Tire shop horror story! Please help!
#44
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Originally Posted by Elistan,Jan 15 2008, 10:56 AM
Slight nitpick - it's an unctrolled combustion before the spark plug fires, which may or may not be at TDC.
Otherwise
Otherwise
The spark plug ignites the mixture adjacent to the electrode. The burning mixture expands as the flame front moves away from the spark plug, compressing unburned mixture in front of the flame front. If the octane of the fuel is too low (or there's a piece of carbon that forms a hot spot in the unburned gases), a second ignition takes place some distance in front of the flame front. Now you have two flame fronts that collide. That's detonation.
The compression ignition in a gasoline engine is almost always caused by the compression of the unburned mixture as the flame propagates through the cylinder. If detonation were occuring before the spark, then how could retarding the timing (making the spark later) mitigate the situation.
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John_Z
California - Southern California S2000 Owners
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08-10-2003 05:49 PM