I got my TT39 this month and have ran it about 4 tanks. This engine is very strong even when ran rich with 15% I put it in my Quick 30 Pro and this thing is awesome. I have always used OS 32's on my heli's, but after using the TT39 I sold all my OS engines. I have another TT39 on the way right now. Best power upgrade without the hassle and price of changing to a 46/50.