Subject: Fuel system
From: ACRE
Date: 6/13/2003, 7:48 AM


The only modification to Vans standard is replacing the
single pump with the
dual, and the extra return plumbing. There was a thread
a while ago where a
guy got a dual valve made more cheapy.  You could also
use two normal valves
and gang them on a common shaft or with a linkage.

Another excellent, proven option is Tracy's main
tank/aux tank system, where
the fuel system draws and returns from one tank, and
the other tank just has
an LP transfer pump feeding the main tank.

Ed uses the standard RV system firewall aft (correct me
if I'm wrong Ed)
with fuel raill return fuel looping back to a header
tank before the HP
pumps (same idea as the Subaru mentioned). Although
this system has the
concern of vapour lock due to looping fuel heating up
at low power settings,
Ed must have over 350 hours on his, and has operated
into Florida heat.

Personally I'd rather have the HP pumps and filters in
the chambers under
the floor on the RV-4 than forward of the firewall, as
fuel spraying there
has lees ignition sources.

Regards,
Mark Wrathall


Thanks Mark, I see your point. My idea was to eliminate the
high pressure fuel lines from the cockpit area, so I came up
with the idea of using an electric six port valve on the
engine side of the fire wall. The fuel pumps would be located
either in the wing root or in the little fairings that RVs
have on the bottom of the fuselage aft of the firewall. The
same switch that actuated the electric tank valve would
select the apropriate fuel pump. Then I thought 'if the pumps
each have anti backflow valves, then why even have a selector
valve?' The down side is that you would have to have some way
to switch the fuel return to the tanks, and you would have
make some sort of method to run both pumps for takeoff and
landing. The problem here is that like you mentioned, with
full fuel tanks, your fuel return is going to vent overboard
from whatever tank the return is going to.

Well, there are several options here. I'd like to avoid
having to buy one of those extremely nice but pricey Andair 6
port fuel selectors.

I'm considering having one fuel pump per tank, going to a
my fuel filter,which has two inlets. The selector would be a
switch right next to return valve. To run both pumps
simultaneously, I have a momentary on switch on my throttle.
Rich Martin suggested a microswitch on the forward throttle
stop, perhaps with a disable switch nearby.

This is getting a little complicated, which might be a sign
that I'm going down the wrong path.

Any new word on those manual six port valves that someone
found and posted about here?

Brian Trubee


All,
Does Tracy's system use a fuel valve at all?  I am going to copy Tracy's system except I am going to use 2 submersible pumps in the left tank.  The only weakness that I see in Tracy's system is leaving the transfer pump on and pumping fuel overboard; this seems manageable with a timer.

Ken Powell


 
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