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dfink,
You have to separate what happens at light load, part throttle cruise and what happens at WOT under load because they are very different states. One of the hardest thing for a first time tuner to understand is that idle conditions, where most of us started messing with engines, setting timing and twiddling idle screws, is a very small part of the picture and almost meaningless. All you want from an idle is the minimum rpm to prevent stalling. A road engine spends 85% of it's time under 30% load, most of the time is spent accelerating, decelerating and at a steady cruise. AFR's are not static and even the most sophisticated system can only dither the mixture around a target. Detonation only occurs at under high load, usually WOT around peak VE and is meaningless at idle or part throttle cruise. It is a pressure spike from spontaneous combustion of the fuel and cylinder pressure is a function of filling and throttle angle. You are not worried about detonation at 15% throttle. If you are looking for max efficiency, you want to run leaner than 14.7 : 1 with much more timing than 30BTDC under light load. Are you running a cat and do you have closed loop control ?
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Paul
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