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Resident rocket scientist
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Discussion Starter · #1 ·
I'm running a stock TT conversion at 6 psi on NGK coppers BCP7ES, so they are the correct heat range. What gap are you guys running? I'm running the gap specified in the manual : .040. I'm getting a lot of knock under boost and suspect that this may be due to my spark plug gap as some helpful people have pointed out in another thread.

Any help is appreciated.
 

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I run .028 gap with NGK's one step colder. I get spark blow out badly at anything above .032. With a smaller gap your idle won't be quite as perfect as stock gap, but it should drive and boost fine.
 

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I love her▼
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3000 Hybrid is right. I run .030 so yea somewhere between 0.028 and .032 and you should be fine. Also how are your SMIC's doing? If they are getting heat soaked then that could also be contributing to the knock. I am going FMIC cuz I am tired of dealing with heatsoak, boost leaks and all that rubber tubing lol.
 

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Resident rocket scientist
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Discussion Starter · #4 ·
3000 Hybrid is right. I run .030 so yea somewhere between 0.028 and .032 and you should be fine. Also how are your SMIC's doing? If they are getting heat soaked then that could also be contributing to the knock. I am going FMIC cuz I am tired of dealing with heatsoak, boost leaks and all that rubber tubing lol.
I am running the stock FMICs but I don't think heat soak is the problem since the knock occurs even when the motor is cold (albeit even more when it is warm).

I don't know - .030 seems pretty small for a stock conversion on 6 psi. I was considering trying .035ish which is a little smaller than the minimum suggestion in the shop manual.
 

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Cabana Boy
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NGK's at .028. I had Iridiums at .031 and that worked, but I had tried .035 previously and got blowout at high boost. gotta tell yeah, first time it happened, scared the bejesus outta me....
 

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Discussion Starter · #7 ·
Well hell, if that's what's working for you guys I guess I'll try it as well. It just seems so small.
 

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og
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i run my plugs gapped at .030, any larger and at 15+ psi blowout occurs. this is with 13t's. currently coppers, once i get done tuning i'll be changing to the ngk irridium ix's and the gap will stay the same, .030.
 

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H to the izzO
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Tyla, on 6psi I'd say shoot for .035. If you still get blowout, regap it down to .032 and try again. On 6psi, I run one step colder NGKs at .040 without blow out.
 

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Quit while you're ahea
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Tyla, on 6psi I'd say shoot for .035. If you still get blowout, regap it down to .032 and try again. On 6psi, I run one step colder NGKs at .040 without blow out.
Old thread my friend. I put the link in someone’s thread that wanted help with gap and someone posted in it.
 

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og
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SOHC you in the FACE
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I want to point out that though you might not feel spark blowout, it starts happening before you feel it.
My 516whp pull was made after we noticed a very jagged hp line. I went from .032 to .025 (to not waste time on the dyno) and it pulled smooth. I didnt feel any blowout. I currently am running a .032 on my junkyard motor and 24psi = scary spark blowout that makes you think the engine blew up.
My guess is that it was blowing out at less boost but I couldnt feel it.
And holy crap, I posted this in the wrong "old" thread :p
 

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Ninja Performance
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I'm running a stock TT conversion at 6 psi on NGK coppers BCP7ES, so they are the correct heat range. What gap are you guys running? I'm running the gap specified in the manual : .040. I'm getting a lot of knock under boost and suspect that this may be due to my spark plug gap as some helpful people have pointed out in another thread.

Any help is appreciated.
Actually 6 are the proper heat range. You bump up one range colder for every 75-125hp. You are not there. So you should use 6's.

At 6psi there is no reason, except weak ignition parts, that you can't run 32 gap or even larger. Even 40 shouldn't be an issue at 6psi.

-Chris
 

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Excuse me for butting in on the conversation but since the topic is spark plugs I was just curious what are the symptoms of bad gapped plugs like too high or too low, I don't own a TT its just NA but I have iridium IX's with a few mods on the engine. The manual says .039-.043 but when is it ok to make the gap less or higher?
 

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Ninja Performance
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