Also, unlike normal combustion, detonation is rather violent. Normally, when the spark plug sparks it creates a small and slow-moving flame throughout the combustion chamber. This flame expands so slowly, in fact, that the piston would be at the bottom of its stroke by the time this flame managed to burn everything. Fortunately, the flame is hot, so after a very short time the heat from it causes the rest of the gas to ignite and you get a complete combustion. However, when detonation occurs, usually it's because there's just flat-out enough heat in the combustion chamber to ignite the gas in this manner, BEFORE the spark plug gets a chance to do anything. So instead of a slow burn that shoves the piston down, when your engine is pinging you just get a big bang that puts major stress on all the parts in your engine, and loses you power. And as if that weren't bad enough, pinging creates more heat which makes the engine more likely to ping on the next cycle!
