>I am building an RV9-A and am planning to use a 13B engine with Tracy
Crook's EC2 and EFI system.
Can anyone recommend an in-tank electric fuel pump meeting the pressure
requirements for an EFI? It should fit inside the tank of the RV9. Would
prefer an automotive solution as they are both relatively low cost and
alcohol proof. Ideally the pump should have a check valve built in so
that no reverse flow of fuel can occur. Reason for this is explained
below.
I am also looking for alcohol and gasoline proof electrically controlled
"lock out" valves.
*System Description*
The fuel system I am planning to use has a fuel pump in, or near, each
tank. Pressurizing the fuel supply lines to EFI required levels (3 to 4
bar?) prevents vapor lock. With the inlet of the pump below the level of
the fuel in the tank, there is (almost?) never any time that the fuel
pressure is below ambient atmospheric, i.e., is not being sucked out of
the tank. Each tank has a dedicated return fuel line with a "lock-out"
valve forward of, or at least close to, the firewall. In operation, an
electrical switch on or near the instrument panel selects which tank to
draw fuel from by turning on the appropriate pump and opening the fuel
return line for that tank by energizing the "lock-out" valve. Fuel is
prevented from returning to the wrong tank by the closed "lock-out"
valve. This plan avoids the expense of a six way valve, and the
convoluted plumbing with all the extra connections that offer points of
failure.
*Alcohol requirement*: I want to use mogas. Colorado, like many western
states, recently passed a law requiring all mogas (except 91 octane
premium) to be oxygenated with ethanol, up to 10%. Probably the amount
of ethanol will be increased in years to come.
Thanks in advance,
Doc
Just about any modern in the tank automotive pump will work
as most modern EFI system require around 50 psi.
Pick one from a car that has at least 250 HP.
They do have one way valves but test it before you install it.
Paul Lamar ...No rotor no motor.
The two cautions that I would have with your system are:
1. With pump failure, you are limited to whatever fuel is left in the
opposite tank with no chance of recovery of the fuel remaining in the
first
tank.
2. With the failure of a lockout valve, any consequences would depend on
the
design of the fuel pressure regulation scheme.
I personally have 2 of Tracy's fuel pumps with built in check valves
mounted
in parallel downstream of a 6 port duplex valve. Plan is for both pumps on
for takeoff and landing and single pump on for the rest of the flight with
the other pump available for back up at any time.
Dean Van Winkle
RV-9A 13B NA, Mistral Intake, RD1B, EC2, EM2
Dean,
Thanks for the input.
Point 1 (pump failure) is well taken and I am concerned about it. Have you
had any vapor lock problems with your setup? What kind of summer
temperatures have you flown in? I have family in AZ and the OAT can exceed
100F in the summer.
Point 2: I have been thinking about this, and perhaps have found a better
way by using the 4 way valve I already have (part of the fuselage kit) to
switch the return lines to the proper tank. I would mount two microswitches
on the valve to control the tank pumps, so only one control to change tanks.
This might be less weight than the lockout valves. However it does not
address point 1. Hmmm.
Doc
Here are some old 3D's on the subject.
Paul Lamar
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