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
Unfortunately that is one of the drawbacks of a fuel return system.
With the 555 system all injector pulses rates and widths are the
same so one can build a simple flow meter that consists of diode
and large capacitor that will sum the pulse width and rate from
one injector. That sum can be read by a digital voltmeter to give
you a flow rate. It is calibrated with a pot so it can read
out GPH to the nearest .01 gallon. Very simple. Computers systems
do it the same way except they do it in software.
I might build the diode, capacitor and pot into one of the PC
boards. You have your choice of read outs. One can probably test
the scheme on a car EFI system.
Paul Lamar
Hi C. Smith,
If you consider running your 4 wing tank lines to a header tank, you can
run the return line to that. No muss or fuss with removeable wing
parts. That would be 4 lines into the header tank, then 2 lines to the
engine ( 1= flow to engine, and1= return ). Low pressure pumps or
gravity deliver fuel to the header tank and 2 high pressure pumps (1 'in
use' pump, 1 'back-up' pump) can be in an easily serviceable location
inside or next to the header tank depending on what type of pump you
select. The header tank should be at least 3 or 4 gallons to prevent
any fuel temperature buildup and have a sump drain petcock. Stick a
float switch in the header tank to activate a cockpit siren and you have
a "TIME TO LAND" emergency reminder ; ) Dave M
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