Turbo Spark Plug Gap

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david58
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Turbo Spark Plug Gap

Post by david58 » Fri Jun 26, 2009 9:45 am

When using electronic ignition on a turbo should the gap be wider?
Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.

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Post by miniman82 » Fri Jun 26, 2009 10:21 am

I found that if I opened my gap past .035", it wouldn't run right at idle. It was lumpy and sometimes stumbled, but I couldn't tell any difference once under boost. kinda strange. I have them at .030" now, which works great.
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Post by MinamiKotaro » Fri Jun 26, 2009 12:13 pm

Mine like around .020. .030+ and it cuts out under boost.
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Post by Howie » Fri Jun 26, 2009 1:14 pm

I run a Billet MSD dizzy, MSD6 BTM, MSD wires and Blaster 2 coil, and set my Bosch W8AC plugs to .035. Street only Ghia.


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Post by Turbo_Manx_Maniac » Fri Jun 26, 2009 6:21 pm

Howie wrote:I run a Billet MSD dizzy, MSD6 BTM, MSD wires and Blaster 2 coil, and set my Bosch W8AC plugs to .035. Street only Ghia.


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I run almost this same setup (6AL & blaster 2), I've tried everything from .020 to .040 and it made no difference. Settled on .035".

I think a turbo requires a smaller gap, not larger. The gap on my wifes Honda is 1.1mm or ~.043", if I added a turbo I would close the gap by at least .010".
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Post by seabeebuggy » Fri Jun 26, 2009 7:26 pm

mine liked a smaller gap. .020 keeps the boost from blowing out the spark.
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Post by Howie » Fri Jun 26, 2009 8:11 pm

There are so many variables, it would be helpful if everyone told what ignition they are running along with the gap that works for them.


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Post by david58 » Fri Jun 26, 2009 8:38 pm

Howie wrote:There are so many variables, it would be helpful if everyone told what ignition they are running along with the gap that works for them.


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That is a great idea. I don't have a turbo, a friend does and he was told by the guy that built the engine and turbo to gap the plugs at 20. It being electronic ignition I thought the gap needed to be wider. But as has been pointed out in this thread too wide and you can have miss-fires from the boost blowing out the flame.
Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.

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Post by MarioVelotta » Sat Jun 27, 2009 12:36 am

I run edis and a gap of .032" at 14lbs boost no problems.
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Post by WickedWagens » Sat Jun 27, 2009 12:51 am

What plugs, brand and heat range, is everyone using might be helpful also.

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Post by shawn63deluxe » Wed Jul 01, 2009 3:40 am

I run bosch W8AC plugs. They came to me in my turnkey engine gapped at 0.048-0.050" the engine would idle roughly and head temps were a pain, even light load on the throttle would see head temps rising higher than I would like. I re-gapped the plugs to 0.030" and now have 350' head temps no matter what. Idles smootly at 1000rpm. Msd dizzy, redline weber ecu, blaster 2 coil and msd leads.
I was amazed how a little work could make such a difference.
Last edited by shawn63deluxe on Wed Jul 01, 2009 10:03 am, edited 1 time in total.

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Post by david58 » Wed Jul 01, 2009 6:27 am

shawn63deluxe wrote:I run bosch W8AC plugs. They came to me in my turnkey engine gapped at 0.48-0.50" the engine would idle roughly and head temps were a pain, even light load on the throttle would see head temps rising higher than I would like. I re-gapped the plugs to 0.30" and now have 350' head temps no matter what. Idles smootly at 1000rpm. Msd dizzy, redline weber ecu, blaster 2 coil and msd leads.
I was amazed how a little work could make such a difference.
With wide gapped plugs head temps rise, so does the gap have a effect on timing?
Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.

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Post by SUbuggy » Thu Jul 02, 2009 3:39 pm

spark plug gap is controlled by how "powerful" your ignition coils is. As cylinder pressure increases (boost) it becomes harder to jump the gap, this is the reason an ignition system works OK at .035 but need to be .025 (or less) as boost pressure rises. If you find you are having misfires, it's not the boost, but YOUR WEAK ignition system based on the running conditions of your engine.

overly-rich mixtures also are harder on the ignition system, super high engine speeds (less physical time to charge the coil), and things like a pertronix module DO NOTHING for spark energy, all they do is keep from wearing out and having to change points.

as for head temps, the large gap was probably promoting misfires, that was the reason for the high head temps. by closing the gap down, you made for more consistent igntion events ie a better running "smoother" engine at idle.

The OEM's run massive .060 gaps, but they do this in conjunction with a very powerful multi coil ignition. mainly due to emissions, ragged edge lean condition promote mis-fires. by having a very powerful, long duration inductive spark, this helps promote good igntion events without misfire.

Spark plug gaps do not MAKE hp. all they are there for is to START the combustion process. True, you might find 1% by indexing, fine tuning a gap for your particular engine, but for the most part, a lot of HP is there to BE LOST by a WEAK ignition system package, not just the gap.

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Re: Turbo Spark Plug Gap

Post by GARRICK.CLARK » Sat Aug 11, 2018 11:48 am

bump

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