ORIGINAL: molokaiboy
ORIGINAL: ThumbSkull
The 91FX is not a great 3D engine unless you can find a 3 needle carb like the 7L (rare).
Is this because this engines power is mostly in the higher end of the throttle range( 3/4 and above) and many 3D planes utilize the lower throttle range (0- 3/4), and with only a 2 needle carb its harder to tune the midrange where most 3D pilots use?
In a nutshell, it has poor mid-range performance and swings a small prop.
ORIGINAL: molokaiboy
Is 4 stroke preferred because of their ability to make power at a lower rpm with more torque swinging a bigger prop moving more air, instead of moving air faster?
It's partly that and the 4-stroke will change the speed of the plane quicker because of the bigger prop.