-4AN Fuel Return Line

[EclipseOwner95]

So I have a bunch of left over -4AN line and fittings laying around and I was contemplating replacing the stock return with it. I searched and see that most people just run a -6AN return if their going to upgrade.

I don't really need to upgrade my return, just wouldnt mind getting rid of the factory hardline from the engine bay. Anyone see a problem with me doing so ? I figure a -4AN line is more of a lateral move than an upgrade. I tried searching for the factory OD/ID of the stock return but had no luck. As long as -4AN isnt smaller than the factory return I'm happy.

Thanks.

 

[Notstock]

I'm fairly certain the return line is .25 ID which would equal -4AN hose.

 

[Hal]

I'm fairly certain the return line is .25 ID which would equal -4AN hose.

Wrong answer

-4 I/D is approx .16" while -6 is approx. .25"

A/N sizing is based on the O/D of the hose (edit - actually the equivalent tube size), not the I/D

Hal

 

[Notstock]

Wrong answer

-4 I/D is approx .16" while -6 is approx. .25"

A/N sizing is based on the O/D of the hose, not the I/D

Hal

Grrr. I knew I was missing something when looking at the size chart. So in other words OP, don't use it.

 

[jpmxrider489]

If your going to upgrade your rerturn. I would go 6 an. Just in case you want bigger in the future.

 

[99gst_racer]

The I.D. of -4 will depend on which hose it is specifically. Take Aeroquip's hoses for example:

SS braided - .22"
Socketless - .25"
Teflon lined - .19"


I've never measured the factory return line, so I don't know what size it is.

 

[EclipseOwner95]

Thanks for the responses. So I guess the million dollar question is, is a -4AN line smaller, the same, or larger than the stock return line. Unfortunately I already ripped mine out, and threw it away so no way for me to measure my own.

 

[talonalex92]

The stock return is 1/4 od. I am 100% certain, as I just re did mine in -6, and measured it just for shits and gigs. Depending on the line you use, it may or may not be smaller. I would measure it before you shrink it.

 

[sparky1987]

I would go with -6an on the return side that's probably closer to the factory size if not maybe a touch bigger. The extra flow wouldn't hurt any -4 is good for oil feed line on a turbo and brake lines if its approved to handle the brake fluid.

 

[Boosted98gsx]

Hell if you're going to do the full return, do it right and plumb it as large as you can, that way you'll never have to do it again.

I would go with -6an on the return side that's probably closer to the factory size if not maybe a touch bigger. The extra flow wouldn't hurt any -4 is good for oil feed line on a turbo and brake lines if its approved to handle the brake fluid.

Incorrect, factory return line is 6mm ID if my memory serves me, which would be larger than the ID of a SS braided -6an, which is the only thing (for its robustness) that you should run under a chassis that's not a hard line.

Unless you're going to do -8 or larger all the way back, don't waste your money.

 

[estoyaqui30]

besides, I'm not sure if it's just me, but the factory retune line (99 GSX) is already on the small side. I'm running a Walbro 255HP with a Aeromotive AFPR and I can't get the fuel pressure down low enough to meet Mitsu spec at idle. I'm not positive but I believe that a -6 is a fraction over factory.

 

[Boosted98gsx]

besides, I'm not sure if it's just me, but the factory retune line (99 GSX) is already on the small side. I'm running a Walbro 255HP with a Aeromotive AFPR and I can't get the fuel pressure down low enough to meet Mitsu spec at idle. I'm not positive but I believe that a -6 is a fraction over factory.

Nope, factory feed and return on 2g's are larger then -6an braided.

 

[estoyaqui30]

Nope, factory feed and return on 2g's are larger then -6an braided.

Sorry, my bad. I was assuming that because the outlet of the AFPR is a -6 and I have a russell -6 90˚for push on hose. the hose is slipped on to the factory return hard line and clamped so....I assumed they were close. I had run braided SS -6 line both, to and from the tank and after a week of the car smelling like a rolling fuel leak, I pulled it back out.

