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Thread: Gas mileage terrible on new Sniper install.

  1. #21


    Certainly, your transmission problems could lower gas mileage. Your "knowledgeable" transmission person could drain your money.

  2. #22


    Quote Originally Posted by XW_Falcon_351C View Post
    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 converter 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.
    Hi Falcon. The Quad carb that I had was the Q-Jet, the electronic version. This carb has modules that connect to the ECM, such as TPI, Metering rods, and others that I am not that familiar with. The ECM takes constant readings from the carb and will then adjust fuel/air, and will control the converter lock up when needed. I really don't know how it works. Everyone that I know that has eliminated the computer have the same problem. No lock up with the converter and no cruise control. For some reason the ECM controlled the ground for the cruise, this will be an easy fix. Louis

    UPDATE: Hello again. I must apologize to Holley and this board for thinking the Sniper was causing my fuel problems. I removed the spark plugs and they look like a model plug, tan and not covered with soot. My problem is the converter lockup on the transmission that's slipping badly. This was caused by the disconnect of the car's ECM. I have a converter coming to convert the transmission to have the lockup controlled by outside means. I'm sure this will solve the fuel problem. Details at 11. Louis

  3. #23

    Wink Fuel Problem Update

    Happy to say that the fuel problem has been solved. I installed a kit to activate the converter lockup automatically. It's made by Bowler transmissions. Real simple install. I filled the tank and put a measly 50 miles on it and I'm getting around the same mileage I did with the QuadraJet carb. Around 14+ MPG. Filled the tank again and I'll recheck the mileage with a couple hundred miles. Sniper is running great (knock on wood). Louis

  4. #24


    Firstly, congrats for finding that issue!

    Second, with a relatively light car, a locking torque converter and a relatively small engine, you should be able to get better mileage numbers. Get the Sniper EFI software and start tuning, there's gains to be had.

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