Denso Iridiums

I had NGK-R's in and decided to get new plugs... I checked around for the NGK bpr7es's but none on hand... I was talked into getting the iridiums and was told they were even better than the NGK's by a supposed "turbo" guy.... so anyways I put them in and on my drive home it accelerated nice and smooth until I boosted over 8 psi. When I hit 8+ the engine started missing/shuddering... at any RPM...from a stop or at highway speeds... They are gapped at .039-.040. Do I just need to gap them tighter? I was told that for the NGK's I should gap them at about .030...
Thanks for any help...otherwise i'm putting in the old plugs!!!! f*ck denso!!!! lol

You have to be very careful gapping iridiums. I've never used them, but I have heard that the center electrode is hard enough to penetrate the surface of the plier type gapping tools. Using a feeler guage I'm sure you could do it. Platinums are a big no-no on turbo motors. I think iridiums are ok though. You already ahve them, might as well test them out for me. Drop the gap to about .028 and see if the stutter goes away If ot doesnt, get some regular NGKs.

I thought that too small of a gap would be bad... like too big of a gap is bad...?
your right... the tips are hard!!! I used a dial caliper and an old fashioned checker guage... I know... be careful the tips can break!!! lol I'll try the .028 in the morning...if it doesn't work do I have a chance of returning them? The guy said they would definately work!!! I even asked him again if he was positive!!!

He doesnt know the correct gap for your car, stock is 28-31 ;) 40 is for non turbos. Yes, he's an assclown.

Too big of a gap, the spark will blow out under boost, and that is the source of the misfire you are experiencing. If I run larger than a 26 gap, the car wont even run at WOT.

wow.... The NGK-R's I was using has the two arcing spots/ electrode is exposed to the cylinder... the gap for those are about.041 for both points on each side of all plugs and it never felt like a misfire... that and they had a reddish brown coating on them...never seen that on any of my plugs in the past....just the basic black...non turbo cars/engines...

The balance is between a small gap that sparks well under boost, but doesn't provide much ignition spark, and a wide gap that gets doused under boost, but would ignite well on an N/T. 0.028!

OK I regapped from.038 to .030 and it runs better but still has stutter but only about half as bad... i'm gonna drop it to .028 and see what happens.

OK I regapped plugs to .028 and it runs alot better... even the A/F guage reads alittle more to the rich side..but still lean...
I did notice a very small miss here and there.. maybe I should gap at about .027 .?.?.?
As for the iridium plugs... they seem to be pretty nice.

Speaking of gapping. On a N/T what should they be gaped at.(forgot to gap them when i put them in.)

OK I regapped plugs to .028 and it runs alot better... even the A/F guage reads alittle more to the rich side..but still lean...
I did notice a very small miss here and there.. maybe I should gap at about .027 .?.?.?
As for the iridium plugs... they seem to be pretty nice.


Try 27, sure. But the more power you make, the more trouble they will give you. Might as well get your moneys worth if it works though! Good work.

NT should be gapped at .045-.05

i was running iridiums for about 4 months and they were ok... but now i'm going back to bpr7es...

I had some NGK Iridiums for a while and they worked great. Smoother idle than the coppers-- I eventually swapped them for some BPR7ES ones, though, cuz I wanted to go one range colder and didn't feel like shelling out the coin for Iridiums again.