 

[compression]

besides, I'm not sure if it's just me, but the factory retune line (99 GSX) is already on the small side. I'm running a Walbro 255HP with a Aeromotive AFPR and I can't get the fuel pressure down low enough to meet Mitsu spec at idle. I'm not positive but I believe that a -6 is a fraction over factory.

If you cant get down to 43psi of fuel pressure i think you may have an underlying problem, i have the same regulator, with a 255 feeding a bosch 044 with stock return lines, and i can go under 30psi.

i know this is from a 1g, but they might be similar , i dont know..

Factory return line.

<a href="http://s48.photobucket.com/albums/f224/mxdawg121/?action=view&amp;current=IMAG0631.jpg" target="_blank"><img src="http://i48.photobucket.com/albums/f224/mxdawg121/IMAG0631.jpg" border="0" alt="Uploaded from the Photobucket Android App"></a>

<a href="http://s48.photobucket.com/albums/f224/mxdawg121/?action=view&amp;current=IMAG0632.jpg" target="_blank"><img src="http://i48.photobucket.com/albums/f224/mxdawg121/IMAG0632.jpg" border="0" alt="Uploaded from the Photobucket Android App"></a>

-4 ( i know its a fitting, i dont have any -4 that i want to cut up to measure )

<a href="http://s48.photobucket.com/albums/f224/mxdawg121/?action=view&amp;current=IMAG0638.jpg" target="_blank"><img src="http://i48.photobucket.com/albums/f224/mxdawg121/IMAG0638.jpg" border="0" alt="Uploaded from the Photobucket Android App"></a>
-6

<a href="http://s48.photobucket.com/albums/f224/mxdawg121/?action=view&amp;current=IMAG0635.jpg" target="_blank"><img src="http://i48.photobucket.com/albums/f224/mxdawg121/IMAG0635.jpg" border="0" alt="Uploaded from the Photobucket Android App"></a>

-8
<a href="http://s48.photobucket.com/albums/f224/mxdawg121/?action=view&amp;current=IMAG0636.jpg" target="_blank"><img src="http://i48.photobucket.com/albums/f224/mxdawg121/IMAG0636.jpg" border="0" alt="Uploaded from the Photobucket Android App"></a>

 

[estoyaqui30]

If you cant get down to 43psi of fuel pressure i think you may have an underlying problem, i have the same regulator, with a 255 feeding a bosch 044 with stock return lines, and i can go under 30psi.

Okay, that's good to know. I will have to call Aeromotive and see if I can get a rebuilding kit and if there are different spring rates. I that fails, I will look into a new AFPR.

 

[compression]

Okay, that's good to know. I will have to call Aeromotive and see if I can get a rebuilding kit and if there are different spring rates. I that fails, I will look into a new AFPR.

Try another gauge first, if you are using the one little one on the afpr they can go bad after a while, they are meant to put on , checked , and taken off when done.

 

[crimsondragon]

A/N sizing is based on the O/D of the hose, not the I/D

Hal

Definitely not. Don't know where you're getting that info from but hoses are measured by I.D.

Tubing is measured by O.D.

Hell if you're going to do the full return, do it right and plumb it as large as you can, that way you'll never have to do it again.



Incorrect, factory return line is 6mm ID if my memory serves me, which would be larger than the ID of a SS braided -6an, which is the only thing (for its robustness) that you should run under a chassis that's not a hard line.

Unless you're going to do -8 or larger all the way back, don't waste your money.

What??? 6mm is about 1/4".
-6 hose is 3/8" I.D. Last I checked 3/8 > 1/4. -8 is overkill for stock to mild setup.


Seriously, where are you guys getting this info from???

 

[compression]

I have personally never in my life seen or heard of anybody having an issue with the stock return line not flowing enough fuel. generally on high horsepower cars, most of the fuel is being consumed by the engine.
go -6 if you want it to look nice, you may not have a problem, but i would not go -4.

