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Fuel System Design

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  • ahk068
    replied
    Originally posted by Komdotkom View Post
    You have got a lift pump with decent capacity running at very low pressure, so assuming you are supplying good voltage to it you have a shit load of fuel (255 is rated at 302L at zero pressure) going in circles between the tank and the surge tank. Your lift pump only needs to supply as much fuel as your engine can burn, I would suggest that with a 255 as a lift pump you always have a 100% full surge tank so the return line from the surge to the tank is dealing with essentially 2x the volume of fuel.
    I think.youre close to the mark. The 255 ran the car ok at 250rwkw. I just used to get starvation at less that half a tank which Is why the surge tank was installed. Now I'm at 350rwkw and e85 I don't think it would keep up at higher revs.

    Staging the fuel pumps is another option to keep system pressure low at idle.

    Leave a comment:


  • ahk068
    replied
    Originally posted by BLO 767 View Post
    You haven't mentioned any breathing... is it actually vented, anywhere? If not, I'd say you've found your reason why you're splitting surge tanks.
    factory venting set up. main tank isn't pressurised

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  • Komdotkom
    replied
    You have got a lift pump with decent capacity running at very low pressure, so assuming you are supplying good voltage to it you have a shit load of fuel (255 is rated at 302L at zero pressure) going in circles between the tank and the surge tank. Your lift pump only needs to supply as much fuel as your engine can burn, I would suggest that with a 255 as a lift pump you always have a 100% full surge tank so the return line from the surge to the tank is dealing with essentially 2x the volume of fuel.

    Leave a comment:


  • BLO 767
    replied
    You haven't mentioned any breathing... is it actually vented, anywhere? If not, I'd say you've found your reason why you're splitting surge tanks.

    Leave a comment:


  • TROLLA
    replied
    Generally a bad idea unless you have some mega lift pumps.

    Leave a comment:


  • slipway
    replied
    Can you not just re route return to main tank and leave surge tank return in place to relieve pressure if it continues.

    Leave a comment:


  • ahk068
    replied
    The more I ponder the more I think something funky is going on.

    The car still runs the purge solenoid and charcoal cannister so first job is to remove all that.

    I'll replace surge with same tank but remove the factory return line for a bigger one. I'll also plump this to the top of the fuel tank rather than into the 'pot' because that has to be causing some resistance/pressure because the pots generally always covered in fuel. Roll-over vents will have to go in too

    Leave a comment:


  • greenhj
    replied
    Originally posted by ahk068 View Post
    The falcon pressurised the surge tank and split it on Sunday so need to make some changes (don't know why but it's happened twice). Current set-up is factory tank with walbro 255 in factory cradle feeding surge tank and a single 044. Reg is between fuel rail and surge tank on return side. Return line runs from surge to factory tank.

    Option 1
    Twin pump hanger in tank with hydromat and no surge tanks. Makes plumbing easier and will have plenty of pressure.

    Option 2
    Underfloor surge tank, similar configuration to what I have but feed the return line straight to main tank from reg.

    Option 3
    Suggestions?
    Fit a pressure reg at the correct setpoint on the surge tank to blow down when its overpressured?

    Leave a comment:


  • TROLLA
    replied
    There is nothing wrong with current, a few pressure sensors would sort it but your return line from surge to tank is too small unless you have some weird shit going on with carbon canister and pressurising tank with boost.

    Leave a comment:


  • ahk068
    started a topic Fuel System Design

    Fuel System Design

    The falcon pressurised the surge tank and split it on Sunday so need to make some changes (don't know why but it's happened twice). Current set-up is factory tank with walbro 255 in factory cradle feeding surge tank and a single 044. Reg is between fuel rail and surge tank on return side. Return line runs from surge to factory tank.

    Option 1
    Twin pump hanger in tank with hydromat and no surge tanks. Makes plumbing easier and will have plenty of pressure.

    Option 2
    Underfloor surge tank, similar configuration to what I have but feed the return line straight to main tank from reg.

    Option 3
    Suggestions?
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