Spark Plug Gaps

[Birds]

Engine is an RB25DET. Relatively stock bar an exhaust and cold air intake. Just bought some NGK Iridiums (BKR5EIX-11) for my 100k service and was wondering whether I should just whack them in (and by that I actually mean very carefully) with their standard 1.1mm gap or see if anyone has recommendations on gap size. I see alot of 0.8mm gap fans out there. Was this to resolve misfire issues or is this just a good recommended gap? I'm no spark plug expert so I'm pretty clueless when it comes to gap size and heat etc. I just know that Iridiums have served me well in the past. I do have an occasional misfire high up in the rev range (talking 6500rpm), but I have not removed the existing plugs to see what gap size they have.

Also, while on the topic, which igniter configuration did the R33 1.5 come with? Series 1 or series 2? I could do the non-lazy thing and check under my bonnet but the keyboard is easier. I plan on forking out for some aftermarket coil packs but I'm unsure of what I need to specify when ordering.

Thanks guys.

Edited June 23, 2009 by Birds

[Wacky Dee]

stick with the wider gap if you've got no missfire issues ... thing is, as soon as you put more than stock boost in it, you'll probably run into missfire so .8mm to 1mm gap is good there (for me .8 was no good ..would misfire constantly at idle and low revs)

Either way, the plugs you got are way too hot .. if you check the NGK catalogue they recommend heat range 6 as stock replacements. So if you've got 20-30kw more than stock I'd go for heatrange 7, but 6 would do too. Either way, 5 is way too hot. HTH.

Edited June 23, 2009 by Delta Force

[Birds]

Thanks for the advice, I'll put them in and see how I go I guess. Can always remove and re-gap.

Just checked the NGK catalogue and it recommends BKR5EIX-11. I do have plans to modify my engine, so will change to a colder range down the track but for now I think it should be safe. NGK will hear about it if my pistons start shredding away!

[blind_elk]

Either way, the plugs you got are way too hot .. if you check the NGK catalogue they recommend heat range 6 as stock replacements.

NGK website (and I'm pretty sure the cattle-dog) says 5s for a (stock) RB25DET.

[Wacky Dee]

hmm maybe the 25 neo is different, dunno ..just remember when i was looking at the catalogue for the neo it said heartange 6 as stock replacement..

[Wacky Dee]

from their website..

5/98 - 6/01 Nissan Skyline 2500 Turbo RB25DET

Spark Plug Part No.

Recommended Plug PFR6G-11

..but before 98 (presumably R33's ..) it shows 5's. Strraaaange.

[Birds]

Variable valve timing might have something to do with it running hotter?

[Rekin]

Depends on condition of your electrical side of car. Do you have a health battery? Coilpacks? etc

Alot of people drop sparkplug gap to 0.8mm once they push more than standard power because they begin to misfire. I used to run 0.8mm when I had dodgy coilpacks.

After replacing battery and coilpacks I put them back to the standard 1.1mm supplied.

Car is pushing 210kw atw and no misfiring.

However as you said that you have a misfire already at 6500rpm, Id probably try and go a bit under 1.1mm.

Perhaps buy a set of copper spark plugs and give them a shot at different gap sizes.

Coppers are much better in conductivity which make them better than iridiums, only issue is that they need replacing every 10k

Let us know how it goes.