EFI conversion- low pressure fuel pump question

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volvoguy
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EFI conversion- low pressure fuel pump question

Post by volvoguy »

Hello, I'm in the process of putting a fuel injected engine into an initially carb'd car. So far I think I'm having a low pressure pump (facet solid state) feeding a swirl pot and the donor car's high pressure pump being fed from that. Return from the fuel rail will go straight back to the tank.

What I'm wondering is whether these kinds of low pressure solenoid pumps benefit from a pressure regulator being fitted to the swirl pot > tank return line or whether they're fine running at 100%.

Thanks
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Fred
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Re: EFI conversion- low pressure fuel pump question

Post by Fred »

I doubt running at 100% would do them any harm. You have to ensure that your facet pump can supply at least a little more than the EFI pump at ALL times, though, or it'll run dry. More traditionally you'd run a return from the high pressure pump to your swirl pot and the return from the swirl pot to the tank. Read this thread:

viewtopic.php?f=24&t=47

Fred.
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volvoguy
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Re: EFI conversion- low pressure fuel pump question

Post by volvoguy »

I'm not sure which of the facet solid state pumps I have, but the lowest spec one flows 10 US gallons/hour. I plan on a 1.5/2ltr swirl pot. It's not going to be a screaming engine, yet, so it should be ok.

I'd read that fuel which returns from the rail can be quite hot so it's better to pipe it to the tank. I suppose a difference in temperature doesn't have a massive effect on performance for a fast road setup.

Thanks for the link. Is your main tank annotation referring to a situation where the high pressure pump is removing more fuel from the surge tank than is being pumped into/returned to it?
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Fred
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Re: EFI conversion- low pressure fuel pump question

Post by Fred »

Yes, that's exactly what it's referring to. That situation should probably be avoided, though.

While it's true that the fuel coming back is hot, the fuel being cycled through by the low pressure pump is cool, so there is a heat exchange happening to the tank anyway.

I'll PM you a video of the vehicle I have that fuel system in so you can see how it well it works :-)

Fred.
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volvoguy
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Re: EFI conversion- low pressure fuel pump question

Post by volvoguy »

Well you make a rather convincing argument for using that fuel set up. I think as my surge tank will be towards the front of the car the fuel pipes might even work out a little cheaper this way. Win win. Thanks :)
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Re: EFI conversion- low pressure fuel pump question

Post by Fred »

You're most welcome! :-)
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