- Wed Jul 11, 2012 1:29 pm
#14632
Just to clarify the advance and retard action of the Boyer/Pazon unit. Both makes of ignition unit work by DELAYING the spark from a fixed advance position...they do not actually advance the timing at all. The trigger unit is timed to fire the ignition unit at the full advance position but the ignition unit slowly and progressively delays the spark as the engine revs drop below the maximum. The rate of the delay in spark generation increases and becomes more rapid as the revs drop below about 2000rpm down to tickover. There is also more of a delay from about 500 revs to stationary which is very helpful in avoiding kick back. As the revs rise again the delay becomes shorter and gives the effect of advancing the ignition. Contrary to popular belief, the timing does not over advance the entire range of timing when fed with a low supply voltage. Irrespective of how low the supply voltage drops (as long as it remains in the operational range) the full advance figure does not change...ie: the complete ignition curve DOES NOT over advance. The only part of the timing that does change is that the delay becomes less at low revs (due to the lower voltage fed to the capacitor-resistor circuit that provides the delay) so the apparent effect when starting with a flattish battery is that the timing has become advanced but in actuality the timing is simply not as retarded as much as it should be. The rest of the advance curve from 500 rpm upwards remains on line as before. Hope this clears up any misunderstanding on the way the Boyer/Pazon works.