SS RRR

I am wanting to ask those who may have opinions on this subject if you feel they are one in the same? During normal operation in a gasoline operated internal combustion engine does an air/fuel charge explode or combust at the time of ignition? Is there a difference? Can you describe the difference?
Also is there a difference between pre-ignition and detonation? If so, what is it?
I've read instances where people think explosion and combustion are one of the same. If you would like, please discuss...

SStrokerAce

It burns....

Gas doesn't explode, Nitro does.

Bret

HardcoreRM125

Detonation is the intake charge igniting BEFORE there is spark. This is caused by excessive heat and compression, kind of like how a diesel fuctions. It compresses and is so hot that it begins to burn before the spark, while the piston is still coming up to TDC. The opposing forces from the piston coming up, and the burning fuel ( Pressure ) pushing the piston down puts tons of stress on the rotating assembly, and can cause serious engine damage/failure.

As far as preignition goes, I am not really sure if it is the same thing as detonation, but the name would lead me to believe it is. It is igniting before the spark.

Bret ~ I sent you an email today

Injuneer

Combustion is a relatively slow process, compared to an "explosion". The flame front moves outward, radially from the spark plug. In a normal combustion chamber, with normal O2 concentrations, the flame front will probably move in the range of 20 - 150 ft/sec. As O2 content is increased (e.g. - using nitrous, or fuels that bring their own oxygen, like alcohols, nitromethane) the speed of combustion increases. The nitogen content fuel, like nitro methane also act more like "explosives" because the the intense energy released when the nitrogen bonds are broken.

Preignition, or "ping" results from the compression heat igniting the air/fuel mixture BEFORE the plug fires. Detonation, or knock is the result of chemical compounds formed AFTER the plug fires autoigniting, causing a second flame front in the combustion chamber. When the two flame fronts collide, you get a healthy pressure spike, and a lot of vibration, which decays very slowly.

SS RRR

Some good reading
http://en.wikipedia.org/wiki/Detonat...bustion_engine