In response to:
> The consenser/s (capacitor/s) is/are chosen to RESTORE the phase
>relationship of current and voltage, using CAPACITIVE REACTANCE, (Xc The
>capacitive reactance (ac resistance) a capacitor offers to alternating
>current or pulsating direct current.
>The equation: 1over 2pi fC......where f is in hertz and C is in farads.
>
> Inductive reactance and capacitive reactance are INVERSELY PROPORTIONAL
>to eachother: THEY CANCEL EACHOTHER OUT...and that is the goal.
Jim,
I agree with your assessment of the situation, However, you did not point
out the shortcomings of even this situation. That being that the
cancellation point of reactances, better known as resonance, only occurs at
one frequency (i.e. one rpm) which was selected for the mid frequency usage,
and the "optimum" configuration degrades slightly at all other rpms. Too bad
we live in a world of "best that we can do situations". This is not intended
as a critique, just additional info. I believe that this is one of the
factors that was being addressed with the introduction of the capacitor
discharge ignitions. In this design the "charged" capacitor (which has a
much larger value than the capacitor across the points and is charged to
around 400Volts DC) was discharged through the coil primary giving a more
ideal initial single pulse of energy. I believe that the coil used with
these units also had a much lower primary inductance which aided in the
"transformer" action as opposed to a collapsing field kick-back transformer.
The CD ignition essentially removed all of the demand that was placed on the
burning durability of the points by going to a solid state switching device.
It is interesting to look at the size of the multiple coils being used on
the new engines. Technology has definitely made things better in regard to
the ignition system. I can recall getting maybe 12,000 miles, at best, on a
set of plugs and points back in the 60's. Now, I might check the plugs at
60,000 if I have nothing else to do.
Cullen Bennett
Tempe, Arizona USA
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