Spark Plugs For R34 Gtr 1.2bar Of Boost

[flyz33]

Hi guys,

I have the dreaded mis firing problem with my GTR. I will be looking at replacing my coil packs and will be replacing my spark plugs at the same time for good measure.

I have done the searches and read the spark plug thread but I'm still confused as to what to run??? I'm hoping a GTR owner could point me in the right direction ie part number or plug

At the moment the car has HKS2530 turbos and running about 1.2Bar of boost. Based on what i have read, I want to run the NGK copper spark plugs as I dont mind changing out my plugs every 10,000kms (weekend car).

Any help would be greatly appreciated.

Thanks.

[Wacky Dee]

just get the NGK coppers .. heat range 7 if up to 270rwkw or heatrange 8 if higher, I think.

BCPR7ES or BCPR7ES-11 (I think)

I'd get the latter which is pregapped to 1.1mm and get mechanic to reduce gap if you get a misfire at that gap size, but you should be fine with 1.1mm gap if you're changing coilpacks (plus more power/better fuel economy over lower gapped plugs)

Everyone will tell a different story/experience on the gap sizes and most ppl will recommend .8mm (ie. "BCPR7ES") plugs with more boost ... but some people run plenty of boost with even a 1.1mm gap and no misfire at all. Bigger gaps gives you a better spark, more power etc

Edited July 18, 2009 by Delta Force

[flyz33]

thanks Delta Force. Pulled out the plugs from my car and they were the NGK copper V power ones. So I replaced them with the same ones heat range 7 gapped to 0.8. Also did the quick fix on the coilpacks (tapped them up + silicon). Unfortunately the missfire is still there. Under WOT the car will feel like its hitting limiter at 5k rpm and only hitting 0.6 Bar of boost.

Perhaps its time for some splitfires or does anyone know what could be wrong here?

Cheers

[GTRPSI]

I had a similar problem with mine, im running 1.6bar.

Dropping the plug gap down to .7 made a big difference.

Problem was solved with a new ignition pack (on the rear top of the engine).

Will rev out now without a hint of a miss.

Hope this helps you.

Edited July 18, 2009 by GTRPSI

[flyz33]

I had a similar problem with mine, im running 1.6bar.

Dropping the plug gap down to .7 made a big difference.

Problem was solved with a new ignition pack (on the rear top of the engine).

Will rev out now without a hint of a miss.

Hope this helps you.

thanks man. Yeap looking to get some splitfires, hopefully that solves the problem. I guess the coilpacks are about 10yo now so would be worth replacing. What heat range are you running? We gapped them down to 0.8 as recommended by most people on here and the guys on the UK GTR forum.

[Wacky Dee]

I had a similar problem with mine, im running 1.6bar.

Dropping the plug gap down to .7 made a big difference.

Problem was solved with a new ignition pack (on the rear top of the engine).

Will rev out now without a hint of a miss.

Hope this helps you.

did you try going back up to standard gap (1.1mm) after getting a new ignitor? From my understanding, lower gap is a cheap hack only needed with old/factory coilpacks.. If I were to get new splitfires/ignitor first thing I'd try would be standard gap.

[flyz33]

did you try going back up to standard gap (1.1mm) after getting a new ignitor? From my understanding, lower gap is a cheap hack only needed with old/factory coilpacks.. If I were to get new splitfires/ignitor first thing I'd try would be standard gap.

In saying that though, it wouldnt hurt to run new coil packs with a smaller gap?? I know larger gap = more spark = more power but as you increase boost I was reading in another thread its actually better to have a smaller gap? I'm still learning all this stuff, quite confusing as there is so much info and sometimes its contradicting haha

[Munkyb0y]

ive heard that too. but i cant understand why a smaller gap is required for higher boost if you can run the bigger gap at desired boost with no missfire issues.

Edited July 19, 2009 by Munkyb0y

[GT-R32]

Can someone please advise where we can buy these plugs online?

[Wacky Dee]

kudos motorsports I think has them .. also most tuners/mechanics do too.

In regards to the smaller gap with higher boost .. I think the higher boost can 'blow out' the spark if its high enough, but I don't believe 1.2bar/18psi would do that, I could be wrong. I'm running 12psi on factory coilpacks and 1mm gap with no missfire.

[Munkyb0y]

obviously if your spark is being blown out, ie. your coils arent up to the job, then you would gap down as most ppl do on stock (old) coils.

but if there's no issue with spark blowing out at 1.1mm, THEN what is the purpose of running a smaller gap?

the reason i find this perplexing, is that its been recommended by knowledgeable people.

[GT-R32]

kudos motorsports I think has them .. also most tuners/mechanics do too.

In regards to the smaller gap with higher boost .. I think the higher boost can 'blow out' the spark if its high enough, but I don't believe 1.2bar/18psi would do that, I could be wrong. I'm running 12psi on factory coilpacks and 1mm gap with no missfire.

Thanks very much for that. I went with the smaller gap plug since the car is tuned to 1.45 bar.

[GTRPSI]

My coil packs are stockies, i gaped down and the misfire improved but didn't totally disappear.

Checked the coil packs for a lightning show at night and they looked fine, no arcing.

It totally went away after i changed the ignitor module on the rear cover, no i didn't go back to open the gaps again as she was purring like a kitten to well over the redline.

Next weekend ill pull a plug out, 1 heat range colder from what i remember last i had them out.

Edit, shes been fine for the last 2 years like this but just develop a misfire at 1500-3000 rpm 2 weeks ago. It corresponded with the idle speed going up to 1400 rpm.

Solution...replacing the throttle body and intake gaskets right now, they were blown.

Edited July 20, 2009 by GTRPSI