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Swirl Pot Return
ttalps2000 - 4/3/20 at 08:26 AM

In the process of plumbing in my swirl pot. I am running a returnless system, so all i have coming into the swirl pot is the low pressure pump feed. I am struggling to find a position to put the overflow from the swirl pot back into the tank. However, i am running a Facet cube style pump for the low pressure feed. These pumps are designed for running with carbs, which have a float chamber and shut off the fuel flow when this is full.

So, question is, do i actually need a overflow from the swirl pot back to the tank? I see no issues with just blanking this off and letting the low pressure pump fill the pot up. Only issue could be a air pocket at the top of the swirl pot i guess?

If not, any easy ideas on getting a return connection into the tank? I was going to put it into the fuel sender, however it is too small to do so, so that option is out!

40inches - 4/3/20 at 09:33 AM

I ran the return back to the tank breather outlet and made another breather.
As you said the return is to bleed off any air, brake line is big enough, I have a 0.8 mig nozzle in the rubber tube from the swirl pot return.
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voucht - 4/3/20 at 10:44 AM

Hi,

I would install a return hose anyway, even with a self-interrupting Facet LP fuel pump.

Here are some 3D schematics swirl pot installations I did a few years back when I was working for a company involved in hydraulic circuits for racing cars. The difference between the 2 schematics is if you have a 2 or a 3 ways fuel pressure regulator.

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Red cylinder = fuel filter
silver cylinder = high pressure fuel pump
golden cube = low pressure fuel pump
golden dome = fuel pressure regulator.
And I think it is pretty obvious where the swirl pot, the fuel tank and the interjection ramp are on the systematics

Hope that will help

ttalps2000 - 4/3/20 at 10:55 AM

The issue im getting is that i dont really want to drop the tank out and start drilling holes in it to get a fitting put in etc!

voucht - 4/3/20 at 11:03 AM

Now I'm not sure I understood your first post. Are you running an injection (high pressure) or carbs (low pressure)?

ttalps2000 - 4/3/20 at 11:29 AM

Injection, high pressure

indykid - 4/3/20 at 11:38 AM

quote:
Originally posted by ttalps2000
The issue im getting is that i dont really want to drop the tank out and start drilling holes in it to get a fitting put in etc!


One of these? https://www.parts4aircraft.com/fuel-tank-fitting-c2x9383165

Drill a hole, poke it in. No welding required.

There has to be a reason I've been saving this link all this time...

SPYDER - 4/3/20 at 12:00 PM

If you run too large a return from the swirl pot the low pressure pump will run at 100% all the time.
I have plumbed in a similar system to yours on my car. I have a pressure regulator after the LP pump set at around 1 or 2 psi which gives the LP pump something to work against. I also put a restrictor in the tank return line. I ended up at around 1mm IIRC. The LP pump still never actually stops clicking but it is running a lot slower. The possible downside of this is that the swirl pot is slightly pressurised but this hasn't caused any problems for me.

dhutch - 4/3/20 at 02:53 PM

quote:
Originally posted by SPYDER
If you run too large a return from the swirl pot the low pressure pump will run at 100% all the time.
Is this a problem? (genuinely dont know)

SPYDER - 4/3/20 at 05:33 PM

I don't know if it would be a problem with your pump either. I know that mine made a right racket if left running at full chat.

rusty nuts - 4/3/20 at 05:35 PM

quote:
Originally posted by dhutch
quote:
Originally posted by SPYDER
If you run too large a return from the swirl pot the low pressure pump will run at 100% all the time.
Is this a problem? (genuinely dont know)


40 Inches has already suggested a solution in his reply

SPYDER - 4/3/20 at 08:02 PM

quote:
Originally posted by rusty nuts
quote:
Originally posted by dhutch
quote:
Originally posted by SPYDER
If you run too large a return from the swirl pot the low pressure pump will run at 100% all the time.
Is this a problem? (genuinely dont know)


40 Inches has already suggested a solution in his reply


...and I agree with him.

ttalps2000 - 13/3/20 at 10:53 AM

used one of these in the end: https://www.parts4aircraft.com/fuel-tank-fitting-c2x9383165

Seems to work well and installed within 10 mins! Just hope it doesnt leak now!

Also added a 0.8mm mig tip to add some back pressure etc

Mr Whippy - 13/3/20 at 12:05 PM

quote:
Originally posted by ttalps2000
used one of these in the end: https://www.parts4aircraft.com/fuel-tank-fitting-c2x9383165

Seems to work well and installed within 10 mins! Just hope it doesnt leak now!

Also added a 0.8mm mig tip to add some back pressure etc


What about swarf from drilling the hole?

ttalps2000 - 13/3/20 at 12:09 PM

coated the drill in grease and caught the majority of it all. Pump and tank has filters to catch any small bits

40inches - 13/3/20 at 12:14 PM

quote:
Originally posted by ttalps2000
coated the drill in grease and caught the majority of it all. Pump and tank has filters to catch any small bits


That's what I did, using a step drill. I used the Aircraft fitting for the breather and used the welded in breather for the return.
Both are on top of the tank so not submerged in fuel.

[Edited on 13-3-20 by 40inches]