ORIGINAL: Switch_639
on my 91fx... i am not getting the rpm that i would like to get with a 13x8 prop... this is recommended prop... what would happen if I go to lower prop like a 12x8 or so? would it have too much revs? is it bad to under prop an engine but still tach below the max rpm of the manufacturer? I want to get closer to 15K rpm... I am using the stock muffler which came with the engine...
You
SHOULD BE OK. You need to be sure you are
AT LEAST 500 rpm under max rpm (800 - 1,000 rpm would be better).
The reason is that the engine is going to "unload" in the air and your max rpms will increase.
You don't say how you want to fly the plane. If you are doing sport/scale flying you may want to try a 13x5 or 6 - if you will be doing 3D try a 13x4.