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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Timing & modern Fuel
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<blockquote data-quote="Magnetoman" data-source="post: 47279" data-attributes="member: 2806"><p>The chart in the previous post looks very suspiciously like the output from someone's ruler and pen, not actual measured data from a piece of electronics. As such it almost certainly is only an approximation of any given unit's actual response. Because individual electronic components have tolerances (e.g. +/-5%), there also will be unit-to-unit variations in the output. Whether those variations are larger than the width of the line drawn on the above graph could only be known by measuring several units, but I suspect they are. </p><p></p><p>The optimum advance curve for a specific motorcycle would depend on factors like its compression ratio, inlet port shape, and cam profile. While those factors could be dealt with, the variable properties of the fuel blend available in any given region of a country at any given time of the year (and it being different next year than it was last year...) make getting too deep into this fairly hopeless. However, if someone were concerned with having the optimum advance curve for their own motorcycle for a racing fuel whose properties they could count on as not changing, they would have to do dynamometer runs by varying the amount of advance at, say, 250 rpm intervals, then have a unit fabricated to reproduce the optimum results found. </p><p></p><p> It's only one small step from the above to installing fuel injection on a Vincent, which then would allow the advance curve to be altered at will as the fuel blends change. Kits actually exist to allow fuel injection to be added to any engine desired. A friend is currently reviving a damaged modern Ducati by doing that rather than buying the very expensive OEM components, but machining a simple pair of throttle bodies would let this be done just as easily (or with just as much difficulty...) on a Vincent.</p></blockquote><p></p>
[QUOTE="Magnetoman, post: 47279, member: 2806"] The chart in the previous post looks very suspiciously like the output from someone's ruler and pen, not actual measured data from a piece of electronics. As such it almost certainly is only an approximation of any given unit's actual response. Because individual electronic components have tolerances (e.g. +/-5%), there also will be unit-to-unit variations in the output. Whether those variations are larger than the width of the line drawn on the above graph could only be known by measuring several units, but I suspect they are. The optimum advance curve for a specific motorcycle would depend on factors like its compression ratio, inlet port shape, and cam profile. While those factors could be dealt with, the variable properties of the fuel blend available in any given region of a country at any given time of the year (and it being different next year than it was last year...) make getting too deep into this fairly hopeless. However, if someone were concerned with having the optimum advance curve for their own motorcycle for a racing fuel whose properties they could count on as not changing, they would have to do dynamometer runs by varying the amount of advance at, say, 250 rpm intervals, then have a unit fabricated to reproduce the optimum results found. It's only one small step from the above to installing fuel injection on a Vincent, which then would allow the advance curve to be altered at will as the fuel blends change. Kits actually exist to allow fuel injection to be added to any engine desired. A friend is currently reviving a damaged modern Ducati by doing that rather than buying the very expensive OEM components, but machining a simple pair of throttle bodies would let this be done just as easily (or with just as much difficulty...) on a Vincent. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Ignition Timing & modern Fuel
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