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Forced Induction Spark Plug Gap.

Discussion in 'Powertrain' started by Barnacules, Aug 1, 2006.

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    Barnacules 100101101011011

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    Spark Plug Gap.

    I was talking to a knoledgeable guy today about forced induction, he drives a old Celica Alltrac pushing over 500whp. I told him that I was having problems with hesitation and missing under full boost (7-8psi). He says that its the spark plug gap that under boost the flame kernel can be extinguished. I was just curious what gaps people are running with there turbo setups here? Post them if you got them.
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    fishexpo101 Get Some

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    I was told by engine gurus many moons ago that if you convert any vehicle to forced induction, two main rules should be followed:

    1) To prevent / reduce the chance of detonation, a colder temperature spark plug MUST be run. Usually start with a two or three step colder plug and can work back to a one step at a time until you hit the correct heat range - you can always air on the side of safety and run a colder plug, running a hotter plug will only lead to problems. Run a set of plugs for a while, pull them and read them (lots of gray, black soot-like powerder or sometimes fuel fouled - plug too cold, if plug look white, shiny, blistered, sparkles like a diamond - plug is too hot).

    2) To reduce the tendancy for the spark kernal to be blownout, reduce the spark plug gap. How much will depend on the plug and boost levels. Try stepping the OEM gap from 0.044" to 0.035" to start and see how that runs. Adjust gap until max power and drivability is achieved. Gap closed up too much will run as badly as a gap that is too big.

    Plug wise - they say stick to plain single electrode plugs (ie copper plugs). You'll burn up a few testing out some thing and getting the tune straightened out. Fine-wire plugs like the OEM Iridium on the VVT-i 1ZZ-FE Corollas are suited for high RPM N/A engines - they don't recommend them for boosted apps, though I've seen people run them just fine.

    As a little tidbit - old drag car running on alcohol - the sparkplug gap was between 0.010" to 0.005".
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    Barnacules 100101101011011

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    Wow, thanks for all that info. I'll re-gap my plugs tonight and see how the car runs. I also need to re-flash my eManage since for some reason or another I cannot put in negative numbers on my fuel map scale so I have no ability to add fuel under vaccume which I need to do to keep it from running like an a$$
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    JspeXAE102 Well-Known Member

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    simple solution = ignition amplifier
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    Barnacules 100101101011011

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    How do you use an ignition amplifer when you have coil packs?

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