11-03-2011, 12:43 PM | #16 |
Join Date: Mar 2009
Location: Southeastern Washington desert
Posts: 14,761
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What would be the advantage of a programmable CDI? Why do they fail so often? I assume you have to replace one of the tiny electronic gizmos? how the heck do you know which one?
I have been SOUNDLY outgeeked here. :wink:
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11-03-2011, 02:19 PM | #17 |
Join Date: Mar 2009
Location: Sardis, BC, Canada
Posts: 25,977
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That's just basic four stroke care and feeding. As RPM increases, the point in time where the spark occurs (measured in crankshaft degrees) needs to advance. IOW, as the engine spins faster, the spark needs to light sooner, so that complete combustion can occur. It's a delicate dance, because if you start the spark too soon, complete combustion will try to drive the piston down while its still on the way up. We all know the sound of detonation; it's much like rocks in a coffee can.
A programmable CDI allows you to tailor the spark curve to meet the needs of a specific engine. BTW, your XR250R likely has a mechanical advance system that works with the CDI, because that's how they did it back in the day. As RPM increases, weights swing out when enough centrifugal force is applied to overcome the spring tension. Timing is then advanced to match the needs of the engine. I played with the weights and springs in a GM HEI distributor once, and I got remarkable results. Not only was there a seat of the pants increase, the fuel economy jumped by about 40% (the car was regularly driven very hard by a buddy of mine).
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11-03-2011, 03:28 PM | #18 |
Join Date: May 2007
Location: Altamont, Kansas
Posts: 15,103
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He went from 5 to 7 mpg. :wink:
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11-03-2011, 09:01 PM | #19 | |
Join Date: Oct 2009
Location: Alberta, Canada
Posts: 3,274
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Quote:
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11-03-2011, 10:24 PM | #20 | ||
Join Date: Jul 2008
Location: Idaho
Posts: 25,054
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Quote:
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Spud
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Spud "Never argue with an idiot. He will drag you down to his level, and beat you with experience." Mark Twain 2015 Zongshen ZS250GY-3 (RX3) 2006 Zongshen ZS200GY-2 (Sierra 200) 2005 Honda XR650L 2004 Honda CRF250X 1998 Kawasaki KDX220 Mods made to my Zongshen ZS200GY-2: http://www.chinariders.net/showthread.php?t=6894 |
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