Re: fuel system - return line
[Re: NITROUSN]
#3002883
01/07/22 02:34 PM
01/07/22 02:34 PM
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Joined: Jan 2005
Posts: 1,772 Keymar, MD
DusterKid
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,772
Keymar, MD
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On my cars I always get it as far away from the supply port as possible. I also extend it down into the fuel about 3 or 4 inches from the bottom of the tank. What do you use to extend the line? Alum fuel line?
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Re: fuel system - return line
[Re: DusterKid]
#3002895
01/07/22 03:23 PM
01/07/22 03:23 PM
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Joined: Jan 2003
Posts: 18,419 UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,419
UPPER MICHIGAN, MARQUETTE COUN...
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On my cars I always get it as far away from the supply port as possible. I also extend it down into the fuel about 3 or 4 inches from the bottom of the tank. What do you use to extend the line? Alum fuel line? Most of the time just a bulkhead fitting and a short most likely 8an hose in the tank.
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Re: fuel system - return line
[Re: DusterKid]
#3002924
01/07/22 04:38 PM
01/07/22 04:38 PM
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Joined: Aug 2003
Posts: 43,176 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,176
Bend,OR USA
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On my cars I always get it as far away from the supply port as possible. I also extend it down into the fuel about 3 or 4 inches from the bottom of the tank. What do you use to extend the line? Alum fuel line? It is your choice, soft aluminum tubing flared to AN 37 degree flare with a AN female fitting or AN hose with a female fitting on it I haven't ran the return line on my new car yet but I'm thinking a aluminum line ending up about two inches from the bottom
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: fuel system - return line
[Re: Cab_Burge]
#3003197
01/08/22 03:18 PM
01/08/22 03:18 PM
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Joined: Sep 2003
Posts: 19,405 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,405
north of coder
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and now for the old guy DUM question of the day.......... i have read, and been told many times by many different people, the return line should be LARGER, SAME SIZE, and SMALLER in diameter. these have been on successful installations, so if it is successful and works, it must be ok. i like the idea of larger, or possibly the same size. less likely to cause residual heat buildup in the fuel system. it is also quite possible a smaller line would work if there were not much fuel being returned to the tank. so, any return line is better than nothing, depending of course, the system design itself ?
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Re: fuel system - return line
[Re: Cab_Burge]
#3003231
01/08/22 05:49 PM
01/08/22 05:49 PM
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Joined: Dec 2005
Posts: 11,566 Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,566
Fulton County, PA
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I would use the same size line so it is not an unintended restriction.
Return to the tank below the fuel level prevents aeration.
If the results don't match the theory, change the theory.
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Re: fuel system - return line
[Re: dragon]
#3003543
01/09/22 07:01 PM
01/09/22 07:01 PM
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Joined: Dec 2016
Posts: 1,111 Usa
A39Coronet
super stock
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super stock
Joined: Dec 2016
Posts: 1,111
Usa
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Just thinking wouldn't a bigger return line be better because it would reduce pressure going back to the tank reduce stiring up thing in the tank a smaller line would more presure comeing out to keep up with the return flow ??? The pressure in the return line is already lower than the feed side. I would think larger to be unnecessary, but personally I wouldn't go smaller than the feed.
Last edited by A39Coronet; 01/09/22 09:57 PM.
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Re: fuel system - return line
[Re: A39Coronet]
#3004012
01/11/22 02:08 AM
01/11/22 02:08 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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Aeromotive directed me to make the return line the same size as the supply. I’m at -8 on both, with -6 from the regulator to the carb. Return is routed to the top front of the cell, but not extended. May be a good idea as it could cut down on aeration.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: fuel system - return line
[Re: StealthWedge67]
#3004443
01/12/22 07:53 AM
01/12/22 07:53 AM
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Joined: Dec 2016
Posts: 1,111 Usa
A39Coronet
super stock
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super stock
Joined: Dec 2016
Posts: 1,111
Usa
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Aeromotive directed me to make the return line the same size as the supply. I’m at -8 on both, with -6 from the regulator to the carb. Return is routed to the top front of the cell, but not extended. May be a good idea as it could cut down on aeration. I wouldn't think fuel would hold the aeration in a moderately sized tank. It's already in there sloshing around.
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Re: fuel system - return line
[Re: A39Coronet]
#3006464
01/18/22 11:33 AM
01/18/22 11:33 AM
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Joined: Jan 2003
Posts: 13,363 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,363
Marion, South Carolina [><]
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I have a stock tank w/ a sump for the pickup. I use the stock 3/8" pickup tube as my return, so it's submerged. I use a -10 feed and a -8 return...as directed by Aeromotive back in 2011 when I installed this system.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: fuel system - return line
[Re: an8sec70cuda]
#3006658
01/19/22 01:12 AM
01/19/22 01:12 AM
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Joined: Jul 2011
Posts: 781 wine country
8urvette
super stock
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super stock
Joined: Jul 2011
Posts: 781
wine country
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Holley told me -10 feed then use -6 return. The fpr is setup that way too. This is a MPFI fuel injection setup. However I have a -8 in place for the return. So yes there is a bottle neck from regulator, but I already had -8 installed from the last setup.
Last edited by 8urvette; 01/19/22 01:14 AM.
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Re: fuel system - return line
[Re: moparx]
#3006696
01/19/22 05:48 AM
01/19/22 05:48 AM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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and now for the old guy DUM question of the day.......... i have read, and been told many times by many different people, the return line should be LARGER, SAME SIZE, and SMALLER in diameter. these have been on successful installations, so if it is successful and works, it must be ok. i like the idea of larger, or possibly the same size. less likely to cause residual heat buildup in the fuel system. it is also quite possible a smaller line would work if there were not much fuel being returned to the tank. so, any return line is better than nothing, depending of course, the system design itself ? Found out it depends on the regulated pressure and pump volume. Have a setup with the older Mallory 250 GPH pump and by-pass regulator, both -8 AN supply and return. At idle, the fuel pressure would creep up one or two PSI, go from 7 to 8 or 9 psi. The pump also has a by-pass, so I set the pumps by-pass to just dump a small amount of fuel back into the fuel cell. Anyhow, I think High Volume pump and low regulated pressure like 6-7 psi, the return needs to be same size or larger than supply line. Also, non-boosted carb, the fuel pressure is normally just referenced (or regulated) to atmosphere, so fuel line pressure to vented bowl should stay the same under different loads. Anyhow, the pressure in the return line has to be lower than the regulated pressure, and pressure is a function on fuel volume, line diameter, and line length. Because the regulated pressure is only a few psi, the return line can't have much pressure in it, or pressure will start to increase. On my EFI stuff, it is different. The normal 225 lph pump is only about 60 GPH, and "regulated" pressure is 3 or 4 bar = 43.5 psi or 58 psi. By "regulated", that is usually referenced to manifold pressure, so the regulated pressure stays the same across the fuel injector (on return type EFI), but if you have a pressure gauge in the line it only shows the 3 or 4 bar pressure when the engine is not running. Under vacuum the gauge pressure will look lower because the gauge is referenced to atmosphere not manifold pressure. Anyhow, the largest EFI pump I tested on my car was the Walbro 450 lph (about 119 GPH) at 4 bar with 3/8" supply and 5/16" return and the smaller return line was not a problem. Because the regulated pressure is way higher, a small amount of pressure in the return line is not an issue.
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