It's not easy to build both thin and light...then hope that it's strong enough.
The prop, engine and plane all have to compliment one another with these specialized engines. The speed engine is like a spoiled, bratty rich kid who dictates to his friends [in this case the prop and the plane] exactly what works with him and nothing else will do.
The smaller the engine, the more exacting this 3 way relationship tends to be.
Not only will the NR.15 act like a "spoiled rich kid", but as you already know it is also a spoiled FAT kid.
Without any hands on experience with the NR.15, I might be over-blowing what I think about it.
It's just that car engines work with much less load, so the designers can give them lots of exhaust timing to produce super high RPM without worrying about the loss of torque. If you can work it into your busy schedule, get it running [singing] happily with a few "target" props to play with just to see what size prop it is capable of turning in it's designed RPM range.
I've been curious about these engines but have never heard any "real world" feedback. The North American Speed Society" [NASS] is all about C/L Speed and they've most likely got some guys at that forum who can give you as much info as you need. They've always been very helpful with me and generous with their time.
Last edited by combatpigg; 11-15-2013 at 03:16 PM.