 

[Hal]

Definitely not. Don't know where you're getting that info from but hoses are measured by I.D.

Tubing is measured by O.D.



What??? 6mm is about 1/4".
-6 hose is 3/8" I.D. Last I checked 3/8 > 1/4. -8 is overkill for stock to mild setup.


Seriously, where are you guys getting this info from???

Peterson Fluid Systems:FAQ

Bottom of the page

AN Size Tube OD Thread Size Hose ID
-4 1/4" 7/16-20 7/32"
-6 3/8" 9/16-18 11/32"
-8 1/2" 3/4-16 7/16"
-10 5/8" 7/8-14 9/16"
-12 3/4" 1 1/16-12 11/16"
-16 1" 1 5/16-12 7/8"
-20 1 1/4" 1 5/8-12 1 1/8"


Plumbing
AN Thread Sizes

AN (Army-Navy) sizes were established by the aircraft industry and designate the outside diameter of rigid tubing that the corresponding fittings are used with. Each dash size equals 1/16 of an inch. (ie -8 AN = 8 x 1/16" = 1/2" OD of the metal tube) Each standard AN size has its own standard thread size. Since the tube sizes do not equate with the hose sizes, due to the variation in wall thickness, the ID of the hose and tubes are not the same.

 

[crimsondragon]

Peterson Fluid Systems:FAQ

Bottom of the page

AN Size Tube OD Thread Size Hose ID
-4 1/4" 7/16-20 7/32"
-6 3/8" 9/16-18 11/32"
-8 1/2" 3/4-16 7/16"
-10 5/8" 7/8-14 9/16"
-12 3/4" 1 1/16-12 11/16"
-16 1" 1 5/16-12 7/8"
-20 1 1/4" 1 5/8-12 1 1/8"


Plumbing
AN Thread Sizes

AN (Army-Navy) sizes were established by the aircraft industry and designate the outside diameter of rigid tubing that the corresponding fittings are used with. Each dash size equals 1/16 of an inch. (ie -8 AN = 8 x 1/16" = 1/2" OD of the metal tube) Each standard AN size has its own standard thread size. Since the tube sizes do not equate with the hose sizes, due to the variation in wall thickness, the ID of the hose and tubes are not the same.

Ok so where does it say that hose is identified by the O.D.? The fact that they show the I.D. of hose in comparison to rigid tubing which is O.D. strengthens my point. Also those diameters are from high pressure hoses (>3000 psi) mostly found in aircraft hydraulics.

 

[ramsack]

http://timramich.com/crap/an_fittings.pdf

 

[Hal]

Ok so where does it say that hose is identified by the O.D.? The fact that they show the I.D. of hose in comparison to rigid tubing which is O.D. strengthens my point. Also those diameters are from high pressure hoses (>3000 psi) mostly found in aircraft hydraulics.

Missed the part in bold did you?

-8 is 8/16" based on the O/D of the equivalent tube size, not 8/16" I/D hose size

So, A/N is based on O/D size

I went back and did an edit on my original post, happy now?

Look at Pauls post (#6) and the different I/D sizes of -4. According to you they should all be nominally .25.

 

[crimsondragon]

Missed the part in bold did you?

-8 is 8/16" based on the O/D of the equivalent tube size, not 8/16" I/D hose size

So, A/N is based on O/D size

I went back and did an edit on my original post, happy now?

Look at Pauls post (#6) and the different I/D sizes of -4. According to you they should all be nominally .25.

I can roll with that.

I've always been drilled that dash hoses is exactly their size in accordance to their number. Of course that doesn't seem to be the case. As long as it fits their corresponding fittings, that's fine by me.

 

[ramsack]

AN is based off tubing size, OD, that's why the ID does not match the -AN number in sixteenths. You can mate a tube to an AN fitting flare by flaring the tube.

 

[SHEARER_TSI]

I feel that -6 is plenty for return line. My setup is -10 feed with a -6 return I see no reasn to go with a bigger return line.