Detonation is the silent killer. It's a good idea when experimenting with different nitro %'s to take the head off an check the top of the piston often while going through the transition. Another tell tale sign is if when you switch and re-tune obviously that the motor runs a bit hot- then its probably detonating as well. Most race engines are shimmed from the factory to run at 25% nitro max as that is the max they are allowed to run in Europe. So I made it easy on myself and just run Trinity MHP 25% blend as does Byrons 2500.