9cc makes it about a .55 cubic inch sized engine. So isn't all that far away from being a regular .60 engine. My example of the NGH 9cc engine is turning a 11x6 prop at about 11,500 rpms. But it is still relatively new and being run in still. I haven't tried a 11x7 yet. When I last tached a Fox .45 glow RC engine, I was getting around 12,500 RPMs with it using a 11x6 prop and its stock muffler. So I feel the gasoline 9cc engine runs about like a 40 to .45 glow engine. Now the NGH engine might do better if I changed the ignition timing a little, maybe advance it very slightly or or less. But since it was running pretty good like it is, I didn't try that approach.

I have myNGH engine idling as low as 2,500 to 2,600 rpms OK. below that and the engine tends to develop too much of a surge like effect to it. Sort of like a old time WWI fighter plane with the pilot cutting the ignition on and off to taxi the plane around. It might be the RCExl ignition with the advance RPMs trip point set a little too low or high thus it puts the engine on the edge of advancing or retarding the ignition around that RPM speed.