You need to choose a prop based on your specific conditions and fuel choices.

The engine for best performance should run between about 9000 and 9500rpm. If you are going to be flying 3D the upper end of the RPM range is better as the engine will spool up better. This will give better response in a 3D mode. I would say 3D try to run it 9400 to 9800 and not over 10K.

This assumes that in a 3D application the engine will not running at full power for extended periods of time and the majority of your flying will be done at lower power settings.

If you are a firewall and forget it pilot like say somebody that is flying a scale model and making low passes and cruising at High power and High speed, I would tend to run it down in the 9000 to 9400 range. But not below about say 8800.

These range of power are what the engine is designed and timing is set for. Therefore the power band is in the sweet spot.

If you are not turning these rpms then make a prop change or a fuel change to get there.

I use the 30% Cool Power Heli fuel a 110S on a 15-10 prop turns up at about 9200. This is with my conditions PHX, AZ dry air, about 1200ft of elevation. If I got to Colorado at 5000ft I would expect to reduce the prop load to say a 15-8 for about the same performance. Go to say North Carolina with a Hot Humid day I would say the same thing probably a 15-8 would be the choice.

You have the 110FZ and not the 110S so you are are going to be down a little power to my setup. Maybe a 14-12 or 14-11 might be a good choice for you. A 15-8 could be good or even the 16-6W. Its all going to depend on what you like. I would say run it the way you have it on the 20-20 fuel and see where your rpms are. The going to 30% you will need maybe one size up on the prop if you are hitting the rpm range. One size means one pitch and or one diameter. Usually not both...Also the weight of the prop will play a role as well. A W or wide blade will be heavier and not only that much more load. A 16" prop will be heavier than the 15" prop. Often going up in Dia. will need a reduction in pitch. Say from a 15-10 to a 16-8 or 16-9 will load about the same.

Every Model is going to respond a bit differently to a given prop. You need to find a prop that works best on your model. This is why they make so many choices.


Ok here is a little formula that can help when changing props. It only works a little to compare props...prop efficiencies and lots of other factors will play a role. This will give you some idea of how the engine might respond. Its not science but can help in choosing. If you multiply the diam times the pitch. A 15-10 is "150" a 16-9 is "144" The props will be close to the same rpm....but the 16-9 should be a little slower. A 14-12 is "168" should be a little more load on the engine and a little faster.

Remember in doing this it only works as a relative thing and you can only use it to compare in close prop sizes. Higher diameters will result in higher loads due to the mass of the prop and smaller diameters can turn slightly larger bites or pitches do to their smaller mass.

Troy Newman
Team YS