I'm also no expert, but I thought that "detonation" in a gas engine just meant that there was too much fuel being injected, when the engine is at too low revs, so the piston can't move quickly enough to absorb the expansion and convert it to spinning the crankshaft - very similar to if the timing of the spark was too early.

Nothing to do with a transition to high explosive, although it will destroy an engine just the same.