Brian Evans wrote:
> Early cars used internal resistor coils. Later cars went to external
> resistor coils.
Well, not quite true. Early cars used coils with a different
turns ratio. When the ballast concept was developed/stolen, the
turns ratio was changed in the coil to make it work. It's not
really an "internal resistor".
> Both types give about 9 volts to the coil under normal operating
> conditions.
Again, not quite true. The non-ballasted coil is wired to run
properly with the full 12-14V applied to it. The ballasted coil
has a different turns ratio to provide equivalent spark with
only 6-9V on it when running.
> Exceptions - Many later cars have an extra terminal on the solenoid so that
> the resistor is bypassed during starting
This is actually "the point" of a ballasted system. By taking
down the running voltage, you can get the same behaviour during
running and get a "free giant spark" at starting by running the
original equipment at a much higher primary current.
> giving higher voltage to the coil while the starter motor is drawing
> down the voltage.
Again, I don't really think the goal is to deliver the same
spark, although the start motor sure hurts. The goal is to
deliver a larger spark when starting so the car catches quicker,
and the same spark while running so that you don't burn points
out with the large sparks.
--
Trevor Boicey
Ottawa, Canada
tboicey@brit.ca
http://www.brit.ca/~tboicey/
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