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Re: REFLECTOR: fuel system

Subject: fuel system


  Do you think your fuel flow meter might be causing you some trouble with
air bubbles?  Where else could we pick up air in this system?  Will your
system flow evenly from both main tanks to your sump?

  My sump tank is tucked up tight against the spar so there's a little room
under it for some fuel line and part of one fuel pump, the other pump is
right next to it flat on the fuselage bottom.  One pump is a Subaru pump the
other is out of a Mercedes, both pumps have a small screen filter in front
them and the "parts guy" said both of these pumps were pretty bullet-proof.

Since my pumps are both lower than the delivery line from my sump tank I'm
thinking that I should not have any priming problems.

One item on my pre-flight is to take a fuel sample to check for water in my
fuel so I'm not too concerned about agitating water back into the fuel by
where I have my return line coming back to the sump.

Do you use the aluminum vent manifold from the factory?  I have a 3/8" line
to the sump, a 1/4" line from each main tank and a 3/8" vent line to my
scoop going to this manifold.

I'm wiring my pumps to my main buss, then to my panel.  I would like direct
control of the pumps, not the computer.  I don't think I'll use both pumps
except for take-off and landing and the only time we'll be turning under
3800 RPM is during taxi.  If this turns out to be a problem, having too much
pressure during taxi, I like your idea of making a resistor circuit to lower
pump output.

My "Mustang" scoop where my vent line comes out is well forward of my
exhaust so I don't foresee any problems with over filling the fuel tanks and
having some vent out there.  I've incorporated an exhaust augmentor in my
lower cowl so the exhaust sweeps as far back as possible.  I also like your
idea to bleed a small quantity of fuel back to the sump tank before the
pressure regulator to nuturalize pressure after shut-down to prevent priming
problems -- thanks for the tip.

 How did you design your throttle quadrant? I scrapped all the linkage that
was there and built an aluminum bracket for my cable end to fit into from
there  I built an aluminum arm that actuates the butterfly in the throttle
body.  This way I eliminate all the springs that want to return the throttle
to idle.


PS sorry it takes so long for me to respond I'am your basic two-finger