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Thread: extra fuel tank

  1. #1
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    extra fuel tank

    Hi everyone,
    so while I have been laid up resting with my leg elevated I have had too much time on my hands, I have been thinking about extra fuel capacity in my P38. I don't like LPG and it is not that cheap in Queensland anyway. My spare won't fit in the space below the floor, so I am looking at making a rear bar with one or two spare wheels mounted on it. So what to do with the spare wheel space. Then I thought if I cut it out and welded in a flat plate I could then mount an extra fuel tank under the floor. An electric fuel pump could pump the fuel from the reserve tank into the main tank once the main tank got down low enough. I would need to put an extra fuel filler some where, and add in a extra fuel gauge, and pump. See I told you I had too much time on my hands.
    Regards,
    Alan

  2. #2
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    extra fuel tank

    Well a lot of people have read this thread but no one has commented. I am not sure if everyone is still in shock that I would cut the bottom out of my Range Rover. Or that it such a stupid idea that it was not worth commenting on.
    Alan

  3. #3
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    I once thought about it to fit a larger LPG tank. I also wondered if, after cutting the floor out, I could drop a 10 gallon (45 litre) Hillman Hunter tank in there. The Hunter tank is flat on top, bolts in from the top, and forms the boot floor.

    Hillman-Hunter-Fuel-Tank.jpg
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  4. #4
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    extra fuel tank

    Hi p38arover, I thought there would be other people who had similar ideas as me. That is a good idea but Hillman fuel tanks are a bit thin onthe ground around here. I thought of making my own tank that way I could put the filler, pickup etc. where I would want it to be.
    Thanks for the reply,
    Alan

  5. #5
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    Mate,

    I have a similar setup planned. Although I am not going to cut out the spare wheel well, I am just going to drop in a custom made fuel tank. I reckon I can make it out of thinner and lighter material (aluminium for example) since it does not to be so heavily protected, the spare wheel well itself takes care of that.

    I measured it roughly and I reckon I could fit an extra 120L in there which would be nice! I am considering modifying the fuel filler so that I move it over a bit, and on an angle, so that I can fit 2 filler pipes and caps behind one (factory) door.

    It's all still in the planning phase though since the one thing I run into with my P38 is weight. 120L of fuel, with an ali tank and needed gear would weigh 120kg at least and the P38 is not known for it's large carrying capacity. Even when trimming down a lot on gear and such I would still be consistently overweight though in case of fuel/water I tend to look the other way since they run out rather quick, certainly in a P38 running on petrol

    Cheers,
    -P

  6. #6
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    extra fuel tan

    Hi P, yes I had thought of just making a tank to fit in the spare wheel hole. But to be ADR compliant I believe the tank would need to be sealed in place. I also was thinking of making my tank out of alloy. I made a new one out of alloy for my boat a while back. It holds 480 liters. A lot of hours on the TIG welder. And if you could fit both fillers in the one filler door that would make the installation a lot easier. I have several P38's but the one that is my regular driver returns about 10 lts. per 100 klm. on the open road, driving sensibly (105kph). Which I don't think is too bad.
    Regards,
    Alan

  7. #7
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    10 lts. per 100, it has been a while since I have seen that With all the mods, stage 3 engine, etc. I am lucky to get 16 per. Certainly when I start driving dirt tracks or sand even I need more fuel for sure. I guess to be compliant I need to cover the fuel tank up indeed but I figured that to be preferable to hanging it underneath.

    Thinking about it... Weight IS an issue and the weight of the spare wheel well plus a cover on the inside will also add up. Gah! sometimes I think the P38 is just not able to carry enoguh weight

    Cheers,
    -P

  8. #8
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    : extra fuel tank

    Hi Prelude,
    when you say you are using a lot more fuel, what sort of mileage cruising on the highway do you think your vehicle would average? Is yours a Gems or a Thor? And what computer (ECU) are you running? I have a 1995 P38 I have been working on for a while, motor mods etc. but I have not had it on the road yet. I was hoping to get better fuel consumption figures that standard as the original ECU tune was crap, on an engine with less compression than a FC Holden.
    Regards,
    Alan


    Quote Originally Posted by prelude View Post
    10 lts. per 100, it has been a while since I have seen that With all the mods, stage 3 engine, etc. I am lucky to get 16 per. Certainly when I start driving dirt tracks or sand even I need more fuel for sure. I guess to be compliant I need to cover the fuel tank up indeed but I figured that to be preferable to hanging it underneath.

