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  1. #1
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    Default Pajero Gen4 SWB fuel tank

    Hi All

    The Achilles heel of my Gen4 SWB Pajero 3.8 V6 seems to be range. The fuel consumption is acceptable for a 2t+ V6 4x4 at an avg. 7.2km combined giving me a safe range (69l -5l= 64l) of around 460km. This is just not feasible when travelling overland and is a real annoyance on longer road trips.


    I have started to design a very basic extra fuel tank that should give me another 60l, the tank is a dumbed down version of the aux fuel tanks offered in AUS. The aux tank should push the range to over 800km while cruising which I consider usable range. The tank will be made from aluminum and have a transfer pump from the sub to main tank. The exhaust will also need to be diverted and the main silencer replaced with a smaller unit to make room for the tank.


    The transfer and refuel is where I am getting stuck. Firstly filling both tanks from one filler nozzle, to keep things simple I am thinking a y-piece from the main filler to both tanks. My thinking is that the y-piece will also act as a safety buffer for overfilling the main tank using the transfer pump as the fuel will simply return to the aux tank via the y-piece. Obviously a separate breather will be needed for the aux tank. Will a Y-piece work?

    Then there is the transfer pump itself, I would prefer to use a simple exterior inline pump that can be replaced with any basic pump bought from an auto parts store when the need arises. If this method is followed I assume I would need a small sump to get as much of the fuel out as possible. A basic in-line fuel filter will also be added. I would also need a early warning system to stop the pump from running dry, for this I was thinking a pressure switch with a alarm that activates as soon as the pump is switched on and the pressure drops below a set value. Any suggestions to prevent the pump running dry would be appreciated. I'm not interested in knowing the level of the aux tank rather just stopping the pump once its empty.

    Would the tank require baffles and if so how many?

    Attached is my first draft of the main tank body.
    Attached Files Attached Files
    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

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  3. #2
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    Default Re: Pajero Gen4 SWB fuel tank

    Please note none of the above dimensions are final, and everything still needs to be modeled.

    The attached should give a better idea of how the tank should end up.

    Also toying with the idea of a dual filler neck instead of a y-piece. If I do use a y-piece it would be just after the bend at pipe no. 28.
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    Last edited by pjf110; 2021/05/11 at 03:47 PM.
    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

  4. #3
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    Default Re: Pajero Gen4 SWB fuel tank

    I like the idea of the dual filler neck, Toyota has a nice filler neck for dual tanks.
    Will have a look if I can get a part number for you.

    I did a quick model on your dimensions and end up at 66L.

  5. #4
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    Default Re: Pajero Gen4 SWB fuel tank

    Quote Originally Posted by Takashi View Post
    I like the idea of the dual filler neck, Toyota has a nice filler neck for dual tanks.
    Will have a look if I can get a part number for you.

    I did a quick model on your dimensions and end up at 66L.
    Jip its a 80 series OEM duel fuel filler neck, just way too bulky.

    I used 60l as a conservative figure in case the dimensions need to change or the pump struggles to get the last few liters of fuel.
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    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

  6. #5
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    Default Re: Pajero Gen4 SWB fuel tank

    Well I hope you dont plan to do any serious off road , I broke my rear bumper off and it looks like the alum tank is lower so will hit rocks etc
    Pajero 3.2 DID Gen 4 Standard for now
    Platcar Alfa Giulietta 1.4 MA
    Swambo Volvo S40 T5

  7. #6
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    Default Re: Pajero Gen4 SWB fuel tank

    Quote Originally Posted by 12richardk View Post
    Well I hope you dont plan to do any serious off road , I broke my rear bumper off and it looks like the alum tank is lower so will hit rocks etc
    This is definitely a concern but the SWB has a short overhang and I plan on installing a small lift to mitigate tank damage. A fuel tank bash plate may be considered in the future.
    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

  8. #7
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    Default Re: Pajero Gen4 SWB fuel tank

    So a few updates:

    Removed rear muffler and built a model to see how far my measurements were off.
    End result is 2cm off the top and 5cm longer, still over 60l.

    The tank sits close to inline with the rear diff, hence the 2cm reduction to move the tank up slightly.
    I've also added a baffle to the design, not sure how effective it will be.
    Mounting tabs will need to be retrofitted as I'm sure the manufactured product and my crude model will differ slightly.
    This will also be the case for the tank breathers.

    Attached new design and some photos of the mock up.
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    Attached Files Attached Files
    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

  9. #8
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    Default Re: Pajero Gen4 SWB fuel tank

    I would appreciate some advice regarding the ventilation system of the Aux tank, I much prefer the aux tank to have its own breather than to piggy back from the main tank.

    Is it a simple case of taking a vent tube with a breather valve to a higher location than top of tank or would I need a vent pipe and vapor return hose as in two of the below examples?
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    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

  10. #9
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    Default Re: Pajero Gen4 SWB fuel tank

    Quote Originally Posted by pjf110 View Post
    i would appreciate some advice regarding the ventilation system of the aux tank, i much prefer the aux tank to have its own breather than to piggy back from the main tank.

    Is it a simple case of taking a vent tube with a breather valve to a higher location than top of tank or would i need a vent pipe and vapor return hose as in two of the below examples?
    bump
    Pieter Greyling
    Of all the paths you take in life make sure a few of them are dirt-John Muir
    ORRA: Z85

    -Pajero SWB 3.8 V6
    -BMW F800GS

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