The capacitor in a points ignition

[CHICAGO]

Hi all

In a car old points ignition system, I understand the capacitor (condenser) main purpose is that of protecting the points from getting burnt.

The second purpose for this capacitor, could it be to make a resonant circuit among the ignition coil in order to prevent it from radiation?.

I mean the coil-condenser would make the system to oscillate at a lower frequency in the way that all the energy would be used to ignite the spark and there would be no loss in the case of a high frecuency radiation.

Am I wrong?

Another question. In what way does this capacitor help the primary coil to get those some 200 volts?

Thanks a lot in advance.

 

[Bob S]

When the points close, the capacitor is shorted and the coil primary charges up to about 2 amps (limited by coil internal resistance of ~6 ohms). When the points open, there is a very large V = L dI/dt voltage, ~300 volts, across the capacitor that resonates back and forth with current in the coil, for ~ 10 cycles. The coil secondary:primary turns ratio is ~100:1 so the coil secondary voltage is ~30,000 volts. See my LTSPICE simulation
https://www.physicsforums.com/attachment.php?attachmentid=20126&d=1250393723
The points close at 0 and 4 milliseconds, and they open at 2 and 6 milliseconds.
Bob S