[ivymike1031]

perhaps you should look it up too. As far as I can tell, you've half-described pre-ignition, and half-described autoignition (knock). They're not the same, although preignition can lead to knock.

To summarize (and you should still look up more info), detonation occurs when the pressure & temperature within the cylinder get high enough to cause unburned charge to autoignite (compression-ignite). This auto-ignited charge burns simultaneously (instead of a little at a time), and a huge pressure spike results. This can be caused by a number of things, such as:
* spark timing that's too far advanced (fuel starts burning too early, and the pressure gets too high near TDC)
* compression ratio that's too high (cyl pressure gets too high on compression)
* too much boost (cyl pressure gets too high)
* poor charge cooling (cyl temp gets too high)
* low-octane fuel (octane rating reflects a fuels ability to resist knock)