Iridium Plugs Again

[koko64]

Had some good results recently running Iridium spark plugs with a big 1- 1.1mm gap. Just to clarify, more torque and throttle response, making the motor pull hard from low revs. Figured my Exactfit coils, Ignitech ignition, NGK race wires, solid charging system, upgraded wires/ground leads would handle the extra load. Im also running a Shorai LFX18 battery. While such big gaps exploit the strengths of iridium plugs are there any particular issues I should be wary of with the extra demand on the charging system?
I ask because my nearly new Electrosport regulator died today (service restored with a manky old oem Ducati Energia regulator). The Shorai is on save mode with an Optimate charger and hopefully defibs ok. I fitted a spare Shorai LFX14 and the old energia reg works a treat. Wiring good, alternator good and battery getting 14-14.5V with the old oem reg.
Coincidence or related to my cavalier spark plug gaps?  Possible in your experience?

[ducpainter]

I don't think the plugs have anything to do with it.

The coil is responsible for the spark and the coil uses what it uses, regardless of plug type.

Simple coincidence.

[koko64]

Thanks. I wanted to be sure there was no left field anomaly that would void the 12 month warranty. The reg is 8 months old . I hope it hasn't killed the battery, because sure has killed my right knee pushing the bike up a country hill.

[koko64]

Warranty claim submitted.

The large plug gaps may have assisted more complete combustion since the plug colours lightened up a little (same jetting, same test roads and same hi octane fuel supply). These iridium plugs come with a 0.9mm gap (NGK DPR8EIX-9) which is probably fine, but I wanted to test the theory about larger flame kernals via plug chop and response/acceleration tests.
I normally run regular DPR8EA-9 plugs which also have the 0.9mm gap, so it seemed like there was little to gain from using iridium plugs unless exploiting the strength of their ability to fire large gaps and the benefit to large combustion chambers. I ventured to 1mm then, 1.1mm thinking that was about as far as should I go. I forgot to use my spark gap tester which would have shown me the limit. Next time.

It's no use doing this unless the ignition system is strong enough to support it and I doubt the capacity of the old carbed coils to do so. There are also threads here which report bikes running worse when using iridium plugs with small gaps as Howie has explained.

Anyway I tried large gap iridium plugs and they seemed beneficial under those conditions, otherwise you might be wasting your money if you are expecting a significant performance increase.

[ducpainter]

We did the same thing back in the 70's with 2 strokes and car coils. Back then it was Gold Palladium plugs. Stopped plug fouling.

[Howie]

You got the tech.  Spark kernel. sufficient gap and coils good enough 

[koko64]

You got the tech.  Spark kernel. sufficient gap and coils good enough  

We did the same thing back in the 70's with 2 strokes and car coils. Back then it was Gold Palladium plugs. Stopped plug fouling.

I didn't know you played with that black magic.

I settled on 1mm gaps with the Iridium plugs which ran the same spark colors as 1.1mm. If I was running hand grenade sized Dyna coils I would try 1.1mm gaps over the long term. My fuel economy has improved with these large gapped Iridiums to the tune of edit: pardon me fellas. 15 km per litre or about 270 km per 18 litre tank (early model tank) . Not bad.

[ducpainter]

IIRC, we used some pretty extreme gaps. I don't remember the numbers exactly, but I think it was much larger.

Of course, the coils we were using were capable of running 8 cylinders and we only tasked them with 1.

[Howie]

Remember back when cars where running so lean back in the '70s?  Some cars were running systems capable of up to 40K volts and spark plug gaps as wide as 1.5mm (.060")?

[ducpainter]

That's the number I was thinking.

[greenmonster]

Try indexing plugs maybe?

[koko64]

 

[koko64]

IMG_1099 by Tony Kokonis, on Flickr[

Regular DPR8EA-9 0.9MM gap, DPR8EIX-9 with 1mm-1.1mm gap. Same jetting. Dark area on Iridium plug is a shadow from the camera flash. Regular plug is black all the way down the porcelain, Iridium plug porcelain is a cappuccino colour all the way down. Motor felt good with both plugs, the Iridiums a little smoother and more responsive and of course less chance of plug fouling.