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So any of you cunts know what you're doing when it comes to fuel systems?
Im currently building an off-road racer, and i'm about at the point where i'm going to have to start making room for the fuel system.
The car has 3 main bits separated by big bulkheads; Fuel Cell up front, Cockpit, and Enginebay out back. The problem is that i'm using an FiTech injection unit, with a bosch 044 pump, so if i build it with the pump in/under the tank i'll have a 5 bar fuel line running through the inside of the cockpit. Not great, and sadly, MSA regs specify the fuel lines have to be inside the vehicle.
So i've come up with the idea of using the mechanical fuel pump on the engine (which gives more than enough flow, and self regulates @7psi), to feed into a small tank by the engine, feeding the HP pump and EFI. Return line feeding back into small tank, with a vent/overflow running back to the main tank.
The main theory for it being that there shouldn't be any pressurised fuel running through the cabin, and any air pulled from the main tank sloshing about shouldn't reach the HP pump.
But i'm new to the world of fuel injection, so let me know if there's anything i may have overlooked or just done stupid. Will the system work?
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Diagram should make it easier.
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aaaand a shot of the engine bay.
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Just use a 1" diameter pipe to isolate the fuel lines as they run through the cockpit
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>>16459662
Looks like it would work but could heat up your fuel. Put a fuel cooler in the loop between after inj unit. Also, where does this output shaft connect to?
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That system will work just fine. You are using the mechanical pump as a lift pump feeding a service tank.
The only issue may be the same issue that is faced by long cars with mechanical diaphragm pumps and that is a prolonged period of cranking in order to prime the lift pump.
Have you considered an electric vane type pump that is internally regulated to carburettor pressure as the lift pump? You could use something like a Carter Black with a -8 line to the surge tank that would place minimal restriction on the pump and with only 7psi in a repeatable hose like Aeroflow 200 the risk of burst or delamination is low yet priming the surge tank will be as easy as letting the carter run for ten to fifteen seconds.
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>>16459710
>where does this output shaft connect to?
Blinker fluid injection pump.
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>>16459710
if you can find a toronado trans you could make it rwd unless you could source a v drive for cheap
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>>16459808
Is that a complete transmission?
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>>16459705
Pretty good idea man
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>>16459705
Not allowed, they have to be openly visible. It's a damned stupid rule.
>>16459710
Yeah, fuel temp was a bit of a concern, we only get to about 25*C in the summer though, so i'm hoping ambient temp might keep things down.
I'll be using a reverse rotation transfer case, making it 4wd. Impreza rear diffs at both ends.
>>16459746
Cheers, im thinking of putting a check valve at the inlet to the second tank, should save the fuel draining out and the little tank should run the engine long enough to generate a fresh feed.
I thought about a 2nd electric pump, but apart from being a cheapskate, i like the idea of the lines within the car being totally unpressurised. If the main supply line fails, there's nothing forcing fuel into it.
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Actually, i meant to ask, am i better off keeping the 2nd tank as high or low as possible in the car?
My thinking being that if it's too low, the head of fuel in the main tank might hinder the vent?
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>>16459880
Sounds like you've made up your mind then, and it's a good plan. Run the suction from a mechanical lift pump to the day tank which leaves only a small run of line around half a Bar to the surge tank and a very small run of line under five Bar. If you do use the mechanical pump no check valve will be needed as the valve set in the diaphragm pump will prevent leak down back to the day tank.
This is a really cool project! What's the donk, a 305 or 350 iron SBC?
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>>16459898
Either will be fine. At maximum the mechanical pump would put the service tank at half a Bar which would be enough to oppose the head of the fuel in the day tank but it shouldn't get that far provided the return line is a decent size.
Thread posts: 14
Thread images: 7
Thread images: 7