded nozzle and idle needle (#s 0253 & 0232)

I will run FAI fuel, no nitro, and use the MVVS plug that came with the engine.

Instructions from the MVVS website (for the newer version of the 77) recommend 13 x 7, 13 x 9 or 14 x 7, and "min RpM 10,000"
noting that actual rpm's will vary with prop design and silencer used, and, they add
"Use lighter propellers with standard silencers so that the engine will be able to reach at least the Rpm listed above.)

I plan to use wooden props, not APCs.

I understand there is a significant drop in performance without a tuned exhaust, but if you have had experience with this engine, what size prop should I consider to achieve the 10K rpm on no nitro fuel?

Secondly, does the lack of nitro mean increased fuel consumption? Is the difference enough that I should go with a larger tank than I would use with 15% nitro?

Hi!
Less nitro gives longer duration (engine runs)!
I would go with a 12x7 or 13x5 for most low winged sport airplanes. 14x4, 14x5 for high winged,slow flying planes like a CUB.
Best props performance vise are German made "Graupner G-Sonic " British "RAM" and APC. Wooden props are not that good performance vise compared to those I mentioned but...if you file them thinner and modify them they can be rather good too.

Thanks for the info.

A few years back I decided to go all wood because they are more likely to break, say, if they hit flesh. I give up some rpms, back that's okay by me.