My r33gtst is running 18psi and 247rwkw.

I have been using BKR6E plugs and just started getting misfire above 4000rpm.

The plugs have only been in about 12,000km. However, I have had a dyno tune and 1/2 a track day on those plugs. The plugs still looked ok.

The misfire is now completely gone and the response is back in my car. Heaps more power.

Replaced with the same NGK BKR6E.

I suggest changing every 5-7,000km.

Anybody know how long the iridiums last before a loss in power?

It's not the most fun job changing them but only takes me about 1-1.5 hours now..

If running less than 14psi you probably wouldn't get the misfire as quick but you are probably losing power by not chaning your plugs.

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did u gap them to 0.8 ?

Coppers have never really lasted longer than 10,000kms, and should be changed every 10,000 or sooner, just do them everytime you change the oil.
1.5hrs to change plugs is a bit of time though, i could do it faster on my 25 and i dont set a blistering pace... and the 26 is faster again for obvious reasons.


Iridi's generally dont last as long as they say unless in a stock car.

But with tuned cars, more boost, higher temps and everything else associated etc etc, the reality is they dont last anywhere near that.
So stick to coppers, change them at least every 10thou and live happily ever after, its pretty much a given, surprised you didnt realise that

the way i see it is that the coppers should be changed atleast every 10k, the iridiums say every 100k, lest just say that the iridiums only last 70k, the coppers are what, $2-$3 each, lets say $2.50, iridiums are about $15 each, so each change is costing you $15 for copper and $90 for iridiums, but you have to change the coppers 7 more times than iridium so really it cost $105 in coppers and a lot more time spent changing then, even lets say that you only get 60k out of iridiums the money breaks even but your saving a lot of time, even if you only get 50k they only cost $15 more and still save you a lot of time.

i know what i would prefer to be doing, and its not changing plugs all the time.

And this equation is assuming you do the coppers at 10k, which would probably be strecthing the life of them, where as 50k is not stretching the life of an iridium.

They would have needed changing after the dyno tune.

Platinum and Iridium plugs do last longer under normal driving conditions compared to copper but they all pretty much degrade as quick as eachother when put through heavy work on a dyno or on the track.

Depending on how often you go on the track the best bet is putting a new set of coppers in and let them cop the abuse of the track day, throw them out after and have a dedicated set of street plugs so that you can be confident you're not losing performance to over worked plugs on the street.

Irdi's wont last 50k, let along 100k in a well modified car, thats the problem.
Coppers take a beating for thier life whilst the iridi's will foul much easier. Do 10 cold starts with short drive in a row (ie, trip to the shops and back) and you can foul em that easily.

Say a fuel reg dies, in 50k, easily could happen, iridi's dead.
Fuel pump gets a bit tired, again, iridi's dead
So many things to destroy them, when what does it matter if your only using $15 worth of plugs

Soon as you kill one set prematurely of iridi's you've lost the money on them right then and there.
I killed a set after 20k (a few years ago now), never gonna do it again @ nearly $100 a set. Not worth it for a modified car.
Stocker = yeah probably much more viable and id go that route if it was.

lol ur worrying about $100.
never had an issue with mine and been using for some time.
I have checked them every 5k and so far no issues with the iridi's at all after 10k.
Personally for $100 every 10k or whatever I couldnt give a toss. Although now you can get them online much cheaper now

I just dont like handing over a kermit for something useless

Kill two or 3 sets on a year and your up for $250 or so, thats a few beers lol

I guess i've never noticed - running only 10psi before I think I got about 20k between changes, without even getting a miss.

Probably about 1-1.25h is realistic . But I doubt you'd get much quicker than that when you have to take off strut brace, intake pipe etc and then reinstall. I reckon a workshop would get you for a good 1.5-2 hours..

PS. BKR6E come gapped to 0.8mm. I checked them last time and all good. This time I didn't bother.

1+ hours to change plugs??? wtf are you guys on?

takes me 20 mins max, and yes i have a coil pack cover on, still with cross over pipe etc.

I run coppers, NEVER had a prob with them much prefer paying SFA for a plug rather then 120+ for 6 of them...

ok quick noob question... sorry to hijack thread..

but my r33gtst misfires like crazy aftrer 5000RPM.

I changed mine about 5000ks ago (the iridium ones) but it still does it...

how do i gap them to 0.8?

can it be the coil packs? its driving me crazy... just saps the power...

20min if you having a beer at the same time... LOL

Buy plugs that are 0.8 rather than regapping 1.1's (most 0.8's are the same plug number with a -8 at the end). Many misfire problems are caused by aged coils, spend $500 on a set of splitfires and you will be amazed at the difference.

On a side note, when I changed the plugs in my Toyota Hiace at 100,000km the guy tried to sell me Iridiums as they are the factory plug that Toyota uses due to the difficult location on the engine. I handed them back and bought a set of coppers and ran them for an entire 100,000km without any issues at all. I've now run a second set of coppers for 103,000km without any problems

i do that often

iv never taken off my intake pipe to do the plugs, if im hung over il use the lil worm bit at the end of my socket but its not a must, 20min easy !! bcpr6e gapped to .8 never looked back