    Thinking about it... Weight IS an issue and the weight of the spare wheel well plus a cover on the inside will also add up. Gah! sometimes I think the P38 is just not able to carry enoguh weight

    Cheers,
    -P

  9. #9
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    Alan,

    I have a 1998 Gems 4.6 (the very last of them). The engine has been completely rebuild to "stage 3" spec. This means ported and polished heads, also the air intakes have been enlarged to suit, top hat liners, a piper 285 camshaft and all new internals. I also have a tornado chip in the ECU to help that crap tune

    The thing is, I never had just the engine done, at the same time I got HD axles, lockers, double cardan drive shafts, etc. so the entire driveline got quite heavy.

    In any case, fully laden on a long trip with the RTT on top I get around 16.8 per 100. It does not really seem to matter what the outside temp is. I've done a trip to the north cape in winter (getting temps far below -20c) with admittedly thinner oil and a near stock tyre size, and I have done trips around summer in europe with 20w50 oil and 32" mud tyres and done about the same when accounting for the 10% difference in dash readings. When I switch back to the stock tyre size, which I do about once a year for the MOT the dash gives me much better mileage but I have never seen the car go lower than 12l per 100 when bone stock at 80kph on a straight and level highway.

    What I have noticed is that the car really get's "very" economical if I keep the speed between 100-120kph. Weirdly enough driving about 80 is not more economical. I guess that has got to do with the gearing, the powerband of the engine and the ECU tune of the tornado chip. Perhaps, some day I will get myself a megasquirt and really get into it.

    Cheers,
    -P

  10. #10
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    : extra fuel tank

    Hi Prelude,
    my motor is about the same as yours but I have fitted Hurricane headers and I got rid of the cats and fitted a straight through muffler and 3inch system from the Y join back, and 60mm pipes from the headers to the Y join. The big thing that holds the 4.6 back is it can't get rid of the exhaust gasses quick enough. The people that make the aftermarket cylinder heads have overcome the problem by making their heads about 1/2 an inch higher, a lot more port area. Also they moved their valves to the middle of the cylinders which allowed them to fit much larger valves.
    The after market head people, I can't remember their name right now, dropped the price of their heads just after I had spent 2 months porting, polishing, triple cutting the valves and seats, checking and adjusting combustion chamber and port volumes and setting the seat pressures. At the new price I would had gladly paid the money for their heads. I also have a tornado chip fitted to my ECU. I am hoping to get a bit better fuel economy out of the 95 P38. I haven't done anything to the drive line yet, but I I do have a MaxiDrive locker rear end to fit in it soon. Yes I think that your camshaft would be starting to make good torque at just over 2,000 rpm. Which with 32'' tires you would need to be well over 80 kph. I think 120 kph it would be just in the bottom of the power band, 2 stroke terminology. Are you located in England? (MOT), none of that over here in Queensland Australia. I am trying to have my -/95 P38 going by the end of next week, so it won't be long and I will see how much fuel it uses and how well it goes on the road..
    Regards,
    Alan Temperley


    Quote Originally Posted by prelude View Post
    Alan,

    I have a 1998 Gems 4.6 (the very last of them). The engine has been completely rebuild to "stage 3" spec. This means ported and polished heads, also the air intakes have been enlarged to suit, top hat liners, a piper 285 camshaft and all new internals. I also have a tornado chip in the ECU to help that crap tune

    The thing is, I never had just the engine done, at the same time I got HD axles, lockers, double cardan drive shafts, etc. so the entire driveline got quite heavy.

    In any case, fully laden on a long trip with the RTT on top I get around 16.8 per 100. It does not really seem to matter what the outside temp is. I've done a trip to the north cape in winter (getting temps far below -20c) with admittedly thinner oil and a near stock tyre size, and I have done trips around summer in europe with 20w50 oil and 32" mud tyres and done about the same when accounting for the 10% difference in dash readings. When I switch back to the stock tyre size, which I do about once a year for the MOT the dash gives me much better mileage but I have never seen the car go lower than 12l per 100 when bone stock at 80kph on a straight and level highway.

    What I have noticed is that the car really get's "very" economical if I keep the speed between 100-120kph. Weirdly enough driving about 80 is not more economical. I guess that has got to do with the gearing, the powerband of the engine and the ECU tune of the tornado chip. Perhaps, some day I will get myself a megasquirt and really get into it.

    Cheers,
    -P

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