EFI fuel return line in tanks

G-force · #1 03-23-2007, 09:48 AM

Working on tanks for a -8 and want to install return lines for EFI system. Does anyone have any thoughts on the location of the return tube? I have heard return it to at least the 2nd or 3rd bay. Are you locating the end of the return line low in the tank so it is always submurged to prevent foaming or just allowing it to "waterfall" when the tanks are low on fuel? I understand you would not want to install the entire return line low in the tank as the pressure of a full tank of fuel would try and flow back through the return line, but I am thinking a sound plan would be to run the return line higher up in the tank near the vent line, then bend the end of the tube downward to the bottom fof the 3rd bay. Ideas or comments? Thanks.

rv6ejguy · #2 03-23-2007, 10:07 AM

EFI return lines need not dump way outboard. I've just used AN fittings with Earls Stato Seals mounted as high as possible on the tank service plate (RV6A) or inner tank rib (RV10). No problems to date but I also use a small header tank mounted behind the firewall to ensure fuel feed to the EFI pumps in all flight attitudes and no air entrainment.

dan · #3 03-23-2007, 12:48 PM

Quote:

Originally Posted by G-force

...as the pressure of a full tank of fuel would try and flow back through the return line...

Imho, for an AFP purge return, it'd be best to install a check valve in there somewhere. I didn't, but I definitely would next time.

DGlaeser · #4 03-23-2007, 01:34 PM

I put mine right in the center of the forward "cutout" stamped in the ribs. Just a straight pipe out to the 4th bay. Sounds like I could have made it shorter. Oh well. My returned fuel gets to take the scenic route

rv6ejguy · #5 03-23-2007, 01:55 PM

Not sure if you are talking real EFI or mechanical injection stuff? Your post said EFI. Two very different systems.

RScott · #6 03-23-2007, 02:05 PM

Talked with the rep from ECI a few weeks ago & he happened to mention that the return lines for their system should go high on the outboard end. I didn't ask why & don't know if he meant "should" or "must". Why not call the manufacturer of the system you'll be using?

FlyerJumper · #7 03-23-2007, 03:06 PM

I'm in the process of putting an AN fitting in the outboard rib of each tank. No internal tubing, just the fitting. Initial plans are to cap it off, but if I need it, the plan is to run the return line behind the tanks. I've also installed an access panel in the underside of each leading edge in order to get to these fittings should the need arise (not sure about the other models, but the -10 installs one of these panels for access to the stall warning. I just installed another one in the other leading edge since it was in the perfect position to access these return fittings).

rv8ch · #8 03-24-2007, 12:12 AM

There is a lot of discussion of this topic here:

http://www.vansairforce.com/communit...ead.php?t=2627

T.Green · #9 03-24-2007, 09:06 AM

Mike,
Here is what Jan Eggenfellner (Subaru engine) tells his builder to do. Look at Diagram of EFI fuel return system. Hope this helps.
http://www.eggenfellneraircraft.com/fuel.htm