Jump to content
SAU Community

Plug Gapping and Misfiring

adam 32

By adam 32,
in Engines & Forced Induction

 Share

Recommended Posts

adam 32 Grand Master

adam 32

Posted
Posted

i was gettin a misfire on high boost before, so i put in new plugs gapped to 0.76mm (damn non-metric feeler guages:D )

anyway, now it pulls hard all the way to redline on 1bar boost, but it seems to misfire at idle?! (sounds like ive got cams!) is this because im now running too small a gap? or is this what you sacrifice in order to get a reliable spark under high boost?

thanks

adam

Link to comment
https://www.sau.com.au/forums/topic/6160-plug-gapping-and-misfiring/
Share on other sites
rev210 Grand Master

rev210

Posted
Posted

Could be the smaller gap and worse still if you have installed a colder heat range of plug.

The smaller gap/colder plug provides better combustion for top end (as per the reason you did it) but, provides poor combustion at idle. The plugs will have less life in them as well.

Best thing to do is practise changing plugs, so you can change to a colder set for race use and leave a nice warm setting for the street. Poor combustion also shortens the life of the engine BTW.

adam 32 Grand Master

adam 32

Posted
  • Author
Posted

but theres only poor combustion @ idle so should be sweet:P

i dont fancy changing plugs THAT often, took me long enoug thanks to nissan's coil packs :) the plug is 1 heat range colder, so thats gunah add to it as well.

i guess im sacrificing the bottom end for top end, as it seems to go with turbo cars when they make big power.

rev210 Grand Master

rev210

Posted
Posted

The plugs foul at idle, and get cleaned up when you floor it.

They just won't last as long as your old ones. Why not run the gap at 0.9 or so, with a colder range plug I'm sure you won't be down any power and it will give back the idle perhaps.

Zahos Mentor

Zahos

Posted
Posted
0.9 on a colder plug should be fine.

Nope! I've tried numerous combinations with heat range and gap, and what I'd recomend for street use is a heat rating of 6, and a gap smaller than 0.8mm. If you have an aftermarket ECU, or a SAFC, then this recomendation doesn't really apply to you...

With stock ECU, b/c the mixtures can get really rich, you need a warmer plug that can burn some of the carbon deposits off the plug. The colder plug will not last long, as it will get fouled very quickly (a couple of weeks), and will need to be pulled out to be cleaned. A warmer plug will go a lot longer before it needs a clean.

As for gap, I've tried

0.9 with a colder (7) plug, 0.8 and 0.7 as well. I found the smaller gap to be the best....

But like I initially said, a warmer plug and smaller gap is best for street use..

I'd say NGK BCPR6E (NO S). This has a heat rating of 6, and the v groove. Gap this anywhere between 0.65 and 0.75, and your Line will run much better (remember, only if you nave stock ECU meaning rich mixtures). At this configuration the 5000rpm misfire on the R33 happens much less!

I only see it when I have been driving the car for more than 30 mins... weird!

Zahos

JH32 Grand Master

JH32

Posted
Posted
Originally posted by Zahos

But like I initially said, a warmer plug and smaller gap is best for street use..

I'd say NGK BCPR6E (NO S). This has a heat rating of 6, and the v groove. Gap this anywhere between 0.65 and 0.75, and your Line will run much better (remember, only if you nave stock ECU meaning rich mixtures).Zahos

Zahos ... does this apply to R32s as well??

Zahos Mentor

Zahos

Posted
Posted

OK then, well I guess the same theory applies to R32's as well. But no matter what, if u have stock management, and higher boost, you will see this problem. What I suggested merely deminishes the magnitude of the problem, and will prolong it from creeping up. I have had my plugs in for 2 months now, and I dont see the problem very often (running 0.7 bar ~10psi).

rev210 Grand Master

rev210

Posted
Posted
Originally posted by Zahos

Nope! I've tried numerous combinations with heat range and gap, and what I'd recomend for street use is a heat rating of 6, and a gap smaller than 0.8mm. If you have an aftermarket ECU, or a SAFC, then this recomendation doesn't really apply to you...

As for gap, I've tried

0.9 with a colder (7) plug, 0.8 and 0.7 as well. I found the smaller gap to be the best....

But like I initially said, a warmer plug and smaller gap is best for street use..

I'd say NGK BCPR6E (NO S). This has a heat rating of 6, and the v groove. Gap this anywhere between 0.65 and 0.75, and your Line will run much better (remember, only if you nave stock ECU meaning rich mixtures). At this configuration the 5000rpm misfire on the R33 happens much less!

