In all reality, I don't think there is going to be a whole lot of difference in cylinder pressures by changing altitude...... at least, not a significant enough difference for the spark plugs to notice...

That said, a higher energy ignition system isn't going to HURT anything.

 

Thank you. The whole point behind the new coil anyways is its time. The pin has some gouges from age. And it's rusting so wether it helps or not almost doesn't matter. I just need something updated. And the MSD blaster coil is cheaper and so far buying the demon coil is pointless because I'm not building it up enough for that hot of a spark

 

Kinda sorta but not really. Paschel's Law says we'll require less voltage to initiate and sustain the arc, but that's just the spark plug part of it. We also have the rest of the reaction to think about, and at lower atmospheric pressure we have lower (fuel/air) charge density combined with lower fuel volatility making it harder to actually achieve the desired reaction. Opening up the gap makes for a longer arc channel, exposing its energy to a greater number of hydrocarbon molecules, and so more reliably firing the fuel/air charge. It also reduces the variability in flame front propagation.

We run lower octane fuels here in order to compensate for the lower fuel volatility at elevation -- you can't even get 93 octane fuel here because only a highly modified engine could run acceptably well on it. The lower octane is only part of the picture, though. In the dark and distant past it took more effort to get decent engine performance up here, usually re-jetting the carb, advancing ignition timing by ~30 degrees or more on a typical V-8, running spark plugs a heat range hotter than stock, and opening their gaps four to six thousandths, too. The most important things were dropping the octane and advancing the ignition, which between them ensured that the flame front had time to build and start the rapid pressure increase at the right point in the piston travel. These days we don't twiddle timing or mixture manually, but that wider spark plug gap is still useful to prevent (fuel charge) ignition failure at low RPM when there's relatively little flammable stuff in the hole and less turbulence to ensure a consistent mix.

It's not something you'll often notice down here where I live on the side of the mountain at 6300', but on the higher passes you can stand on the shoulder of the road below the summit and hear intermittent ignition failures in many of the cars that pass.

 

Makes sense. Thanks for the discussion. The double whammy...less dense/reactive air that is less likely to be turbulent.

 

You're welcome. Ignition systems are fun to fool with even if there is no telling (yet) what's really happening at the subatomic level to make spark plugs work the way they do. The magic is cool just the same.