I suspect that you really mean RA8HCs on the champions. 6R12 is the HD number (tho it's made by champion) I run the RA6HCs (cooler) but don't have the ion sensing. The 8s should work fine. Will need to regap tho.

 

 

Interestingly enough the OP hasn't returned to update their test results, all of the conversation here has been either thread hijacks or corrections.

 

well the truth is that any spark plug regardless of type suffer from the same abnormalities. each design has +/-'s and each helps solve one piece of a puzzle but none solve everything and some are just pure crapola.
that said, who said iridium plugs cannot be used with ion sense? truth told, they are stock plugs in a lot of vehicles. true, there are diff types of ion sense systems.
the plug gap plays an important role and the suggested gap or gap out the box is to be taken with a grain of salt. for gins and giggles, too big can lead to misfire and too narrow can stifle spark kernel.
the truth told, no matter the plug, if it is properly set has NADA to do with the ion sense. the plug only provides a bias voltage for the sense system and initiate ignition. once the plug goes out, it is then the sense system comes into play as it reads combustion and not spark plug since it is basically dead out of the water, it is the ionized gases that are read for electrical conductivity.
plug wear is a factor and iridium plugs excel here and is used in mulit-strike ion sense systems.
about two months back, i removed the plugs from my nissan, yep iridium and replaced with iridium but not the stock plug, vehicle would not run right, increased gap .004 and runs like a scalded ape.

 

What you say increasing plug gap helps makes sense. I'm not sure if plug provides a bias voltage or simply creates a discharge path for the capacitor that gets charged during spark. I suspect it's more of a simple resistance measurement across the plug.. Looking at the dephi document, the third scope display skewed in that you really don't know where ground is as the they changed the scale and sweep. Either way if increasing the gap seem to help, it's worth a try. I like the idea off opening the gap on TCs since it can create a better burn for closed loop systems. Late mode HD ignition systems really have enough power to generate a good spark but iridium plugs spark at lower voltages even with slightly larger gaps.

 

 

I have been using NGK Harley replacement plugs, trouble free, since my doors opened.

Bob,
Amazing what can be done with plug gap and why the adage of more is better doesn't fit here either.

 

I think you'll find that increasing or decreasing the gap to correct things really depends on the situation. Going to a tighter gap slows the start of the flame kernel. I've seen help with warm starter kickback. It's a sign that there may be too much timing.. Alternately widening the gap can assist in kernel spread or it possibly effects what the ion sensing circuitry does in the case of iridium plugs. Plug heat range can also have an effect. While some of this could be determined experimentally on a dyno, it has not been done.. In the mean time those that don't have the resources continue to experiment.

 

No way I can buy post 18. Do you know how fast electricity moves?
And hot kick back on starter on a modern FI Harley depends on the luck of where the pistons stop in cylinder and the charge left in intake and cylinder from injectors.
Combine that and a half worn out battery and or loose connection at battery causes that annoying starter bang. Kickback puffs the intake. Most of the times, it bangs the starter and compensator when it pops on the exhaust side since that pops the engine over like a shot charge in large industrial engines that have no electrial starter.

 

Electricity flows at the speed of light in a vacuum. It slows a bit when there is a dielectric involved (IIRC it's speed of light/square-root of Er).

Not sure what you point is by example. It is valid but so is closing the gap or cooler heat range on hot starts when running a high compression motor that has everything else up to snuff. Especially without compression releases..