Preignition or detination?

Jeff65 · 09-10-2002, 10:21 AM

Low speed detonation is usually heard as engine knock. Making the fuel-air ratio richer, increasing the octane of the gas used, and retarding the timing all contribute to eliminating knock.

Did you hurt the engine. Almost certainly not because if you had done so, the engine would now be blowing black smoke badly.

High speed detonation is a lot worse because it isn't as easily heard and if allowed to continue, will eventually break something in the engine, usually a piston. If you see a piston to which this is happened you'll see a hole burned in its top (completely through the metal). When the hole breaks through, black smoke ensues (blown engine).

If you can hear the knock, ensure you take action to eliminate it from being continuous. A small amount of pinging on a hill is not likely to damage the engine but if you hear it, let off on the gas and take it easy until the engine stops pinging. If its a nuisance, then retune the engine or use higher octane gas.

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09-10-2002, 10:21 AM	#2
Jeff65 Registered Member Join Date: Jul 2002 Location: Oklahoma City Posts: 208	Low speed detonation is usually heard as engine knock. Making the fuel-air ratio richer, increasing the octane of the gas used, and retarding the timing all contribute to eliminating knock. Did you hurt the engine. Almost certainly not because if you had done so, the engine would now be blowing black smoke badly. High speed detonation is a lot worse because it isn't as easily heard and if allowed to continue, will eventually break something in the engine, usually a piston. If you see a piston to which this is happened you'll see a hole burned in its top (completely through the metal). When the hole breaks through, black smoke ensues (blown engine). If you can hear the knock, ensure you take action to eliminate it from being continuous. A small amount of pinging on a hill is not likely to damage the engine but if you hear it, let off on the gas and take it easy until the engine stops pinging. If its a nuisance, then retune the engine or use higher octane gas.