Panicosc,

I have the Evolution .61NT engine myself. I haven't done any scietific comparison between this engine and OS .61 FX for ex., but my impression is that it has a good deal of power, but not as much as the FX series. However, i think the engine is a good choice if you're not on the limit with power. With the right prop and 10% nitro it will pull well. Other highlights with this engine is that i have never had an engine which is easier to maintain. I put the engine in the aircraft, flipped the prop two times against compression and it started, ran perfect, never touch anything since.

Rgds
Oistein