Teach me about ohms and coils Options

[jsayre914]

I am currently running a stock distributor on my 2.0 w/ Djet. It has the pertronix ignitor module made for my distributor with the vacume advance. I also had a flame thrower 3ohm coil made by pertronix. I am not sure how many ohms a stock bosch coil is, but my question is...

most high performance coils such as mallory, crane, even the flamethrower (not the one I have) comes with a resistance of .06 or less. Why is this, and what does the ohms do for you anyway. I am thinking to put one of the VERY low ohm coils on my engine to see if any better performance.

If you dont mind also explaining why i threw out my ballast resistor when I originally put the pertronix in. (as per installation instructions) what the heck did that do for a stock coil thats not needed for a 3 ohm coil?



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[ArtechnikA]

_Very_ short version:

Stock Kettering ignition uses a coil. It's a nice 19-century way of turning battery voltage into the BIG voltage needed to jump a spark gap at cylinder pressure. It's an energy storage device. During the 'dwell' time, it charges. When the points open, it discharges acting like a transformer.

Capacitive-Discharge ignitions do not use coils, although the pulse transformers they use frequently look like coils of olde, and people often call them that. But they're pulse transformers.

With points and a Kettering ignition, ALL the ignition power runs through the points. You use a ballast resistor to keep the points from burning up with to much current.

Coils have fairly high primary resistance because they need a lot of turns on the transformer to turn 12V into 20,000V. A CDI starts at 400-ish V and doesn't need as much help from the transformer part. Plus, since it's not used to actually store energy (the capacitor in the CDI box does that) it doesn't need to build up as big a magnetic field.

with a CDI, the points aren't carrying all the ignition power, they simply switch the CDI electronics.

I have nothing more to say about pertronix (beyond my opinions that are still in several threads here) other than to speculate it would be wise to use whatever they recommend, lest you loose the Magick Smoke.

In general, I prefer to stick with whatever the spark box maker recommends - I use a Crane pulse transformer with my Crane HI-6, and I used MSD High-Vibration "coils" when I ran an MSD.