Fuel return line?

[nacoblio]

So I am wondering about fuel return lines. I do not even have a clue has to the type of engine that I am going to put in my 7 but I wanted the option if I needed it. So I put a return line on my right tank. I am in the process of building my left tank and wondering if I can just run a dedicated fuel return line to the right tank and not have one on the left? I understand that I would need to be aware of running fuel out of the right wing first to avoid running fuel from the left and overfilling the right. Is this a good option or could it lead to problems that I am not even thinking of? If I do end up putting a return line in both tanks how hard is it to plumb the fuel selector? Thanks for the info.

[Bevan]

I believe this has been discussed in the forums, so might by worth a search. In my case, I didn?t know what engine I would eventually buy so i put a return to both tanks and a duplex Andair fuel selector valve. I ended up installing a lycoming with Precision fuel injection (not requiring a return line) but I use the return lines anyway for circulating fuel (via Airflow Performance purge valve) and to shut down the engine by depressurizing the fuel spider. This limits the amount of fuel pushing into the cylinders after heating in the lines after shutdown causing classic hot start issues and oil being washed off cylinder walls. That?s the theory anyway. It seems to work well for me.

Bevan

[Robin8er]

I would install a fitting for it now. I did not plan to install a return line, but wound up needing one. I only have a return line in the left tank, so as you mentioned the fuel only returns to the left tank. Its not really a problem in my opinion, you just spend more time burning off the left tank than the right.

Even if you wind up not using it, its not a problem and its there just in case you ever use it down the road.

You could but the fancy andair valve, but its not cheap.

[Ralph Inkster]

If you want to prepare for the possibility of using Electronic Fuel Injection, these systems require a return line to each tank. These systems circulate the fuel thru the system at over 30gal/hr, the reason the return fuel needs to go to the feed tank. If you already installed a fitting in one tank, you should follow thru & put one in the second tank while it is convenient to do so.
If your final choice is either carburetor or mechanical injection, its easy enough to plug off these fittings.

[rv7charlie]

I'd certainly put the fitting in both tanks; much easier to do now & easy to cap if you don't use it.

But the road less traveled for return type systems is to feed all fuel from one tank, and use a transfer pump.

[Hartstoc]

Originally Posted by nacoblio

So I am wondering about fuel return lines. I do not even have a clue has to the type of engine that I am going to put in my 7 but I wanted the option if I needed it. So I put a return line on my right tank. I am in the process of building my left tank and wondering if I can just run a dedicated fuel return line to the right tank and not have one on the left? I understand that I would need to be aware of running fuel out of the right wing first to avoid running fuel from the left and overfilling the right. Is this a good option or could it lead to problems that I am not even thinking of? If I do end up putting a return line in both tanks how hard is it to plumb the fuel selector? Thanks for the info.

I?d definitely recommend at least fittings in both tanks. Use of the Andair dual compound shutoff valve will always insure that fuel is returning to the same tank it came from. This is essential because all of the commonly used feul pumps are returning 20-60GPH to the tank continuously.

Dual return lines will also allow you to safely remove your engine driven pump in favor of a dual electric pump setup, with huge advantages for all types of fuel injection.(see http://www.vansairforce.com/communit...=Anatomy)-Otis

[Draker]

I had a similar question here, similarly had not selected my engine yet: http://www.vansairforce.com/communit...d.php?t=167215

Based on the discussion there, I decided it was enough to build the tanks with return plumbing but NOT plumb return lines through the fuselage unless and until I actually need them.