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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modern Fuel & Ignition Advance
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<blockquote data-quote="Pete Appleton" data-source="post: 94862" data-attributes="member: 145"><p>Grey one mentions a 'delay period' Comparing the published advance curves for the BTH and Pazon ignition systems it looks to me as though, in the lower part of the rev band, these are set to provide a 2.5 millisecond delay period before tdc.</p><p>I understand that this will not be a linear function as we take into account cylinder filling efficiencies etc but it is noticeable that Pazon reach maximum advance at only 2000 revs and do not advance any further.</p><p>BTH have a shallower curve and don't reach maximum until 3,000 rpm.</p><p>I wonder where these figures have come from. Is it a legacy figure taken from what could once be achieved with a mechanical ATD? Is there a good reason why we stop advancing at not much above mid revs?</p><p>I have always suspected that there could be more power available if we actually increased advance up to somewhere in excess of 45 degrees but don't achieve that until much higher revs.</p><p>Many years ago I attended a lecture by Cosworth racing engines. In a discussion afterwards with one of their designers he stated that increasing advance was providing corresponding power improvements right up until detonation point. Something along the lines of 'advance it up until it melts and then back it off a bit'</p><p>All of this is just my imagining and not backed by the slightest bit of science. has anyone got any dyno figures?</p><p>[ATTACH=full]21983[/ATTACH]</p></blockquote><p></p>
[QUOTE="Pete Appleton, post: 94862, member: 145"] Grey one mentions a 'delay period' Comparing the published advance curves for the BTH and Pazon ignition systems it looks to me as though, in the lower part of the rev band, these are set to provide a 2.5 millisecond delay period before tdc. I understand that this will not be a linear function as we take into account cylinder filling efficiencies etc but it is noticeable that Pazon reach maximum advance at only 2000 revs and do not advance any further. BTH have a shallower curve and don't reach maximum until 3,000 rpm. I wonder where these figures have come from. Is it a legacy figure taken from what could once be achieved with a mechanical ATD? Is there a good reason why we stop advancing at not much above mid revs? I have always suspected that there could be more power available if we actually increased advance up to somewhere in excess of 45 degrees but don't achieve that until much higher revs. Many years ago I attended a lecture by Cosworth racing engines. In a discussion afterwards with one of their designers he stated that increasing advance was providing corresponding power improvements right up until detonation point. Something along the lines of 'advance it up until it melts and then back it off a bit' All of this is just my imagining and not backed by the slightest bit of science. has anyone got any dyno figures? [ATTACH=full]21983[/ATTACH] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modern Fuel & Ignition Advance
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