Well, strictly speaking an internal combustion engine "detonates" every time the fuel mixture ignites.

Many people don't realize that the combustion flame front normally do not come into contact with the piston. A thin layer of insulating air protects the piston crown from the extreme temp of the flame front, which can easily melt the piston alloy. When the flame front does come into contact with the piston, the engine is said to have "detonated" or "pinged". The result could be mild pitting on the piston crown all the way to burning a hole right through it.

Detonation can be caused by many different reasons, including but not limited to:

mixture too lean.
ambient temp too high.
fuel "octane" too low (i.e. fuel that is too fast burning)
ignition timing too advanced
engine load too high.
CR too high (too much carbon deposit can also cause the effective CR to rise)

Severe and/or prolonged detonation can cause serious internal damage to the engine, but it is unlikely to "explode" into a million pieces. The typical IC engine is designed to withstand tremendous amounts of internal pressure building during the normal combustion process.