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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
BTH magnetos
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<blockquote data-quote="peterg" data-source="post: 12178" data-attributes="member: 446"><p>Howdy sir,</p><p> </p><p>Starting? Doubt it's better than a distributor either - all previous comparisons made to the Lucas mag - and in fact, within those space confines for the generating portion of the instrument itself, you could likely exceed that BTH's low rpm output with a 6V Bosch "blue" coil on a decent battery but that's straying from the beaty of this unit. A compact reliable ignition source, with accurate timing adjustment and without need for a charging system.</p><p> </p><p>Regarding crisp acceleration with your former distributor...if I may digress ad naus-ee-um for a moment here. That was all about the advance side of its operation and it likely was feeding alot more (maybe too much) initial advance in at low rpm than what you have now from the BTH whose mapping is likely more linear (analog so not programmable) as it relates to rpm gain. Example: an old centrifugal advance in a U.S. Porsche 930 (with the vacuum retard disconnected) had about 6-7 degrees steady advance on throttle tip in - and it felt sluggish - with essentially a flat sweep to max. My 930 <a href="http://www.patwilliamsracing.com/efipkgmotor.htm" target="_blank">here</a> converted to EFI with completely programmed/integreted ignition timing has 7 degrees at idle. Using manifold pressure sensing in its map, on throttle tip in it can jump immediately to 20 if not 34 degrees without any rpm gain. As the efficiency of the motor as an air pump improves with rpm gain, ie, the cams, port velocity, etc. begin working etc. and the all important cylinder pressure rises, the high initial advance is wither taken out of it or ceases to rise at a rate comparable to that rpm gain. The net result is the same vehicle equiped in the latter format feels delightfully responsive and 500lbs lighter than the former in the lower rpm ranges.</p></blockquote><p></p>
[QUOTE="peterg, post: 12178, member: 446"] Howdy sir, Starting? Doubt it's better than a distributor either - all previous comparisons made to the Lucas mag - and in fact, within those space confines for the generating portion of the instrument itself, you could likely exceed that BTH's low rpm output with a 6V Bosch "blue" coil on a decent battery but that's straying from the beaty of this unit. A compact reliable ignition source, with accurate timing adjustment and without need for a charging system. Regarding crisp acceleration with your former distributor...if I may digress ad naus-ee-um for a moment here. That was all about the advance side of its operation and it likely was feeding alot more (maybe too much) initial advance in at low rpm than what you have now from the BTH whose mapping is likely more linear (analog so not programmable) as it relates to rpm gain. Example: an old centrifugal advance in a U.S. Porsche 930 (with the vacuum retard disconnected) had about 6-7 degrees steady advance on throttle tip in - and it felt sluggish - with essentially a flat sweep to max. My 930 [URL="http://www.patwilliamsracing.com/efipkgmotor.htm"]here[/URL] converted to EFI with completely programmed/integreted ignition timing has 7 degrees at idle. Using manifold pressure sensing in its map, on throttle tip in it can jump immediately to 20 if not 34 degrees without any rpm gain. As the efficiency of the motor as an air pump improves with rpm gain, ie, the cams, port velocity, etc. begin working etc. and the all important cylinder pressure rises, the high initial advance is wither taken out of it or ceases to rise at a rate comparable to that rpm gain. The net result is the same vehicle equiped in the latter format feels delightfully responsive and 500lbs lighter than the former in the lower rpm ranges. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
BTH magnetos
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