I only see it when I have been driving the car for more than 30 mins... weird!

Zahos

Adam's got an HKS AFC thingo.

Like you I run the stock rated 'warm' plug. Regardless of gap they (warm plugs) will have a nicely cooked electrode in no time with a setup like Adams with revs and tO4 style boost.

adam 32 Grand Master

adam 32

Posted
  • Author
Posted

the problem doesnt seem to be as bad anymore actually. im not sure why...

even if it didnt rectify itself i was happy to run a 0.75mm plug gap as it pulls very nicely through top end

jimi if ur running the VG30 at that sorta boost (which u should :D) then run the same plugs as me. i think theyre BKPR6ES or something

Black33 Proficient

Black33

Posted
Posted

what gap do u guys think I should run:

I have -

full exhaust (dump, front and rear)

10 - 11psi boost

pod

cold air intake

Also, how long does it take to remove all of the stuff under the plastic panel on the engine head to get to the plugs? is it hard (i got to it and then stopped)?

thanks

Zahos Mentor

Zahos

Posted
Posted

Try 0.7 or even 0.65+

A good spark plug (copper) is NGK BCPR6E

Platimuns r good, but not worth the money, as the only benefit they have is a longer life span. I dont plan to leave plugs in there that long anyhow, as they foul easy when running rich....

R32 Zilla Community Regular

R32 Zilla

Posted
Posted

I have the same problem with my r32

Running 19 psi through a hks gt2535 and a rechipped computer it misses at about 5000 rpm.

Have tried lots of different things to fix it with no luck yet.

Iam now running a gap of .65 and when i did this it developed a miss at idle (like adam32) . This does not worry me as all i want is for it to rev cleanly to redline.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      R32 Sedan - Grip and Drift (have my cake and eat it too build)

      By Duncan · Posted

      Ahh got it. Well maybe install a drain for the catch can somewhere down low and accessible like a wheel well too....
    • MBS206
      Help Understand GTT Boost Setup

      By MBS206 · Posted

      Before you blow your car up, have you checked you've made all the correct modifications to the wiring if you're still using the RB20DE loom?   Some things to look at: The pin used for the map sensor on the RB25DET, is the same pin used on the RB20DE for the Ring Gear Crankshaft Position Sensor, no idea what you've got it plugged into now. The turbo pressure control valve solenoid you're talking about on the RB25DET, the same pin is used for the Variable Air Intake Control Valve on the RB20DE.   The factory manual has the wiring pinouts in it for you to check everything. It also has the diagnostics process to read codes out. In addition, there's a great table that shows what sensors and what actuators not functioning will relate to which signals. And Nissan confirm the as everyone else has from experience, the Solenoid being disconnected won't cause a fuel cut. However, the turbo pressure sensor being missing / wrong, WILL cause a fuel cut. https://www.nicoclub.com/service-manual?fsm=Skyline%2FR34-Workshop-Manual-English.pdf
    • Butters
      Compressor flow comparison table

      By Butters · Posted

      I've been hunting info on the G Series II - this is best I have found so far(Link below). Still waiting on the G35-1150 comp map, kind of very keen   So how do we go about getting precision on that little table of yours ?   https://turbosbytm.com/sites/default/files/product/technical-info/Garrett-G-Series-II-Product_Flyer 25 30 35_1.pdf  
    • CRSKmD
      R32 Sedan - Grip and Drift (have my cake and eat it too build)

      By CRSKmD · Posted

      yeah I get ~0.6L per session into the catch can. very ethanoly. It ends up overflowing out the breather of the catch can on circuit days too even with a 2.3L capacity catch can and I only drain out ~0.6L max. So every session I have to come in and drain the catch can, which is a hassle. So this is me cracking the shits and doing everything I can without removing the motor (back of head sump drain/breather and oil restrictors off the table). plans short term are: full length splash plates remove oem cam cover baffle add foam and reinstall at -10 or -12 AN fittings to the side of the cam covers down to the sump (luckily I already have fittings in the sump) Yes the ~340,000km unopened motor is probably not helping things
    • Duncan
      R32 Sedan - Grip and Drift (have my cake and eat it too build)

      By Duncan · Posted

      I'd use any fuel safe foam....mine went in 15 years and 15 rebuilds ago, still getting reused I'd have to say I don't understand swapping to studs to fit a particular baffle unless you are having a massive blowby issue, and even if you are addressing crankcase not head breathing is probably the next step.
×
×
  • Create New...