Fuel Return Line Question

[440brew]

Question is - where does the fuel start its return to the cell, from the regulator or before?

I have a 68 Barracuda that I will be drag racing and the fuel cell has two ports at the sump.

Thanks!

 

[daredevil]

bypass at the regulator

 

[oiiiiiio]

i`m no expert on this stuff but first of all do you need to use a bypass? if so, i`ve heard you should never place a return line next to a supply port on the cell. something to do with turbulating (hope i spelled that right?)... the fuel flow. best to contact one of the techs @ like QFT or AED. good luck

 

[daredevil]

using a bypass is nessasary on the street so your pump isnt always fighting full pressure causing a pump failure

 

[BOA]

For race applications, you should have a no. 6 line off the regulator back to tank. You should try to return it in the top of the tank (opposite of the fuel exit)and add a tube inside directing to the floor of the tank, about 1/2 of the floor of the tank. If there is foam in the tank it helps keeping the turbulence out to some degree.

 

[Revhendo]

For race applications, you should have a no. 6 line off the regulator back to tank. You should try to return it in the top of the tank (opposite of the fuel exit)and add a tube inside directing to the floor of the tank, about 1/2 of the floor of the tank. If there is foam in the tank it helps keeping the turbulence out to some degree.

I've always learned that you want the return away from the pick up to prevent turbulence and airating the fuel in the cell. Or as I first heard it.
"Bubbles no bueno."

 

[godfatherofchry]

return??????????????

are you shour u need it.it is the ideal fuel syetm you run a dirict line to cab with a feul log put the reg. opest end of in.set fuel psi.and return that to tank opaset the out.

 

[BOA]

Am I sure you need it, No. I run Aero Motive fuel systems on my race cars. If you listen to them, they suggest you do. One thing I can say, I was having problems with the fuel pressure bouncing around on my max wedge car and I was concerned seeing the high spikes when driving around the pits or to the lanes with the Carters, the floats don't like that. So I added a no. 6 line off the regulator back to tank and it stabilized the fuel pressure. Didn't show up on the time slip but I sleep better.

 

[Crackedback]

Some pumps have a return outlet built into the pump.

If you don't have a pump with a return outlet, you might want to run a return style regulator. Cuts down on wear on your pump. The return line would be most dependent on your pump output. I run the mallory 250's and use #10 for the feed and return line. I almost always size the return line the same size as the feed side. Some guys say a 150-200gph pump needs a #8 return, a 250 needs #10, etc.

Don't put the return next to your cell outlet ports. Best thing to do is fit a tube into the tank for the return line so the fuel gets returned near the bottom. There are a lot of different ways to do the return at the cell. My return lines are always as far away from the outlet ports as possible. I haven't had much issue when there is foam in the cell. Seems to buffer a lot of return flow issues.

 

[440brew]

Thanks for the help guys... as it turns out my regulator does not have the return port so for now I will forgo this option. I may however replace the regulator in the future and run the return line.

I have a problem with the fuel pressure increasing to about 12 pounds under throttle. I am told it should be 7-9 constantly at idle to full throttle, can anyone confirm this?

 

[Meep-Meep]

I've always heard you only need 5-7 PSI and that's what I set my car to when I was racing. High pressure = restriction so a large line with few sharp bends should be the best thing. I can see a return being useful to control or damp fuel flow. Another thing, if you look at the size of the hole in a Holley or Carter needle and seat I'd say there's only so much you can get through there and huge lines may be unnecessary for a gas application.

I built a temporary system on my Porsche 911 to use the 12 PSI injection pump with carbs. I used a Holley low pressure regulator with one end going to the carbs and the other end to the factory return line through a .100 Holley jet. Even with the regulator the factory pump was able to overwhelm it and flood the carbs so I had to do something. I ran the carbs at 3-4 PSI and never ran out of fuel at high RPM.