Copper Plug Gaps

[LotusGTR]

Ok, I've found some info but not all I need. I'm running a fair bit of boost (1.5 bar) and will shortly have new coils, which are being replaced due to a misfire. It has a roughish idle so whilst we're in there may as well flip the plugs over.

So to the question, how should they be gapped before they get thrown?

Thanks.

[PM-R33]

If they are NGK coppers and have no number on the end of the part number (ie BKR6E etc) then they are allready pregapped to .8 just leave them at that.

[LotusGTR]

BCPR7-11 ngk

I've just found out these are the plugs currently in the car which I would intend replacing like for like.

Still 0.8mm gap?

[abu]

The '-11' means there gapped to 1.1

You can always get BCPR6ES which are pre-gapped to 0.8 or even a range colder, BCPR7ES which are also pre-gapped to 0.8. Anything with say '-11' on the end means there gapped to 1.1. You can get BCPR6ES-11 as well but that means you will have to re-gap it your self

Anyways, just get some BCPR7ES as there already pre-gapped to 0.8 if you can't get them then get BCPR7ES-11 and use a gauge to re-gap them to 0.8

[LotusGTR]

The '-11' means there gapped to 1.1

You can always get BCPR6ES which are pre-gapped to 0.8 or even a range colder, BCPR7ES which are also pre-gapped to 0.8. Anything with say '-11' on the end means there gapped to 1.1. You can get BCPR6ES-11 as well but that means you will have to re-gap it your self

Anyways, just get some BCPR7ES as there already pre-gapped to 0.8 if you can't get them then get BCPR7ES-11 and use a gauge to re-gap them to 0.8

Thanks Abu. Those plugs are the ones my tuner put in the old girl when I did a full rebuild. I'm not knowledeable enough to second guess his choice so I'm going straight back for what he used originally, unless there is something better on the market now (twas a couple of years ago).

You seem to be pursuing the idea that a 0.8mm gap is preferable to the 1.1mm on the plugs I've got now? Is that ture? Any reason why?

[Munkyb0y]

you may find that your missfire is caused by the 1.1mm gap. If you were to put 0.8mm gapped plugs in there, the problem might well be solved.

if you can run a 1.1 gap on the new coils without missfire, that's ideal. generally, the larger gap you can maintain, the better the combustion. ie, bigger bang.

if you need to run 0.8 to avoid missfire, thats fine, and very common. going lower than that is generally something to avoid.

Edited November 24, 2008 by Munkyb0y

[LotusGTR]

you may find that your missfire is caused by the 1.1mm gap. If you were to put 0.8mm gapped plugs in there, the problem might well be solved.

if you can run a 1.1 gap on the new coils without missfire, that's ideal. generally, the larger gap you can maintain, the better the combustion. ie, bigger bang.

if you need to run 0.8 to avoid missfire, thats fine, and very common. going lower than that is generally something to avoid.

OK, well for better or worse I've got new coilpacks going in as well as plugs. With new plugs, I'd expect that the 1.1mm gap will be fine given that on old coilpacks and new plugs (around 2 years and 10,000kms ago) it all ran fine.

Cheers.

[abu]

Yep that's pretty much it

In my R32 I used to get miss fire running 1.1 gap with about 18psi but always ran good with pre-gapped BCPR6ES plugs @ 0.8mm. At the moment in my R33 GTR I run near new splitfire coils and 0.8mm gap again, runs fine without any miss fire or starting issue but it's only running around 13 - 15 psi

I might try the BCPR7ES-11 plugs just to see how it runs but nothing worse than putting them in and it missfiring then ripping it all apart again to regap them to 0.8

Big gap can cause miss fire at higher boot/RPM and also make it harder to start the car when cold, 0.8 is the safer bet in my opinion especially if your running 1bar +

[R31Nismoid]

0.8mm gap for high boost applications regardless of coils

[LotusGTR]

0.8mm gap for high boost applications regardless of coils

Yeah, all roads are leading to 0.8mm. My mechanic (not tuner) is saying defo 0.8mm

[bubba]

As a rule, I always check the gap on pre-gapped plugs before I put them in. Lately just been getting BCPR6ES-11's and gapping them back down to 0.8.

[LotusGTR]

Plugs have been gapped to a poofteenth less than 0.8mm. That and the coilpacks have sorted the misfire. Phew.

[R31Nismoid]

Good to hear

[LotusGTR]

Good to hear

Thanks for the assistance. There is also a lot less popping on the over-run, and I'll bet less flamage too........It kind of seems tame now, but at least it's making powah again.

[PHA71L]

.8 FTW!