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Thread: Gas mileage terrible on new Sniper install.

  1. #11
    Join Date
    Dec 2009
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    Connecticut
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    22,132

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    The "Fuel Flow" channel is LBS/HR.
    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.

  2. #12
    Join Date
    Oct 2016
    Location
    Albuquerque, NM
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    95

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    From what I read, let it settle for about a minute after each change. You can adjust both idle & cruise for MPG and WOT for power.

  3. #13

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    Quote Originally Posted by Firebird View Post
    Hi everyone. I have a new Sniper install in my 1987 Firebird 305 engine. Runs great, I used Chris' method of setting the idle and it worked great. I've only put about 80 miles on the unit. Decided to check mileage with a top off using the Sunoco ethanol free 93 octane. I had originally had a QuadraJet carb that I got only 14 MPG. However, checking the mileage now, I'm getting only 9 MPG. My eyes glaze over when I look at the Sniper software. Can something be done about this? It does smell rich. I pulled a couple of plugs and they appear to be normal, maybe just a tad black. Any ideas you can give me would be appreciated. Louis
    You did something wrong. The mileage on my car increased significantly once I installed the Sniper & HyperSpark. You should be able to figure it out if you watch your datalogs and pay attention to what the EFI system is doing.

  4. #14

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    Thank you js5d for your input. I have a little update. When I removed the carb and installed the Sniper, this made the car's ECU useless. I've lost the cruise control, on my bucket list, and the other is that my converter lockup no longer works. I talked to a knowledgeable (?) transmission person and he said that for all practical reasons, I don't need it. However, I now find that without the lockup the mileage will suffer greatly. So for the time being, I'll put this project aside until I can get a lockup kit installed and then see what the mileage will be. I'll let you know the results. Thanks all for all your input. Louis

  5. #15

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    They make modules to control lockup. I'm guessing 700R4? I know TCI makes one.

  6. #16

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    Uh yeah, disconnecting the lockup will cause some problems. You didn't mention that fact in your first post.

  7. Default

    Can you expand on how changing from a QuadraJet Carburetor to Sniper made your cars ECU useless, the loss of cruise control and convertor lockup no longer working?
    How was the QuadraJet Carb previously connected to work with these items?
    If a vacuum activated switch was used previously to trigger the TCC, then this should continue to work now providing convertor lockup. External cruise control actuators could still be used with Sniper providing the external cruise control controller performs speed sensing, brake pedal sensing to deactivate and modulating the actuator to maintain speed. Providing the vehicles existing cruise control module was modular enough it could be possible to continue to use it.

    Alternatively if you have 2x spare Sniper outputs you can get creative and control your TCC similar to how EFI V5 TCC functionality works.
    Use the Secondary Fuel Pump output options to perform the 'Unlock' action. Define WOT TPS value to unlock, define WOT MAP value to unlock.
    Use Nitrous output stage to perform the 'Lock' action. Define minimum TPS for lockup, define minimum RPM for lockup.
    Last edited by XW_Falcon_351C; 08-13-2019 at 04:31 AM.
    1970 XW Fairmont (presented as a GT Falcon Replica), 351 Cleveland with Aussie 302 2V closed chamber heads. Edelbrock F351 2V dual plane intake manifold. Camtech CT21544 (234/238@050", 570/579lift, 2600-6200rpm quoted range, 110lobes) 1.73:1 roller rockers. AOD Transmission. Ford 9" 3.5 Diff ratio. Pacemaker #PH4050 2v Tri-Y extractors to 2.5" Hi Flow V-Tex merge pipe with dual 2.5" exhaust through Hooker Aero Chamber Mufflers. Holley Sniper EFI 4150 Super Sniper 650 with HyperSpark Ignition.

  8. #18

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    I believe those cars had a second linkage from the actuator to the throttle bracket. The only other electronic connection was for the metering rod thing on the carb. The transmission contoler was behind the dashboard. I don't remember if there was a vacuum line that ran to it.

  9. #19

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    Quote Originally Posted by XW_Falcon_351C View Post
    Alternatively if you have 2x spare Sniper outputs you can get creative and control your TCC similar to how EFI V5 TCC functionality works.
    Use the Secondary Fuel Pump output options to perform the 'Unlock' action. Define WOT TPS value to unlock, define WOT MAP value to unlock.
    Use Nitrous output stage to perform the 'Lock' action. Define minimum TPS for lockup, define minimum RPM for lockup.
    Glad to see validation on the concept I came up with to handle my TCC lock when I buy/install my Sniper later this year. :-)

    The fun part is the 5 second min enable time for the Secondary Fuel Pump that disables TCC forces at least 5 seconds with TCC off if you hit the throttle/MAP thresholds tied to the Secondary Fuel Pump 'enable'. Not sure that's a big problem, but I'd love to be able to shorten that time a little (say 2 seconds or so instead of 5 seconds).

    Of note, if the OP has a 700R4, many of those have a 4th gear switch that grounds to enable TCC only when in 4th. Using this as the enable for the 'Nitrous Stage' would also keep TCC from trying to apply in lower gears. Of course, some want TCC in lower gears, so this is not valuable, but figured I'd mention it.

  10. Default

    Not sure if the 'Nitrous Stage' has a hysteresis on the minimum RPM to activate. It wouldn't be desirable for Nitrous, but when using the Nitrous function block to perform TCC enable, I can see an edge case when RPM is near the activation area that might cause undesirable affects. E.G. minimum activation point at 2200 RPM. Engine RPM increases to 2200 and activates. Lockup lowers RPM slightly to 2000 RPM for example. Below the trigger setpoint causing it to deactivate. RPM increases above, activates, deactivate, activate, etc. It should work OK once the lockup RPM is sustained higher then the minimum RPM to activate. Possibly adding Nitrous Stage Activation Delay of a few seconds to allow RPM to stabilize a few hundred RPM above the minimum RPM to activate would help reduce this occurrence.
    1970 XW Fairmont (presented as a GT Falcon Replica), 351 Cleveland with Aussie 302 2V closed chamber heads. Edelbrock F351 2V dual plane intake manifold. Camtech CT21544 (234/238@050", 570/579lift, 2600-6200rpm quoted range, 110lobes) 1.73:1 roller rockers. AOD Transmission. Ford 9" 3.5 Diff ratio. Pacemaker #PH4050 2v Tri-Y extractors to 2.5" Hi Flow V-Tex merge pipe with dual 2.5" exhaust through Hooker Aero Chamber Mufflers. Holley Sniper EFI 4150 Super Sniper 650 with HyperSpark Ignition.

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