ORIGINAL: Phil Cole
One of the best places to resolve this sort of question is
www.rcfaq.com.
A look at the RPM data base will show that the 25-30 cc engines all seem to produce their maximum power around 9000 RPM.
This is true but remember that all engines produce the most power at higher RPM's. For aerobatics and especially 3D, what really matters is the way it delivers torque. And the Moki has a nice flat torque curve (not peaky). Check out the following graph of the Moki 2.10 which is very close to the 1.80. Notice the torque between 6400 and 9400. It peaks at 8000 RPM. That is where the most usable TORQUE is for 3D or other aerobatics. The HP peaks out at about 9600 RPM but the torque falls off and this is not usable torque for aerobatics (bad acceleration). You want your peak RPM to happen very close to your peak torque for the best transition (= best acceleration). That would be around 8000 for the Moki 2.10. The 1.80 would be around 8400 RPM IMO.
So my experience is that the Moki is a very good glow engine for aerobatics. The 4-strokes have even better torque delivery but that don't have the brute power of the Moki and use a lot of expensive fuel.