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  #1  
Old 01-19-2014, 06:41 PM
Future RV 9 Flyer Future RV 9 Flyer is offline
 
Join Date: Sep 2011
Location: Marathon,WI
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Default Fuel return line

I am about to close up the fuel tanks on my 9 but have questions about needing a return line if going with fuel injection.Is a return line needed with all fuel injection systems?thanks in advance !dh
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  #2  
Old 01-19-2014, 06:50 PM
SHIPCHIEF SHIPCHIEF is offline
 
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Location: Seattle
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Not needed with all systems, but they are needed with some systems, like any modern Automotive based Electronic Fuel Injection system that uses a fuel return regulator to control fuel pressure to the electronic fuel injectors.
That was a mounth full
If you think you might go that route, you might want to install a bulkhead fitting in the tank, and put a cap on it so you can hook up to it later without taking the tank off the wing?
I have such a system on my RV-8.
Be mindful that changes to the original plans will take time and add expense + weight.
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  #3  
Old 01-19-2014, 06:52 PM
Scott Hersha Scott Hersha is offline
 
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Location: Cincinnati, OH
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It's not required for all fuel injection systems, but is required on at least two popular ones. It's far easier to pro-seal a fitting in the tank now, with a capped off end, than removing the tank to do it later. The new RV14 tanks have that provision as standard equipment, even though many people won't need it. There is a hole in the inboard rib and a fitting that come as standard equipment in the kit. I would put it in if I were you....... (#6 AN fitting)
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Last edited by Scott Hersha : 01-19-2014 at 06:56 PM.
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  #4  
Old 01-19-2014, 09:16 PM
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airguy airguy is offline
 
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Location: Garden City, Tx
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Agreed with the two opinions above - some need it, some don't, and it will never again be as easy to put it in as it is right now.

I would suggest putting one in and capping it, you can always use it (or ignore it) later as you wish. Quite a few folks worry about foaming in the first bay where the fuel pickup is, from the fuel return line dumping in there. I put my return line AN fitting fairly high in the tank end plate, and routed an internal line through the first bay bulkhead so the return fuel dumps into the second bay, and gravity-flows along the bottom of the tank back to the fuel pickup, to minimize any chance of air bubbles or foaming making their way back to the fuel pickup.
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  #5  
Old 01-20-2014, 04:26 AM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by airguy View Post
Agreed with the two opinions above - some need it, some don't, and it will never again be as easy to put it in as it is right now.

I would suggest putting one in and capping it, you can always use it (or ignore it) later as you wish. Quite a few folks worry about foaming in the first bay where the fuel pickup is, from the fuel return line dumping in there. I put my return line AN fitting fairly high in the tank end plate, and routed an internal line through the first bay bulkhead so the return fuel dumps into the second bay, and gravity-flows along the bottom of the tank back to the fuel pickup, to minimize any chance of air bubbles or foaming making their way back to the fuel pickup.
I've done the same thing with my return line provisions, intending to fit an EFII system later on. It dumps out at the bottom of the second bay, several inches away from the hole at the bottom rear. It's a piece of cake to add when you're building the tank, and a big pain to do it later. I'd go ahead and provision for it now.
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  #6  
Old 01-20-2014, 05:03 AM
Stalldog Stalldog is offline
 
Join Date: Oct 2011
Location: Kansas
Posts: 332
Default Equal Flow Back to Tanks?

Another question if you don't mind. How is the fuel flow back to the tanks regulated so that the flow is relatively equal? What keeps one tank from getting more fuel, and weight, than the other?
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  #7  
Old 01-20-2014, 05:45 AM
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MikeyDale MikeyDale is offline
 
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Location: Garden City Texas
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I believe you will would need to install a "Duplex" fuel selector. It returns fuel back to the left tank when pulling from the left tank and same for the right tank. The valve is like a double valve. Here is a link showing a picture of the FS 20x20-3 duplex valve, http://www.andair.co.uk/system/index.html. Vans has one on the website. http://vansaircraft.com/cgi-bin/stor...selector-valve. FS 20X7T is the single Andair valve and a FS 20x20-3 is the duplex. Both are listed on this page......The believe biggest obstacle when going this rout is the plumbing. Things can get mighty crowded under that fuel valve cover!
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  #8  
Old 01-20-2014, 10:44 AM
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Mark33 Mark33 is offline
 
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Location: Baton Rouge, La.
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Quote:
Originally Posted by MikeyDale View Post
I believe you will would need to install a "Duplex" fuel selector. It returns fuel back to the left tank when pulling from the left tank and same for the right tank. The valve is like a double valve. Here is a link showing a picture of the FS 20x20-3 duplex valve, http://www.andair.co.uk/system/index.html. Vans has one on the website. http://vansaircraft.com/cgi-bin/stor...selector-valve. FS 20X7T is the single Andair valve and a FS 20x20-3 is the duplex. Both are listed on this page......The believe biggest obstacle when going this rout is the plumbing. Things can get mighty crowded under that fuel valve cover!
Yes, the duplex valve takes care of the routing the fuel back to where it needs to go. Be sure to get the 90 degree fittings for the valve....it really makes the plumbing easy.
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  #9  
Old 01-20-2014, 11:25 AM
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JanRV6UK JanRV6UK is offline
 
Join Date: Jul 2009
Location: England
Posts: 470
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Simple question I could probably find if doing a search ....

Which FI system does not require a return line to the tank ... and what are the downside ?? I need to be thinking about a engine purchase ... 360 with a CS prop .. I have not fitted a return line fitting to the tanks .. Yes at this point in time I could pull the tank off the wings and install one .. but doing it in the section furthest away from the suction strainer will require a access hole cut in the rear. ... and I do not fancy all that extra piping in the cabin (RV6) ... Appreciate some thoughts on this ...
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  #10  
Old 01-20-2014, 12:33 PM
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Jerry Cochran Jerry Cochran is offline
 
Join Date: Jan 2005
Location: Sherwood, Oregon
Posts: 981
Default Returns for AFP F.I.

The -6a I sold to Dale Walter with IO360 Superior had no return lines, while the -7a purchased from David Domeir with Barrow-built IO-360+Airflow Performance F.I. has return lines. I rebuilt the entire fuel system and got almost(!) all the plumbing inside of a Van's standard cover next to the 6 port Andair valve. A combination of alum and stainless flex hoses did the job.
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