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Thread: what plug gap / boost psi are you running?

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Posts: 31-40 of 40
2014-06-05 14:14:07
Everyone should post what compression, ECU and Ignition system they are using or this is all useless. A stock mechanical DE distributor is going to need a lot less gap than a AEM with independent coils.

99' DE totally stock (ecu/dist/comp) 9.5:1 20psi BKR7EIX .018 gap - At it's limit gets blow out at certain RPM's
99' DE AEM EMS4 with 4x LQ9 coils 9.5:1 24psi BKR7EIX .25 gap - No blowout yet going to gap higher
2014-06-06 01:52:07
With my last ignition setup I was running for the last couple years, I never got a hint of blowout. AEM Twinfire CDI with GSXR1000 coils, AEM standalone. 700+whp and no issues even at .030" gap, My 2.2L VE-T with 12.5:1 compression on a 6262 didn't have any blowout either with a .030" gap on the bosch copper 8 heat range plugs. I don't think it was possible for the ignition system I had to misfire due to being unable to produce a spark. LOL! Very solid and reliable ignition setup. Cheap and simple as long as you have a standalone to run it
2014-06-10 01:30:42
My 9:5.1 de+t motor was breaking at higher rpm up gapped at .030 on 15psi. Re-gapped to .025 and no more blowing spark issues.
2014-06-15 15:10:58
If I very slowly/gently increase my RPM I notice towards the end of the RPM band (6k+) the car starts to back-fire a little and sounds like it's breaking up. Would you notice this without boost as well? Does that mean I need to close my gap or is this normal behavior? I don't really notice this under boost. Gap is at .028
Last edited by gomba on 2014-06-15 at 15-12-46.
2014-06-16 01:55:46
Misfire at high rpm is not always blow out. I had to increase the gap on mine from .028 to .032 to prevent misfires.
2014-06-25 06:31:55
Heat range 8 spark plug part # 4554. NGK non resistor. I've used them with MSD ignition boxes without any issues with EMI. They have the same case as the BK series plugs but a non-projected tip. Best part, they are easily found at Autozone and are pretty cheap.
2014-06-27 10:08:12
Originally Posted by LOUROK
Originally Posted by Will
Originally Posted by Coheed
Oh boy I wish I had saved my old dyno graphs. I had the gap set at .038" and did a pull on high boost. I was making over 10lb ft of torque consistently across the entire band, and more in some places, but the spark blew out at 5000rpm.

If it would have kept going I would have made over 460whp :o

I gapped it down and the torque dropped a bit, and small adjustments have had little effect on any dynos since. Dropping from .038 to .028 made a pretty good difference on the dyno though.

That is very interesting. I always noticed my turbo car felt better at higher gap until it started bowing the spark out.

I am curious about the reasons for this, perhaps more rapid combustion because the ignition point is larger and thus spreads faster for a more complete burn.

Same experience here. Larger gap, smoother idle , car felt more put together. Yes I know this thread is old

Old threads FTMFW. I think i always found the best balance at .028 on high boost (GTI-R setup on my 9.5:1 stock lowport DE with S4 cams).

If you guys haven't already, you should check out the thread that @Vadim did on "half gapping" or whatever it's called. I did it recently and really liked the results on my stock DE in the NX at .044" gap.
2014-06-27 19:17:59
I use either BKR7E's or BKR7IEX (iridiums), sidegapped. On OBD1 ECU with NEMU, using Roller Rocker (and 99 SE-L) distributor. I'm able to run .045 gap at 10 psi with no breakup. Granted it is much more difficult to measure a gap of a sidegaped plug, thus it could be .040.
2014-06-27 21:13:44
I use either BKR7E's or BKR7EIX (iridiums) have the IX plugs in right now.
Gap is currently ~ 0.030 and at this gap I'll run anywhere from 8 - 17psi...
Even though when boost is turned down, I should open the gap...

I run S15 coil on plug
2014-06-28 14:14:09
Once I switched to the S15 coils I was able to open the gap up back to normal N/A gaps. 1.1mm or 0.035" again at 11 psi.

Originally Posted by Ken's
Originally Posted by BenFenner
I'm at 0.028" for 11 psi (might as well be 15 psi).

What exactly do you mean by that statement?

Super late reply...

I push about the same amount of air into the cylinders at 11 psi that most do at 15 psi.
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