Duplex fuel valve
 

I am looking for a suitable fuel valve for a EFI setup in a high wing plane (Bearhawk), and a IO-540. Its a dual tank, gravity fed system, and the designer highly recommends running the fuel valve in "both" for TO or Landing. I am having a hard time finding a suitable valve. The Andair valve that is sized right does not have a "both" setting. The Newton valve has one, but the returns are only 1/4", which I think is a little small for this application. At idle engine power, the electric pump would be pumping 23-24 gph through a 1/4" return line. Is the Newton valve adequate?

Groco makes one,FV-65038-A, that has 1/2" feed and 3/8" return lines. The price is right, but it weights 3 lbs. 3 lbs is less than a header tank, which I am trying to avoid if I can.

The stock fuel system works great in "both". The two tanks have a for and aft feed line, so in "both" you should have fuel feed no matter what angle of bank or nose up or nose down.

IIRC, the STC for the 180 HP installation in the C-170 requires a change to 1/2 inch feed lines. This seems a wise move considering the length of the lines compared to an RV. Add the fact that you are feeding a 540 and it becomes even more desirable. I was hesitant to keep the 3/8 lines in my Rocket but there is plenty of evidence it works. Do the 540 Bearhawk guys use 3/8 lines in practice?

OTOH, the 1/4 return is probably adequate since it is under pressure and will not suffer from the suction induced vapor pressure issues that the supply side will.

The aircraft plans call or 3/8" regardless of engine. Each tank has a for and aft 3/8" feed line, which are T-ed before they enter the fuel valve. The info I have for the EFI says 3/8" feed and return.

The stock system works well apparently. I haven't read of any issues. I am just having issues finding the right duplex valve. The Groco valve will work, but it weighs a lot. I was hoping to find a lighter alternative, or, if Newton valve is adequate. I suppose I could upguage the return line to 3/8" right after it exits the valve which should help the flow.

The pumps the EFI uses are 25 gph and are positive displacement. So whether the engine is idling, or a TO power, they should still be flowing 25 gph. At TO power the engine is using most of the fuel, and only a little will be returned. At idle, the return lines need to be able to flow almost all the fuel back to the tanks.

No problem!
 

I had to upgrade to 3/8? return lines using the Newton valve. If I recall correctly, the fitting is 1/8?NPT, with a #6 flare fitting? I bough one straight for the actual return from the regulator, and two ea 45deg adapter for the feeds to the tanks so the tank lines would run side by side.

I bought those parts from hydraulicsdirect.com, and this vendor sells steel fittings for about 25% of what a comparable alum fitting cost - so there is no reason to not use steel fittings firewall fwd any more.

Thanks,
I was wondering if that is how folks were using the Newton valve. I will check again but I think one of the Newton valves was 1/4" NPT. There was a smaller one also, I think 1/8.

I have the Andair duplex valve and it is my understanding that there is no “dead” position between the left and right positions. There cannot be for safety reasons. This being the case, putting the selector in between left and right would cause feeding from both. You may want to consult Andair before you discount their product as it is a work of art. Perhaps they have a faceplate with the word “Both” in the appropriate location.

edit: I don't believe "BOTH" should be a position used for constant fuel flow return systems.

Bevan.

I used the Newton SPRL V4 valve which has a full flow return valve/fuel selector - not the 1/4" that I think you are talking about with the V3. In fact the selector has 17mm threads into which a variety of fittings are available - AN8 included. I've been flying on it for a year and it works flawlessly. You can get the "Both" configuration like you say you need. Support from Robin at the company has been fantastic. I don't think you will be disappointed.

I will send both Andair and Newton an email. Thanks for the input.

From the Newton website, the V4 threads are a bit confusing. Cut and pasted.

"The return ports are tapped female for ? NPT fittings. Actually the return ports are tapped straight (NPS) to give more flexibility in orienting NPT elbows."

It doesn't exist (or at least it shouldn't) for a good reason.

I don't think a Both setting makes sense with a duplex valve (valve with returns). Where is the return fuel going to go when you have the valve set to Both? It might go to the left or to the right... you'll never really know.

If you are going to run a system that requires a return (such as EFI) then you need to be in control of where the return fuel goes (which should be the tank it came from).... therefore you need a Left / Right valve.

I agree and have amended my earlier post. I don't believe constant fuel flow return systems should use a "BOTH" position as it means fuel could flow back to both tanks but possibly not equally or appropriately.

Bevan