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Re: Re: spark plug gap after electronoc ignition
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Posted by IHank on January 03, 2001 at 23:23:20 from (207.177.47.170):
In Reply to: Re: spark plug gap after electronoc ignition posted by Ken T on January 03, 2001 at 18:49:53:
Ken T has all good comments. I'll add a bit from where he left off... Electronic ignition systems use transistor switching, that allows coil primary current numbers well above what the old contact points would handle. The old coil can, and often is, used with retro-fit electronic conversions, especially the low bucks options. Those customers get freedom from fiddling with contact points, but the firing power and capabilities of the OE system remain the same. If the conversion kit included a new coil it is a completely different situation. e.g., The GM HEI system introduced in 1974 gave a huge leap in ignition power, by doing an integrated design job with the electronic module and the coil. It was one of those things that would fire a rusty nail in a bucket of water, or destroy your manhood while pulling plug wires to check RPM drop on a running engine... Yeah, some of you know what I'm talking about here! Back to the original question... With increased coil voltage and current output potential, which electronic systems make possible, one can go either way- increase the gap, or increase the spark firing time. During the 70's & into the 80's GM increased the plug gap, out to 0.080" last I knew of. That gave a physically longer spark and increased exposure to the swirling fuel/air charge to be ignited. A counter-culture in the repair industry saw opportunity and went the other way. They stood fast with the decades proven 0.032" spark plug gap. By doing so they got a longer spark burn time. The spark lasted longer, increasing the odds that it would initiate mixture ignition. All this was, and still is, seeable and dooable by people that have an ignition scope and know how to interpret the squigles on the screen. An inverted screen pattern means the coil primary connections need to be reversed. A common problem with 6 - 12 conversions... A real high firing spike means the high voltage is having a hard time firing the plug. A moderately high firing spike often told that wide gap plugs were out there. High stress on the secndary system parts. The high spike usually was followed by a short firing line, indicating the time the plug actually made a spark. Plugs gapped in the old fashioned 0.025" - 0.032" range gave relatively low firing spikes on the left side of the screen. Low stress on insulation in the secondary system parts. Those usually had a relatively longer firing line, meaning that the spark lasted longer in terms of milliseconds. The system designer's had to argue about long physical spark vs. long time burning spark. The beauty was that the new technology gave designers tremendous firing power for theory and publicity fiddling around. It also allowed the counter-culture auto service tecchies to make money and make happy customers with the old tried and proven plug gaps. A short bottom line on this long winded reply- "Hot coil" or OE coil, either way stay with the OEM plug gap for your engine. IHank
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