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Just one part taken out of the mess "If we wait to retard timing until the RPM is quite high, we risk knock and engine damage." And did you not see the paragraph from Bell's book on Forced Induction (actually, I found hundred of references in google as well afterwards): Forgive the typos, I think Seb copied it quickly: "when the chage temp. is excessive, what should have been a progressive burn near TDC becomes a violnet explosion- detonation. The combustion space is small, piston acceleration is slow, so piston, rings, head gasket, valves, spark plug, cyl. walls, bearings and crankshaft cop a good hammering. Enter the savior for many- spark retard. Let me make this clear, optimum timing is just that - it is the best. Any deviation from that hurst performance, but, and this is why sprak retard is a crutch fr so many, it can save engines from being wrecked, HOWEVER, it too can be a self-perpetuating problem, even an engine destryoer, combustion slows so much that as the exhaust valves open, the fire is still going, consuming fuel. This increases exhaust valve temps as the fire races out past the valves into the exhaust manifold. The exhaust side of the combustion chamber becomes hotter too, as does the piston crown. Soon the inlet valve opens to admit the fresh fuel/air charge, but all these hot parts quickly heat the inflowing charge. It quickly expands, filling the cylinder w/ a low density chrge that will result in a poor power outcome at best. At worst, combustion has continued so late on the down stroke that the piston crown, exhaust valve and combustion chamber have had insufficient time to cool before the fresh charge enters the cylinder. This retianed heat is enough to get combustion started long before the plug fires. The intense heat resulting from pre-ignition is much like a blow torch and melts through the crown of the piston."
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03:03:40 12/30/03
