engine/spark knock

[SupraTitan]

I think alot of people are confusing pre ignition with detonation. The engine will not last long if deto is occuring, fragged pistons and or blown headgaskets usually occur soon after heavy deto occurs. On a naturally aspirated titan, you would have to have some really crappy fuel to get detonation. Pre ignition or pinging is typically harmless, just annoying.

[ablexus]

Originally Posted by SupraTitan

I think alot of people are confusing pre ignition with detonation. The engine will not last long if deto is occuring, fragged pistons and or blown headgaskets usually occur soon after heavy deto occurs. On a naturally aspirated titan, you would have to have some really crappy fuel to get detonation. Pre ignition or pinging is typically harmless, just annoying.

I'm pretty sure we're talking about detonation, here.

Knocking (also called pinging)— colloquially detonation—in internal combustion engines occurs when air/fuel mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. The engineered combusting process ceases, because of the explosion, before the optimum moment for the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber, creating a characteristic metallic "pinging" sound, and pressures increase catastrophically. It can range from hardly noticeable to complete engine destruction.

http://en.wikipedia.org/wiki/Engine_knocking

Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.


Mild or occasional detonation can occur in almost any engine and usually causes no harm. But prolonged or heavy detonation can be very damaging. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem.

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

DETONATION:

Also known as ping or spark knock, detonation takes place after the spark plug has fired and a portion of the air / fuel mixture has been consumed in the normal combustion process. As combustion progresses and octane quality is inadequate, the pressure and temperature in the combustion chamber increase to a point where the remaining unburned mixture is unstable. At that point, the remaining mixture self ignites, creating much higher pressure and temperature than would occur during normal combustion. The sound of detonation occures when the peak cylinder pressure takes place too early in the cycle. This causes vibration in the cylinder walls, resulting in ring seal loss, and excessive piston rock. Detonation can also overload the pistons, rings, wrist pin bushings, and rod bearings. Some engine damage can occur when detonation is mininal, but severe detonation can cause major damage.

PRE-IGNITION:

This phenomenon is just as its name implies that it takes place before ignition of the air / fuel mixture would normally occur (that is, before the spark plug fires). This condition is caused by a hot spot in the combustion chamber. It could be a piece of carbon, a hot spot on the exhaust valve, or from heat generated in the previous combustion stroke. Pre-Ignition is very likely to be destructive due to the very high cylinder pressure that occurs before the piston has reached top dead center. This condition can damage or destroy pistons, rings, bearings, crankshafts, and head gaskets.

Neither detonation nor Pre-Ignition is good for an engine. Detonation is likely to damage it, while Pre-Ignition can destroy it.

http://www.whitfieldoil.com/www/docs...ace-fuels.html

Andrew