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Thread: Sniper is backfiring.

  1. #1

    Default Sniper is backfiring.

    Hey guys. I have a 383 stroker in a '69 Camaro. Dynatech long tube headers with 3" Dynatech exhaust. I just installed the Sniper with HyperSpark distributor. Car runs so much better, except it backfires of more like pops a ton. Driving me crazy. I assumed it may be exhaust leak.

    I mounted the WBO2 sensor about 2" behind the header collector as per the instructions. I used a Shop-Vac to test for exhaust leaks by pressurizing the exhaust and sprayed soapy water, so I found several small bubbles around the WBO2 clamp on bung and a few just after the header collector. My question is with the exhaust pressurized will those small leaks matter and could that be the source of my backfires? Second question is after the WBO2 sensor about 10", I have a band clamp that leaks a little bit would that be an issue also?

  2. #2

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    What do you mean by backfire? Is it backfiring out the intake, or popping out the exhaust? You might have an ignition timing problem rather than a Sniper problem. When does it backfire? Acceleration or deceleration?

  3. #3

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    It's all exhaust. I read last night after my post, that popping describes out of the intake. It's all exhaust only under load and it's is both acceleration and deceleration, more deceleration or in 4th gear low RPM.

  4. #4

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    Anyone have similar problems?

  5. #5

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    Popping in the exhaust is excess fuel being burned in the exhaust. I had a similar problem that wound up being a worn lifter and cam lobe that kept the exhaust valve open sometimes.

  6. #6

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    I fixed the exhaust leak. I pulled the clamps and welded it, along with a welded bung for the WBO2 sensor. I was unable to get a seal with the clamp-on bung. I called Holley tech line and the guy was good. He said a leak by the WBO2 sensor would cause too much fuel being fed and lead to not all being burnt. Also, my idle timing is at 14°, way too little. With my carb I had 16° & 34° at 3000. So I'll setup the timing to retard it a bit more. I'll update when I figure it out.

  7. #7
    Join Date
    Dec 2009
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    Default

    Quote Originally Posted by Deroid226 View Post
    Also, my idle timing is at 14°, way too little. With my carb I had 16° & 34° at 3000. So I'll setup the timing to retard it a bit more.
    I think you mean advance it from 14° to 16° at idle.

    Originally Posted by Danny Cabral
    The Target Air/Fuel Ratio Table & Base Fuel/Timing Table (and MAP kPa & RPM axes/scales) should be configured using the Sniper EFI software:
    In the Sniper EFI software (LINK), Target Air/Fuel Ratio Table (Fuel ICF) & Base Timing Table (Spark ICF), select "2D Table" Type (not "Simple").
    The Target Air/Fuel Ratio Table & Base Timing Table can then be properly configured & tuned for any engine.
    https://www.holley.com/support/resou...Fuel_Injection (Sniper EFI Software & Holley 558-443 CAN/USB Dongle)
    https://forums.holley.com/showthread...679#post100679 (Sniper EFI Optional Comm/Data Cable Accessories)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, 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.

  8. #8

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    Quote Originally Posted by Deroid226 View Post
    Anyone have similar problems?
    Popping in the exhaust is not a Sniper problem. You have a mechanical issue somewhere. I've installed a lot of Snipers and they don't pop or backfire.

  9. #9
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    21,866

    Default

    I agree it's not a Sniper EFI problem per se, although I suppose it could be a tuning issue.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, 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.

  10. #10

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    I don't think anything is wrong, just not tuned properly. I definetly had a few "pinhole" exhaust leaks infront of WBO2 sensor including the strapon bung. All welded now.
    Now I'll check timing. With carb I had about 17° at idle for best vacuum running, I may need more timing now? It never backfired with my carb. So tune time it is.

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