Re: Pertronix Ignitor vs Ignitor II
Changing the dwell changes the spark timing, what's the difference between that and an electronic advance curve?
Not necessarily. The module on the Thunderbolt IV advances the timing anything up to 24 degrees (for the V8, 14 for the V6). and that's not done by changing the charge time on the coil. It's done by 'seeing' the crank position (from the reluctor in the distributor) and determining the RPM (by measuring the time between the pulses from the reluctor) and firing the coil at the appropiate time, determined by the programming of the module. It actually creates a delay (of spark firing) at speeds lower than when maximum advance occurs (usually 3000RPM). <br /><br />Some figures...<br /><br />dwell angle of points on V8. 30 degrees. this means that the points are closed for 1/3 of the time between firings of the coil. At WOT of, say 4500 RPM that would be 1.11 milliseconds (1 millisecond is 1/1000 of a second) charging time for the coil for each spark.
BUT 2.22 mS would be lost while the points were open. This is done to enable the points to open quickly enough to achieve a (relatively) clean break between open and closed, thus reducing the burning of the points and to create a fast enough transition to produce a good quality spark. If you were running electronic ignition with variable dwell, it could change that charging time to, say 3 mS (total time between firings at this engine speed is 3.33 mS) and, because electronics can switch between on and off so fast, it would improve spark quality and reliabilty. The actual timing of the spark would still be determined by the advance curve, programmed into the module. It has to be done this way because the engine's timing curve is not always linear against engine RPM, whereas dwell changes are.<br /><br />Chris.............
<br /><br />Chris..........<br /><br />Edit: Aldo, you were typing at the same time as me. Sorry. Also what you are talking about is an electronic advance curve, not variable dwell.
