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+--- Thread: Pressurized fuel tank (/showthread.php?tid=2433)
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Pressurized fuel tank - Scarlet O'Hara - 21-02-2019
Been making up an air pump to pressurize a fuel tank and was wondering if Ulsters fitted with such a fuel system incorporate a pressure relief valve or does the driver just rely on watching the pressure gauge while pumping, my engineering instincts say I should fit a blow off.
This prompts the second question - what pressure to set it at, something low, 2 or 3 Lbs/Sq inch?
RE: Pressurized fuel tank - Erich - 21-02-2019
I'm not too familiar with this, but did consider putting one on my Ulster Rep when it had a side draft SU on it. I then converted to a 30 MOV and gravity feed. The original Enots pump had three settings. Off(locked) On(pump) and bleed. The latter was important as on a hot day, you don't want too much pressure. Modern reproductions only have the Off and On settings, so you have to incorporate a bleed valve somewhere. Genuine blown Ulsters had a gauge and I think the pressure was 1-2 lbs/sq inch.Robert Foreman will know much more, and I think was working on a three way pump a year or so ago. Others may also be able to help.
Erich in Seattle
RE: Pressurized fuel tank - Greig Smith - 21-02-2019
I run a pressurized tank in the supercharged single seater, I had to install a one way valve in the line to ensure that the tank remained under pressure as it was bleeding back through the pump.
2 to 3lbs is more than sufficient, if you pump it up too hard it'll just overcome the needle and seat an you will flood the carb.
One or two pumps down the main straight is enough to get all the way round the track even with the blower feeding the oily bits. You will need a tank cap that seals tightly.
Aye
Greig
RE: Pressurized fuel tank - Tom the Blacksmith - 21-02-2019
My 1906 car runs with a pressurised tank, as Greig says at cap that seals well is essential. I called in a favour with a mate who has a flow rig for (old) aircraft carbs to check what pressure my 1st gen zenith works at, 1psi in my case. Once pumped up, it only requires a half pump every now and then to maintain pressure. There's a tap to release pressure when you stop, otherwise it gets a bit incontinent
.Tom
RE: Pressurized fuel tank - Robert Foreman - 21-02-2019
Hello Scarlet,
the original blown Ulster used an Enots air pump as Erich described. It was marked On, Off and Release. You only need 1p.s.i. pressure on the gauge and as the engine warms will need to be able to release pressure from the tank.
Also parked on a hot day unless the valve is set to release you may find quite a pressurised tank when you return.
RE: Pressurized fuel tank - Scarlet O'Hara - 22-02-2019
Thanks for all that and this morning I've made a couple changes.
If my math(s) is right, pressurizing the tank to 1 psi effectively increases the head by about 26 inches which I'm sure is plenty. Incidentally while trying it out yesterday, with the petrol tap open I pressurized the tank up to 5 psi which confirmed the filler cap was sealing but the carb needle valve had still not cracked open which was one reason for thinking about a relief valve.
Anyway I've now incorporated an adjustable relief on the tank connection which I'll set at about 1.5 psi and included a bleed screw on the cap so that I can release the pressure at the same time as turning the petrol tap off.
RE: Pressurized fuel tank - Greig Smith - 22-02-2019
That's a very nice looking pump & tank cap !!
My pump is a modified bicycle floor pump, you can just see it inside the cockpit behind the hand brake lever. The one way valve is inside the bodywork alongside my right hip in the flexible line up to the tank. we have an old compressor gauge which shows low PSI so perfect for this application, it's in the dash just above the pump. When Beloved's surgery upgraded the X-ray machine, I moved it out of the building and into the temporary store for de-comissioning... I did however shamelessly pinch the 3 Bakelite ball handles off the various arms and these became the gear knob, brake lever knob and fuel pump knob - about the same size as the standard A7 gear knob... job done !
I've gotten used to unscrewing the tank cap on the single seater as I get out of it & I can reach over the top of my head to check if it's tight when I'm on the move.
Aye
Greig
RE: Pressurized fuel tank - Robert Foreman - 22-02-2019
Scarlet,
like the pump set up Did you make the pressure relief valve?
If fitting a bronze Solex you will need to change the needle valve when going from gravity to a pressurised system.
RE: Pressurized fuel tank - Scarlet O'Hara - 23-02-2019
Hi Robert, the relief is a modified Norgren minature PRV, which I just happened to have, grafted onto the tank connection. It's a very simple design so I'm sure it could be copied if you've got access to a lathe. Fitted the pump and all the pipework onto the car this afternoon but need to tweek some of the springs and cure a few leaking joints but all looking good so far.
RE: Pressurized fuel tank - Greig Smith - 24-02-2019
Ahh an LAP overhead valve conversion..... Nice
Can you post a better pic of the red C shaped info plate, ours doesn't have this
More pictures of the car too please
Aye
Greig