Take an hour and
skim through this, absorbing the pertinent parts as required. It appears to have been written prior to WW II, but is pertinent to understanding "Sparking Voltage" ie, the requirements for Ignition system capability to fire the spark plug.
What I just re-learned:
As cylinder pressure increases voltage required at the plug increases.
A gap in free air (distributor cap) requires less sparking voltage (1.5 KV) than one inside a chamber (6,000KV).
The secondary voltage of the coil will only rise to the sparking voltage, then fire, even if it is capable of rising much further.
When spark occurs, the air within the 'gap' is ionized, ie electrically charged so it conducts electricity. If the gap is very short, not enough area is present to ionize enough particles to cause the required full ignition event.
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Some conclusions on my part:
"Blowing out the spark" is idiotic mumbo-jumbo. No such thing occurs. Either there is sufficient voltage to jump the gap, or there isn't. Today's reading revealed that "turbulence" plays an insignificant role in Sparking Voltage in automotive applications.
Guys that run close gaps (less than .035) and actually see an improvement (I posit that most people don't see an improvement, and are just closing up the gaps because it "makes sense" [it doesn't] and it's monkey-see, so I'll do-it-too.) have a basic ignition system problem. As cyl pressure increases, so does the voltage required to fire the plug. Once the system is incapable of producing this voltage, spark does not occur.
The higher sparking voltage required by boosted engines
operating under boost will also be present at the gap in the rotor/cap. This
may result in slightly increased deterioration of the rotor/cap contacts over time.
Multiple discharge spark systems (MSD) will cause the air within the cap to ionize at high RPM (frequency) and voltage (high cyl pressure from boost/throttle) to the point that the spark is conducted to all plugs at once. This is not a new phenomenon. I recall reading about racers in the 60's having to drill vent holes in their caps to prevent this ionization when using early MSD systems.
The wider the plug gap, the more power the engine will produce. Bill Jenkins discovered this in the mid-70's, and writes about it in his book "The Chevrolet Racing Engine". They ran gaps in the .050-.060 range, the limitation being able to start the engine. (Today's reading revealed that
temperature has a big effect on sparking voltage, hence why Grumpy's maximum gap was limited by ability to jump the gap on a cold plug).
Last conclusion: Only 1-2 peeps will bother to read the link I provided, or this post, and attempt to understand the points I've made or outlined, whether I'm correct or not. I researched, and wrote this post
because I re-learned quite a bit about what I remember about ignition systems, and learned some new stuff as well myself. (That temperature influences sparking voltage, air-gap voltage being substantially less than combustion chamber voltage, and system capability is irrelevant to the voltage at the gap).
I would like to think that others learned something from my efforts as well, but I doubt anyone other than Don bothered to read this far. If you did read this far, and even better learned something, great. And thank you.
I'm currently running methanol, under impression with an upgraded ignition system fuel will burn smoothly, let alone show overall performance. At this point I have had 2 msd dis fail and I returned to stock dis thinking its an bad patch and try later. What's people views with an 6al I believe? I'm tempted with the plug and go harness, if it burns out I believe I can return to stock dis. Sorry guys, what's your views on box with stock ignition? I do have an msd coil, not installed, dam it look good installed.
