It is sometimes difficult to mount fuel pumps in AC wings.
Most people don't do it. They mount the pumps on the firewall.
Paul Lamar
Paul,
I'm just starting construction of my fuel tanks for a Zenith CH-640.
I'm opting for a four wing tank system. I'll likely be using a 16b
conversion,
fuel injection based on your designs. With the discussion on-going about
in tank fuel pumps and fuel return lines, I am asking if I need to make
accomodation for anything special. Presently, my tanks have no
provision for
a fuel return or in tank pump. Would it be necessary to design in any
of this
stuff?
Thanks, C. Smith
Yes you might think of adding a large removable panel in the root
ribs for internal pumps. The 640 has a nice thick wing for internal
pumps. Looks like the tanks are in the leading edge. If not
practical use two lines from each tank. One for feed according
to the plans and one for return fuel.
Paul Lamar
Correction, I meant 13b engine.
C. Smith--
So the EFI system with a fuel return line would preclude the use of a
fuel flow meter to keep track of fuel used and burn, unless someone
knows of a meter that subtracts the return flow?
so with a 4 tank system, thats 8 fuel lines, and a tank selector valve
ganged 4x4? 4 separate fuel pumps, and control wiring?
No other way to do this? I'm bummin' out.
C Smith
C.
There are systems that will subtract the fuel return, but dont bother. Here
is what I recommend. It is what I did an I find it works very well.
Route your SINGLE return line to a tank you consider your 'main' tank. Not
a headder, but your largest tank. The fuel valve now has to select only
which tank you are drawing from, but you will obviously be using your main
tank most of the time. When you select one of the other tanks, the fuel
then is in essence being transferred to the main tank. That is OK. Will
transfer at a known rate of about a gallon/min. It is imperative that you
set some sort of alarm to avoid overflowing the main tank. I actually have
a fuel flow transducer on my RETURN line, and I set it to remind me after I
have transferred the desired number of gallons to the main tank.
This is simple and reliable. Only one simple return line, simple fuel
select valve, and only necessitates an alarm for when using one of the other
tanks.
As a fuel totalizer, use something that tallies the injector workload such
as Ed Anderson's EFI monitor or Tracy Crooks EM2. I have Ed's and it does a
very accurat job of keeping track of the fuel.
JMHO