TattooTears

I hear this used a lot and I think it has to do with not using a high enough octane fuel on modded cars, but that all I know (or at least think I know about it).

HRnB

Pinging, your car keeps running when you turn off the ignition, etc. etc.

Timing and or incorrect air/fuel mixture usally.

Guest

Pinging and knocking is when your car detonates before Top dead center.

NOS/MAN

WHEN THE FUEL IS LIGHT BEFORE THE RIGHT TIME....BEFORE TOP DEAD CENTER,,,

luckythirteen13

having your timing set too far advanced or too low of an octane or a combination of the two will cause early detination

callmecobra

with out detonation, an engine would not run! what you are thinking about is pre-detonation. it is caused when to low of an octane is used, and the gas ignites from heat caused by pressure. the higher the octane rating, the greater its ability to resist pre-detonation

FoxGT

You do know an engine will run if it fires before TDC right?

BTW, I came across this a while back & thought it might be of interest to someone.
http://www.openminds.net/avalanche/octaneboost.htm

Guest

Yes, it just depends on the timing and the car. Let me clarify. Pinging and knocking is when the air and fuel combust in the chamber BEFORE the spark plug ignites it on the compression stroke.

NA cars will run the spark just before TDC, but FI cars usually run a more retarded timing, at or slightly after TDC.

roundman

You got it wrong 2000Si, most all internal combustion engines using gasoline for fuel have the timing system ignite the air/fuel mixture before top dead center, not after, for the best performance and efficiency. Once the engine is off idle, the timing advance systems will advance the timing to around 30 degrees BTDC so the mixture has time to begin to burn and therefore it can exert the maximum pressure on the compression stroke. In normal internal combustion, there is a rapid burning of the fuel/air mixture which releashes the energy in the fuel, not a detonation which occurs almost instantaneously. Pre-ignition is a better term to use for when the mixture is ignited before the spark plug fires. When the mixture ignites prematurely, the rapid combustion pressures can cause damage to pistons and bearings because they are trying to force the piston back down before it has gone past TDC on the compression stroke.

mkspeed26

damn, you took the words right out of my mouth. i have always been tought of it as pre-ignition, or the combusting of gas before the spark plug fires. thats why race gas is so high of octane. they want to run the most compression possible without blowing the gaskets (or engine, for that matter) because high compression = high power, but with that high compression you need higher octane. btw- higher octane fuel burns slower, giving the piston more time to reach the spark plug firing.