Re: Condener Keeps burning up?
KaGee: I stated in my post if I was wrong I would apologize, here is my apology, I could not understand how a condensor filtered since it is on the cranking side of the circuit. See attached letter from Mr. Jim Lux, Senior Engineer with NASA.<br />"Well...<br />The capacitor does prevent arcing at the points. As the points start to open, the voltage across them starts to rise, if there's no capacitor, and you "draw" an arc (much like arc welding). The capacitor delays the start of that voltage rise a very short time, but long enough for the points to actually get separated far enough that a spark can't form.[interesting side note... voltages below about 300-400V cannot jump a gap, no matter how small, so the cap doesn't have to delay the voltage rise very long]. If there's no spark, there's much less erosion of the points. Actually, if the cap's not there, the arc dissipates the energy stored in the iron core of the ignition coil, and the sparkplugs won't fire...oddly, a failed ignition capacitor (condenser) almost made my father late for his wedding, and had that been the case, perhaps I wouldn't be answering your question now...<br /> <br />As far as RFI goes. If the capacitor wasn't there, you'll develop the spark, which will suddenly quench as the points get far enough apart. The sudden transient has significant RF energy, and since it's on the low voltage side, it's connected to all the 12V wiring in the car, so it has a good antenna (if not an actual wire leading into the radio through the power). The HV side (the sparkplugs) cause less interference because the wires are shorter, and there's resistance in the lead which slows down the speed of the voltage rise, reducing the RFI. In the case of the spark in the cylinder, it quits because the coil has run out of energy to put into it, so it has a "softer" falling edge, which makes less RFI.<br /> <br />To sum up... the cap reduces the RFI, but not by bypassing the RF to ground, but by making the ignition system work like it's supposed to."<br /><br /> <br />----- Original Message ----- <br />From: bennie cox <br />To:
jimlux@earthlink.net <br />Sent: Saturday, September 11, 2004 7:35 PM<br /><br /><br />Dear Mr. Lux:<br />I would greatly appreciate your opinion on the following subject.<br />I am in a debate with a gentleman concerning the condensor in a 1979 boating application.<br />He says the following "The capacitor buffers the spark on the points, keeping them from burning up prematurly as well as filtering the DC power line reducing ignition noise in radios and other marine electronics."<br />I say the condensor does nothing to suppress noise in radios and other marine electronics. In the 50 years I have worked on internal combustion engines, I have never read any thing stating that the condensor in a distributor, suppresses noise in a radio. Your opinion would be greatly appreciated.<br />Sincerely:<br />Bennie Cox <br />Mid Atlantic Marine<br />Yanceyville,NC<br /><br />Boatist: Your comments of 9-11 was not at all appreciated, and clearly written to degrade me. I went to a Junior college in 1968<br />and studies electronics. As I stated, my hobby is pinball machines, I am very familiar with filtering capacitors, all of the machines that use voice chips must have clean voltage or the sound will be distorted.<br />Since I am new to the forum rest assured with 50 years experience with internal combustion engines, 12 years in NASCAR racing and 35 years in all phases of the marine business,[repair, reconstruction, consulting, and brokerage] in the future I will extend the same courtesy you extended to me.<br />Regards<br />Bennie Cox <br />Mid Atlantic Marine
