Fuel tank and pump setup with return style regulator.

I am also building an RCR with dual fuel tanks/cells, and am looking for a simple way to feed from both tanks. The mechanical 6 port transfer valve looks clunky and the electric Polak valve also looks out of place and overly complicated. It seems that a lot of modern cars with dual tanks (new corvette) or with hump tanks (BMW, Mazda) are running venturi jet pumps in the secondary tank. The jet pump feeds the primary tank. The primary tank feeds the surge tank with a lift pump. The surge tank with integrated pump and regulator feeds the fuel rail. Has anyone tried using a jet pump in the secondary tank? The downside of a jet pump is they eat up the main pumps volume and pressure rating.
 
Actually, if you're using the return from the regulator rather than an orifice from the pump output, it's a free lunch, as long as you don't create too much back pressure for the regulator to work correctly.

10 years ago when building my Cobra's fuel tank, I integrated a swirl pot inside the tank, and the fuel return feeds a venturi pump that keeps scavenges all of the fuel from the tank into keep the swirl pot full. It works great until you run out of gas with no warning other than the gauge not blipping up off the E mark.

A venturi pump in the main tank that sucked fuel from the secondary tank would be a brilliant and simple solution.

Another benefit of using the return from the regulator is the back pressure of the venturi pump's nozzle reduces the delta p at the regulator and reduces fuel heating just a little.
 

Davidmgbv8

Supporter
Cool technology, never heard of this style pump
Jet_Pump-Return_System.png
 
Excellent illustration.

I added 2 trap door baffles and a 1/2 gallon reservoir with a hand formed venturi pump. I tried it out in the swimming pool with a junk fuel pump an it very quickly filled the reservoir holding it where the inlet was barely submerged. I added the top baffle so the current rolled over back into it.
 

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Hi, on the Subaru Impreza fuel pump assembly you have the withe plastics and venturi effect. uses return flow to pump fuel near the intake of the main pump ..... this Principe is in use also on Audi A6 Quattro since 1998....
Paul
 

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I am definitely going with a jet pump from Radium. I just wanted to see if others have tried it. It looks like a much simThe only things I think need to be considered; 1) if you put the venturi on the return from the pressure regulator, it will increase the effective pressure of the regulator. The back pressure of the venturi will increase the pressure differential of the regulator. 2) if you put the venturi on the output of the pump it drops the output volume and pressure of the pump by some amount. Not sure if its enough to matter. Have to try it out.
 
As long as the back pressure from the venturi pump is 12 PSI below the regulator's target pressure, the regulator will still regulate and hold the intended pressure. I pulled 12 lbs out of thin air based on 4-5 lbs delta P at the regulator, and the reduced presssure referenced by the manifold vacuum.

If I remember correctly, I had a 1/16" orifice, and my Areomotive stealth pump at full flow was only 18 psi. As engine load increases, more of the fule is burned rather than bypassed by the regulator, reducing the back pressure. SO, if you're regulator isn't above 42 PSI or whatever you have it set to minus manifold vacuum at an idle, all is good.

Before posting, I looked up your Radian pump and found them on ebay. I was going to say, I've made them with just a TEE and a home made nozzle.

This one worked like a champ to feed a swirl pot mounted beside a gas tank. All 304 stainless plumbing hardware. The nozzle was a piece of 3/8 tubing I sliced and welded and prettied up.
 

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I manage to squeeze the swirl pot, regulator, lift pump and main pump along with the driver side fuel cell all in the RCR sponson on the left. I plan to seal the whole system under some plexiglass so if something leaks or ruptures, there is little to no risk of fire. To keep it simple i just connected the two tanks at the bottom.


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