Spark Plug Question

[Addisonc]

Hey guys so I just bought a set of BCPR6EIX iridium plugs for my new gtr. When I pulled out the old plugs, I thought they would be the stock plugs but they were actually BCPR6EIX's as well, and it seems like they'd been in there for a while. Anyways three out of the six plugs were kinda white, doesnt that mean the plugs are too hot? The other three just looked like they had regular wear on them, but arnt they all supposed to be in the same condition when the engine is running properly?
Umm soo I’m hoping its normal to have variations in plug condition.
The car has only been lightly modified and I dont know the horsepower, as I just got it.

Should I get heatrange 7 plugs instead of 6?
Should I just put the new plugs in and see how they do?

Also I read that i should use a 0.8mm gap, but the factory spec is 1.0-1.1mm gap. I was planning on using plugs with 0.8mm gap because they are better for boost aparently?
What do you guys think? Thanks for the help!




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[TW]

those pics are monstrous, try resizing

[frankiman]

keep the 8mm gap (could even go to 9mm)
basically, a bigger gap will produce a stronger and bigger spark, burning the fuel more efficiently
but, when boost pressure goes up, the spark has much more difficulty to travel through the higher density air

if you are running stock boost, go with a 9mm gap,
if you are running more than stock boost, than reduce gap a bit, 8mm is fine (i'm at 8.1mm/.032" for 15psi)

[NismoS-tune]

Bigger gap is better as frankiman says but you don't always have to gap smaller as you boost up. Some not so affordable options are to upgrade the ignition system into a stronger one so you still get maximum spark with a larger gap. A proven option is the HKS DLI (though I heard once that it did nothing on a G35 as it already had a kickass ignition system). A DLI can run you around $500 with it's harness. The splitfire, red or yellow coils don't really increase secondary voltages much (might see a few more whp with those) but they are cheaper than new OEM coils and decorate a little. An ignition amplifier is what the big gap plugs need.

Most people simply gap to 0.8 and do that. Others upgrade the ignition for more reliability/durability/performance but if you don't have extra cash to go upgrade crazy, forget the ignition till it breaks.

[Wingnut]

Napa stock number: 4091

NGK copper core "racing" plugs. About $5 each. Set the gap to .8mm That should cover you from stock to 20+ psi. AND, they are much more resilient when fouling, a few mis fires and you'll see your irids wont run right...

[frankiman]

but the NGK-R coppers (racing) plugs only last about 10,000km
thats what i'm using, and paying only 3$/plug

[NismoS-tune]

Napa stock number: 4091

NGK copper core "racing" plugs. About $5 each. Set the gap to .8mm That should cover you from stock to 20+ psi. AND, they are much more resilient when fouling, a few mis fires and you'll see your irids wont run right...

Hmm. What about over 20psi?

[Bossman]

NGK Spark Plugs USA

When you gap platinum or iridium plugs be careful not to damage the tip, use a pair of pliers to adjust (bend) the ground electrode, don't slide the gap gauge in/out the air space. You can even get plastic gap gauge too from crab tire believe it or not.

[Addisonc]

Okay thanks for the input guys, what do you guys think about only three of the six plugs burning white like that? Should I run a compression test? Or just run new plugs and check them regularly to see how they do?

[skaG]

about different color on the spark plugs, well there are a few things that you can check on, very common problem for bnr32 is intake manifold insulators failure, if this is the case your idle is a bit higher than normal so you know, yes different compressions might be the reason or three of injectors are getting tired(may be it's time to O/H injectors) if it's coils( I don't think it is) you can swap them and check them after a few hundred KM or simply 3 spark plugs are done, after all that's what I start checking with.
have fun & good luck

[Addisonc]

Okay thanks i'll check those things, that helps alot ! Any other ideas?

[GTR-Dad]

What's an intake manifold insulator? Seals?
Dan

[Addisonc]

Sorry, what does it mean to O/H the injectors?

[skaG]

insulator is intake manifold gasket & throttle chamber gaskets,

O/H is overhauling, may be only Japanese people use O/H abbreviation

[CelicaKidd_205]

Don't worry about the white on the tips. Canadian gas has an additive called MMT that does that to your plugs over time. I'd say a good 90% of the spark plugs I've changed looked exactly like that. If anything the other three look like they may be getting a bit of oil on them, or it might just be a bit of carbon build up. I would not recommend that you do any drastic measures right now. I would change all 6 plugs and check them again at the end of October (or when you store the car for winter, whichever comes first).

As far as gap goes, a smaller gap will give you a weaker spark, but it also puts less strain on your ignition system. The weaker spark may not be able to ignite a rich mixture (it may missfire on hard acceleration). A larger gap will give you a nice hot spark that will ignite a rich mixture, but it can increase the wear rate on ignition coils and can in extreme cases cause heat spots under lean conditions which can lead to detonation and piston and/or head damage.

I'd try to go as close to factory as you can, unless you have a fuel/ignition tune for a richer mixture, then I'd go with a slightly bigger gap. Going a bit smaller won't hurt. I don't think you will notice a difference if you leave the gap at .8mm, but like I said closer to the manufacturer spec is better.