I've heard of engines doing this for various reasons, like not having the right glow plug and fuel, etc. But what is it exactly? Does the engines really explode everywhere? And if so, how forceful is it and how far is the blast radius? I want to know this for my own safety as well as just plain curiousity. Thanks.

I see the results inside Super Tigers. There will be pits in the top of the piston towards the exhaust and pits in the head around the glow plug.

Jim

Detonation is normally the result of two flame fronts colliding in the combustion chamber, one flame front started by the glow glow plug, the other started by a hot spot in the engine or the increased pressure and temperature from the combustion process and a lean fast burn condition. The blast radius averages around 3/8 of an inch and is forceful enough to throw props off the engine and stop the engine dead in its tracks and sometimes bend rods, also on occasion blows the insulation out from around the post on the glow plug, Tower plugs and such.

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.

In model engines, predentonation can be caused by any one of the following or a combination of them; to high a compression,to hot a glo plug, to much nitro.