never mind the usual maintenance and mechanical related failures, based on my experience (more with boost than N20), there are only a few things that can **** an power-adder engine. since boost and N20 really do the same thing, add oxygen to the mix (albeit in different ways), the symptoms of failure are the same. also any power-adder engine should run the highest octane fuel they can get, or run a detonation suppressant like water/alky injection, so this is not a factor in my mind.
1. going lean and getting it started knocking/detonating (audible or not) and chipping the edge of the piston, I think most N20 and turbo failures we see on this forum fall into this category, whether they admit to it or not. this is a tuning and fuel supply issue.
2. running something too hot, like a spark plug that is too hot a heat range, preigniting it, and melting a piston or exhaust valve.
to counteract item #1 you need a wide band O2 sensor and make sure you run sufficiently 'enriched' to prevent from going lean, that includes having a fuel system that will keep up. the cure for #2 is more dicey, of course you can start tuning with a really cold spark plug, but sometimes metal burrs or built up carbon can cause preignition, its a hard one to pin down because you really have to be pushing hard to preignite an safe, but high powered, engine combination. true preignition is very sporadic in nature.
