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Post by baumanjohn on Jun 19, 2011 16:25:43 GMT -5
Still in the learning curve on this stuff.So,can someone tell the purpose of it??
I know there is a AC and DC CDI
thanks John
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Post by tour96se on Jun 19, 2011 17:39:23 GMT -5
it's basically your ignition "brains"
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Post by sprocket on Jun 19, 2011 18:36:15 GMT -5
Basically it takes an AC voltage from the stator (alternator) and feeds it to a capacitor in the CDI... this boosts the voltage to about 400 volts A signal comes from the stator when the flywheel is in a particular position and the CDI releases the capacitor charge to the ignition coil and it jacks up the voltage to 15,000+ volts and send it to the spark plug.. that sparks... Then this is repeated... at idle about 1500 times a minute 8,000 times at full throttle Attachments:
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Post by sinister357 on Jun 19, 2011 19:58:49 GMT -5
it's basically your ignition "brains" yeah. from what i've read on scrappy's ads, ignition curves are programmed in there. |
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Post by sprocket on Jun 19, 2011 20:09:46 GMT -5
>>ignition curves are programmed in there.
There is nothing programmed in there...
It is just a small circuit board and a capacitor and a couple of feed back circuits for rev limitation and a transistor etc.
Don't believe the marketing B.S. these CDIs are not programmable
Cut one open sometime and have a look...
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Post by sinister357 on Jun 19, 2011 20:41:16 GMT -5
>>ignition curves are programmed in there. There is nothing programmed in there... It is just a small circuit board and a capacitor and a couple of feed back circuits for rev limitation and a transistor etc. Don't believe the marketing B.S. these CDIs are not programmable Cut one open sometime and have a look... what are the advantages of electronic CDI then? or purpose. rev limiter not a program? |
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Post by D-cat on Jun 19, 2011 22:12:21 GMT -5
Electronic CDIs do have settings but they're not really programs. Some do in fact have electronic ICs and others are just simple build and fire trigger circuits with a frequency dependent delay circuit (the more frequent the trigger, the less the delay, hence the advance curve); the trigger is 13 o advance TDC if my memory serves correct. A simple rev limiter isn't hard to incorporate into the design, just run a timer/oscillator against the trigger signal on a gate to ground and when the frequencies match the gate opens, the firing circuit never gets a signal. IC types have the ability to advance further depending on the "program" and to back down or level off the advance at higher rev which a simple delay circuit can't do. The adjustable IC CDIs have the ability to select the curve and the rev limit you want so you can literally dial in what works best for your bike. Too bad most don't have any instructions. The AC CDI requires a rectifier and voltage regulator which the DC doesn't, but until recently a DC CDI required an additional inverter circuit which was part of why it was larger; newer ones have more things integrated into ICs so now it's no longer so easy to tell an AC from a DC CDI just by looking at the size (yep, the new DCs have shrunk) so check marking for clues and hope it outright tells you.  --- I know this is beyond the scope of the question but if interested in actual programmability, check out the threads on EFI kit installation. If using the ECU controlled CDI that comes with the kit, you are able to actually program the timing curve. |
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