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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Advance
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<blockquote data-quote="MarBl" data-source="post: 128953" data-attributes="member: 4437"><p>It should be pointed out, that on most engines advancing the ignition is done not only because of power gain, but of heat reduction. In general, the more the ignition is retarded the hotter the engine runs.</p><p>If you have an ignition time intervall that delivers more or less constant power, you choose the most advanved ignition point to get the thermal optimum. </p><p>Now of course high speed pinging/knocking has to be avoided at all cost, so that sets an upper limit. But you want to run the engine close to that point.</p><p>That effect has not to be confused with the retarding of the ignition in a twin spark system. Because of the two ignitions on opposite sides of the combustion chamber the mixture is burnt much faster overall (but still in a controlled way). </p><p>One other advantage of a twin spark system is the elimination of ignition induced pinging. A weak spark (and/or slow burning mixture) in a big chamber (500cc and above) can lead to the effect, that the (pressure) shock wave of the ignition starts an uncontrolled, compression induced detonation somewhere else. You dont want that. You want the whole mixture being ignited by the flame front, not by pressure increase.</p></blockquote><p></p>
[QUOTE="MarBl, post: 128953, member: 4437"] It should be pointed out, that on most engines advancing the ignition is done not only because of power gain, but of heat reduction. In general, the more the ignition is retarded the hotter the engine runs. If you have an ignition time intervall that delivers more or less constant power, you choose the most advanved ignition point to get the thermal optimum. Now of course high speed pinging/knocking has to be avoided at all cost, so that sets an upper limit. But you want to run the engine close to that point. That effect has not to be confused with the retarding of the ignition in a twin spark system. Because of the two ignitions on opposite sides of the combustion chamber the mixture is burnt much faster overall (but still in a controlled way). One other advantage of a twin spark system is the elimination of ignition induced pinging. A weak spark (and/or slow burning mixture) in a big chamber (500cc and above) can lead to the effect, that the (pressure) shock wave of the ignition starts an uncontrolled, compression induced detonation somewhere else. You dont want that. You want the whole mixture being ignited by the flame front, not by pressure increase. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Advance
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