jj@rabbit.UUCP (06/03/83)
Well, I should know better than to get into a debate in net.auto, where superstition runs rampant, but alice!wookie was right about the ballast resistor. The gentleman who recently pointed out that the ballast resistor is switched out during starting is also right, but only with some cars, and some years. While all cars (except some of those with electronic and/or capacitive discharge ignitions) have ballast resistors, all cars do NOT switch out the ballast resistor during starting. While examples no longer occur to me, since I've had no standard ignition systems in the last 6 years, several of the cars I've owned, including an early model Datsun B-210 <ecch, for other reasons>, did not switch out the ballast resistor at any time. While the engine is not turning, the ballast resistor is indeed essential to prevent the coil from drawing an enormous amount of current. (Unless, of course, you have one of the GM cars with the ballast resistor built in to the coil. <Cars with this type of coil, by the way, do not switch out the ballast resistor, except in the earlier versions with 3 primary terminals. The reason should be obvious.>) While the engine is running,the ballast resisitor still limits the current through the coil at low RPM's, much more than it limits the current at high RPM's. Why? Because the longer the points are closed, the more current flows through the coil. <This is, in fact, the standard defination of inductance, an attribute commonly associated with coils of all sorts.> At low RPM's, the points are closed longer, the peak current is greater, the ballast resistor heats up more, and as a result, since it is deliberately constructed of a type of wire, usually nichrome, which has much higher resistance when hot, limits the coil current. At high RPM's, conversely, the peak current is less, the ballast resistor cools down, its resistance lowers, and the coil then charges (yes, increasing the current in an inductor is "charging" it)) more than it would have without the ballast resistor. Since the peak current through the coil and the spark voltage are proportional, the ballast resistor helps (and does a reasonably good job) keep the spark voltage constant. have a nearly acceptable day, all rabbit!<don't mail me>jj
jeff@tesla.UUCP (06/08/83)
The Chrysler Omni/Horizon (1.7L VW engine) certainly doesn't switch out eh the ballast resistor while starting, as I learned by experience. Does anybody know about the 2.2L? JF