I have a question for people with electronic fuel injection systems. My
question involves the tank setup and return lines. On a Cozy with a 20b.
I have a sump tank and I planned on having check valves between the wing
tanks and the back seat sump tank. ( I am using Infinity retracts ) I'm
not
using a tank selector valve. Only a fuel system on/off valve. I want it
simple yet right. I have 1/2" stainless tubing between the tanks and
1/2"
outlet from the sump. Now I'm concerned about the return line from the
Fuel
Injection. Will the pressure of the heated return lines keep the check
valves from allowing more fuel into the sump? I plan on a vented system in
all tanks but then worry that any pressure could push fuel out of the sump
vent line. I planned on having positive air pressure on the vent lines
during flight by facing the outlets into the wind or "jetstream"
I've got notes from other past questions on this group that suggest the
check valves but I'm not sure they are using EFI and I wonder where they
are
returning the fuel.
Rick Irwin
My opinion is that the deciding factor would be the pressure from the
ram-air vents. The fuel injection system will be returning less fuel
than it takes from the sump tank. The overall pressure will be whatever
the ram air supplies to the tanks. If the pressure to all the tanks is
the same, in theory you should have no problem. -In theory.
I copied Tracy Crook's setup- all fuel to the engine taken from and
returned to the right tank, and a facet pump transfers fuel from the
left to the right pump. I elected to heed the age-old advise- keep it
simple.
That's my opinion, but I am a product of public education, so follow it
at your peril.
Brian Trubee
Be very very very careful about using dynamic pressure vents. Vents facing forward.
At speed, dynamic pressure alone can empty a tank in minutes. Use something
that is proven to work. Follow the Cozy plans exactly. I would be wary of
using one way valves.
There are dozens of pit falls to fuel systems. Improperly
designed fuel systems are a leading cause of crashes.
If you use an Andair valve make sure it is in a place that
cannot inadvertently be switched by objects in the cockpit
such as knees and elbows.
--
Paul Lamar ...No rotor no motor.
I have dual fuel pumps inside a small 1 gallon "sump", fuel return to sump, sump mounted very low.
L-R-OFF fuel selector per Long-EZ plans (Cozy is probably similar), selected main drains to sump.
There are no issues with fuel heating. The sump must be vented, but cannot receive ram pressure
higher than what the main tank vents see.
Very simple.
Perry
http://www.mickaircraft.com/duckt.htm
Paul,
My SeaWind is set up identically to what Perry described with cable
activated large mechanical valves draining either the right or left wing
tank into a three gallon low sump tank. A low fuel warning sensor is
set into the sump tank halfway up as to serve as an audible warning in
case the wing tanks were not selected or flowing.
All check valves have gone into the `will not use` pile.
Check valves in fuel use applications are only good when they have
significant pressure on them to seal and significant pressure to
overcome the spring in operation. They do cause a restriction in flow
naturally and in running multiple pumps in parallel they are required.
However in gravity flow locations they tend to seep, especially when a
speck of grit is on the seal. Electric solenoids? IMHO OK only for non
critical applications providing the cut off mechanism in cross feeding
between the starboard and port wing tanks. Most airplanes don`t need
this feature but Seaplanes need to sometimes move fuel while on water
from one side to other to trim the plane for take-off. I might add
that quite a few SeaWinds to date have been downed by fuel system
related troubles. Solenoids can fail from dirt or electrical problems.
Doug in Japan
How was your trip to Germany?
Did you make it down to the Wankel Museum?
Paul Lamar ...No rotor no motor.
Paul,
Business went well at the inverter factory in Kassel but last Saturday
was an extended holiday break and all staff with autos headed out of
town with their kids leaving me with the trains. Not as fast as Japan
but definitely more room. Nice. Next time the wankel museum perhaps.
I ended up touring the museum of natural history in Frankfurt featuring
dinosaurs, fossils, and stuffed animals. No reciprocating engines on
display there...YET.
Doug
The Europeans are becoming Americanized :)
For a true European experience you need to rent a car.
Next time you go I'll put you in touch with some of our
friends in Frankfurt. Just give me a bit more warning so
I can check it out with them in advance.
Paul Lamar ...No rotor no motor.
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