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Thread: Spark blowing out on dyno?

  1. #1

    Default Spark blowing out on dyno?

    My car hit the rollers today and we started running into problems as boost increased. At low boost (5-10 psi), power was increasing 35-40 HP per pound of boost. After that it started dropping off to the point of only gaining 10-15 HP per psi. After one of the pulls I regapped the plugs from .026" to .022" and picked up 120 HP! I'm running a 427 LSx twin Borg S400SXEs 76/82 on E85 with stock LS1 coils. Am I having weak coil issues?

  2. #2

    Default

    What fuel are you running?

  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,113

    Default

    He stated E85.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  4. #4

    Default

    Having plugs gapped to .022" is not uncommon. You've got to keep it lit. Have you reached your target boost?

  5. #5

    Default

    Not uncommon with Holley EFI & boost. To threads out there with people having the same issue. Seems Holley EFI is finicky driving the OE coils. You may need to go tighter than .022", but that's where I'm at. Suggestion - pull a an extra ground wire to the coils, it's crucial.
    96 MUSTANG/6.0 LQ9/S475 T4/HOLLEY HP EFI/TH400/3.27

  6. #6

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    I have a ProCharged SBF @ 18 psi. Boost will blow the flame out. Tight gaps are usually necessary.

  7. #7

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    Interesting thread. My car will be hitting the rollers on Holley EFI for the first time in about a week or two. Hope I don't have this issue. But at least I will know what a possible/solution is. Vince, when you say add an extra ground, where would you send this ground to? I was under the impression that the coils grounded through the harness, and then to that ground wire that usually goes on the back of the head?

  8. #8
    Join Date
    Nov 2013
    Location
    Chicago IL
    Posts
    1,952

    Default

    Key things important to keep the plugs lit under Boost.

    1: GOOD GROUNDS
    Meaning grounds from the engine directly to the battery, not using your frame as a ground for anything EFI, coils grounded to the Cylinder Heads.

    2: Good Coils & Wires
    Certain coils don't work well. Stick to newer LS3 Coils (2010 Camaro or Corvette coils) or use Holley/IGN1A coils.
    If you are using a CD Ignition Based system, Use the HVC2 coil or a Jacobs Blue Coil, not a small wimpy "MSD Street Fire" coil.
    Don't use Autozone cheap generic wires. Stick to MSD, FireCore50, Accel, Taylor, and other major racing name brands.

    3: Plugs & Gap
    Most of the time you will need a pretty tight gap for boost.
    The more boost, (and more initial engine compression) the tighter the gap.
    At 20 PSI, on 11.5:1, running C16, I'm at a gap of .015".
    Run a good Copper Plug, NGK BR7EFS is a good example.
    On boosted engines, you need a plug that is a Non-Protruding tip and a Solid tip.
    No Split Fire, no three electrode crap, no Iridium, standard Copper Plugs.
    Proper Heat Range is important too. A LOT of people go too cold. If you can't read a plug, you shouldn't be trying to put a bunch of power to it.
    Again, my setup, 20 psi, 11.5:1 compression, C16, NGK BR7EFS (yes, that's a heat range 7), it doesn't need to be colder than that if you are less boost & less compression.
    My buddy's car, 5.3L LS1, 10:1 compression E85, also an NGK BR7EFS, it doesn't need a colder for his setup.

    On LS1 setups, the coils like to have a Resistor Plug (the R in BR7EFS).
    If you can't get a resistor plug in the spark plugs you like, then consider buying a resistor boot for your plugs (it adds the resistance in the plug boot itself).
    -Scott
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  9. #9

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    I'm installing the Holley coils, what should I gap my plugs to? Also, I'm trying to adjust my Dwell and it's blacked out and won't let me select it. Any idea why?

  10. #10
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,113

    Default

    Quote Originally Posted by Lmt0705 View Post
    Also, I'm trying to adjust my Dwell and it's blacked out and won't let me select it. Any idea why?
    You need to "Enable Dwell Table" in Ignition Parameters/Configure/Output Setup.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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