I read in the forum posts about ignition coils as they are posted. The dominant opinion about them seems to be: 'hotter is better'. This is certainly appealing and, as I understand it, true after a fact. A hotter coil should make for a more intense spark across the gap in the combustion chamber. If a manufacturer claims a coil develops 40,000 volts, the fuel/air mixture shouldn't stand a chance.
In one of my careers, I was a trainer for an engine manufacturer, (Outboard Marine Corporation: defunct since 2000) I learned ignition systems operated a little differently. The voltage needed to ionize the combustion chamber and push current across the spark plug gap only required 8,000 to 12,000 volts depending upon pressure and fuel/air load. Without regard to a coil's ability, once the threshold has been reached, the electrical path that makes up the secondary circuit, past the plug gap to ground is going to be made. If it only takes 8,500 volts to jump the gap, then 8,500 volts is all the coil will make. Sharp edges on the plug electrode are good for directing the spark across the gap, oil and carbon soot is bad, etc.
The advantage gained from a Crane or Pertronix kit comes from the increased, reliable time current can flow through the primary without overheating the coil. I don't see anywhere in Crane's documentation that multiple sparks are generated by their system, so I maybe current flows longer across the gap through the RPM range. If we watch the spark cross a gap, I believe our interpretation of a bluer or hotter spark is the result of duration as the potential across the secondary is depleted over a longer time (we see it a split second longer).
I don't find any information from any manufacturer explaining how canister ignition coils develop more potential with the same design used since ... a long time ago. The voltage limit across the primary is the same. Once the coil is saturated with current, the voltage potential doesn't change. The coils themselves are still in an oil bath with the secondary wrapped around the primary which in turn is wrapped around an iron core (I think they're steel plates actually). I'm not claiming that Mallory is selling snake oil. Just that I don't know, and would gladly learn differently if I'm wrong.
Does my understanding of ignition coils make sense? If it does, should the only issue with ignition coils be that they break down over time? An OEM coil is just as good as a Crane PS40 when new is compared to new? I ask because there is a lot of experience within this forum.
My question to those who use a Pertronix or Crane kits has to do with spark plugs. If dwell is constant and reliable, electronic ignitions can push the coil to a higher potential across the RPM band. Do you gap your plugs at .045", or .040" instead of .035"? As I recall, a hotter spark plug means more insulator is exposed to the combustion chamber and/or maybe the plug extends a bit further into the combustion chamber. Which plug do you prefer for use as a hotter plug?
