What causes "pinging"?

[HIGHPLAINSDRIFTER]

Hey all, I have been reading alot of the threads lately about timing and how to adjust it.  Some of them mention "pinging". I have heard that "pinging" sound coming from my Harley motor before, but never from a truck.  With my bike , if I just add a little octane booster or fill up with hight test it goes away.  I understand that the cylinder is firing before the piston is at TDC, but what actually cause's the noise that you hear.  Basically, what is banging on what?  Thanks for helping me understand this a little better.

[78 Chevyrado]

http://www.misterfixit.com/deton.htm

[HIGHPLAINSDRIFTER]

That was perfect, thanks!

[VileZambonie]

Pinging can be caused by many reasons.

Pre-ignition and detonation are essentially two different things that make the same sound you hear.

Detonation is when the air fuel mixture explodes rather than combusts normally.

Pre-ignition is when the air fuel mixture ignites prematurely. Pre-ignition typically causes detonation.

The sound you hear is an audible "ping" typically caused by the result of two flame fronts that collide during combustion. I've explained this in much greater detail if you do a search.

[HIGHPLAINSDRIFTER]

thanks Vile, I did a search before I posted but I looked for pinging.  I will try looking for detonation and pre ingnition.  Thanks again.