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Thread: Cooling fuel Tank

  1. #1
    Senior Member Bitsyncmaster's Avatar
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    Cooling fuel Tank

    I've thought about doing a circuit to power the fuel pump that would reduce the return fuel to the tank. This was a major thing running the original type fuel pump because it would buzz when the gas in the tank got hot. Now with the new type pumps this does not seem to be a problem. But would there be any other advantage to cooling the fuel in the tank?

    Most all injected cars use a return line to control fuel pressure. Their pressure regulator is not mounted on a hot engine though.

    To control our fuel pump I would have a pressure sensor to reduce electrical power to the pump above 75 PSI. I would probably keep the existing PPR but add a shim to set that around 80 PSI.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #2
    '82 T3 FABombjoy's Avatar
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    Modern pumps can cavitate just like originals, seems like you're just less likely to hear it. I got one of the new pumps to cavitate with a few too many 90-degree fittings. Added tank insulation and re-plumbed a few lines and it quieted down when hot. It's probably more likely to surface at EFI pressure.

    If there's room with K-jet to PWM the pump speed down it would be a worthwhile upgrade as part of a multi-headed strategy. I have an FPDM here that I plan to use during the next stage of my car, you could definitely accelerate development by incorporating a similar OEM pump controller. Then if an owner converts to EFI later the work is already done, they'd just wire the PWM input to their ECU and be up and running.

    My first thought with using fuel pressure as an input is that by the time fuel pressure drops and you increase pump d/c, you have to refill the accumulator at the same time and the system could swing lean briefly. A MAP input might be needed to iron out transient conditions? Maybe not if it dips just enough under load to be detected before the accumulator is empty.

    If only there was a way to measure accumulator diaphragm position because that would be the ideal control input for a PWM driven pump on a K-jet car.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

  3. #3
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by FABombjoy View Post
    Modern pumps can cavitate just like originals, seems like you're just less likely to hear it. I got one of the new pumps to cavitate with a few too many 90-degree fittings. Added tank insulation and re-plumbed a few lines and it quieted down when hot. It's probably more likely to surface at EFI pressure.

    If there's room with K-jet to PWM the pump speed down it would be a worthwhile upgrade as part of a multi-headed strategy. I have an FPDM here that I plan to use during the next stage of my car, you could definitely accelerate development by incorporating a similar OEM pump controller. Then if an owner converts to EFI later the work is already done, they'd just wire the PWM input to their ECU and be up and running.

    My first thought with using fuel pressure as an input is that by the time fuel pressure drops and you increase pump d/c, you have to refill the accumulator at the same time and the system could swing lean briefly. A MAP input might be needed to iron out transient conditions? Maybe not if it dips just enough under load to be detected before the accumulator is empty.

    If only there was a way to measure accumulator diaphragm position because that would be the ideal control input for a PWM driven pump on a K-jet car.
    Good points you have made. I'm thinking the accumulator is maxed out before the pressure hits the 75 PSI primary pressure.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #4
    Senior Member Bitsyncmaster's Avatar
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    If I had another accumulator I would test it's capacity at some pressures.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #5
    Senior Member r00b's Avatar
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    There are lots of different kinds of fuel coolers already on the market. While doing my frame swap, I was looking for one. I did consider using the stainless frame as a heat sink. After insulating the coolant pipes around the tank and going with a new style pump I never had a problem again so didn't end up getting one of those coolers.

    fuel0.jpgfuel2.jpgfuel1.jpg

  6. #6
    Senior Member Bitsyncmaster's Avatar
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    I did a cooler already which did cure the buzzing problem. Look at post #3 in this thread.

    https://dmctalk.org/showthread.php?1...=return+cooler

    Now I'm just wondering if cooler fuel tank gas has any other advantage.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #7
    Senior Member r00b's Avatar
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    I don't know if there is any thing conclusive about using cold fuel, maybe you could have a coiled fuel line go through an ice chest just to test things out and see what happens with cold fuel.

  8. #8
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    Quote Originally Posted by r00b View Post
    I don't know if there is any thing conclusive about using cold fuel, maybe you could have a coiled fuel line go through an ice chest just to test things out and see what happens with cold fuel.
    Cold fuel is more difficult to vaporize and ignite. Putting a chiller in the loop is for alcohol racing. You don't want the alcohol vaporizing before it hits the engine.
    Any one that lives were it can get really cold can tell the difference just having the car in a garage without heat.

    This is the reason fuel return lines were invented. On old carb cars without fuel return lines had a tendency to Vaporl ock in the fuel pump



    Dave B

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