Ed,

The reasons for not wanting to pressurize the sump tank are
1) don't want a pressurized tank inside the aircraft
2) making a leak proof fiberglass tank is difficult and
don't want to make it harder, although it shouldn't leak
under any contition - just don't like the idea to pressurize
it as of now.
3) two more parts to go bad.
4) more cost

The sight glass is for checking condition of screen filter.

If I could figure out a good way to put the efi pumps inside
the sump tank and get a good seal, that would be my
preferred way to go.  I could use a barb fitting to go thru
the tank for the pressure line, but still need a large
removeable accesss hole to install and service the pumps.
Auto pumps go thru the top of the tank and have little
pressure to seal against (usually a slight vacuum).  My sump
could be thought of as the bottom of the tank - any leak
would empty the main tanks.  Any leaks that develope in time
should be small and the smell would let it be known due to
the sump location.  Maybe I should go with an aluminum sump
tank and use a good sealant for access ports.

I tested the flow of the fuel line before I closed the
strakes and believe the flow at worst condition of less than
2 gallons (about and inch of water in the tank) and think
the flow rate was about 12 gph.  This was with no filter
except the coarse screen in the tank.  So 2 x this would
give 24gph and one would never want to take off with only 2
gal. in tanks.   From this test I felt that no extra pump
would be needed to keep down vapor formation.  Would the
filters you are talking about work in this installation of a
gravity feed?  They are neat.

Wendell (still figuring)

I used the coarse filter only before the EFI pumps and the
facet pump is between the tanks and the coarse filter.
Unless the coarse filter is  filled with debris there is
negligible pressure drop caused by this filter.  My EFI
filters on the other hand are after the pumps.  But, you
are quite right, you don't want any drops in line pressure
that can lead to vapor lock.

Don't know why you don't want to pressurize the sump.  The
facet pump only puts out approx 4-6 psi and I can attest,
that additional pressure, can squelch vapor locks between
the facet pump and your EFI pumps.  It also helps
compensate for the fact that the EFI pumps (as do any
pumps)   lower the line pressure at their entrance.
Maintaining pressure in your fuel lines is one of the
fundamental needs especially when the lines are exposed to
heat sources.

The recent advent of "Returnless" fuel lines in automobiles
relies on managing line pressure to prevent vapor lock.
Tracy Crook has implemented such a system in his 20B
powered RV-8 and at least on the ground (he has not flown
yet), it works fine.  Any system that keeps line pressure
up above a certain point will work, any that permit it to
drop below a crucial level at any point will have problems.

I agree with Al, that from a vapor lock safety standpoint
having wet pumps in the tanks and returning fuel to the
larger tanks (as a heat sink), have proven to the about the
best approach.  In my case, I did not want high pressure
lines in the cockpit, nor the complexity of switching both
main and return lines when switching tanks (there are other
alternates which do not require switching between tanks -
line intra tank transfers, etc).  Like anything else there
are trade offs to any decision.

This is certainly one of the most (if not the most) crucial
subsystems in your engine installation along with ignition.
Taking line pressure measurements as Al Wick suggests is
certainly a good idea - then as, Al points out, you are
dealing with a known rather than guessing and hoping.

Ed


 ----- Original Message -----  From: Wendell Voto
 To: Rotary motors in aircraft
 Sent: Sunday, September 09, 2007 9:44 PM
 Subject: [FlyRotary] Re: need help



 Ed,

 You stated that you use Facet pumps, I suppose these are
before the in-line filter. My concern about using the
filters before the efi fuel pump is that there would be
more flow restriction. Since I will be using gravity fed
sump tank (5-6 inch elevation difference and I don't want
to pressurize the sump tank), that vaporization could occur
; hence I am still thinking of a large surface screen in
the sump tank (already have screen wire over the strake
tank outlets) to catch small stuff that could shorten pump
life, not necessarily plug up the pump. MSD claims to be
able to handle small particles better than the competition.
Thinking also of putting in a sight glass (Plexiglas) to
observe tank behavior and screen condition. Can Plexiglas
hold up to auto gas?
 Oh yes, the sump tank will have a water catch sub-sump.

 Wendell (hope I'm making sense)

   I have opened up my coarse filter 6 times in 10 years.
First time had some small fragments of sealant used to
close the tank.  The next 5 times nothing.  Of course, a
lot will depend on type of tank and quality of fuel going
into the tanks.

   I replace the EFI filters at each conditional
inspection, cut the old ones open and have never found
anything in them either.  But, I do use 100LL aircraft
quality gasoline - almost exclusively..

   ED
     ----- Original Message -----      From: Wendell Voto
     To: Rotary motors in aircraft
     Sent: Sunday, September 09, 2007 4:00 PM
     Subject: [FlyRotary] Re: need help


     Thanks Ed,

     How often do you have to clean the filter?

     Wendell



       I have a fine wire mesh filter in an aluminum
housing with An-6 fittings on each end just before the fuel
enters my header tank..  You can unscrew one end to clean
the mesh.  However, been too long ago and I find I never
logged the part number on my fuel data sheet.

       But, here are the specific part numbers I use for
the EFI filters

       Fuel Filters: OEM Auto Fuel Injector Fuel Filters
(Two in Parallel)

       Type: AC GF - 481 Pkg: 25056052 OEM:25055129 (or
equivalent)

       Fittings: 3/8 Saginaw to AN6 Adapter, "O" ring
required



       Ed

         ----- Original Message -----          From: Wendell Voto
         To: Rotary motors in aircraft
         Sent: Saturday, September 08, 2007 10:18 PM
         Subject: [FlyRotary] Re: need help



           Thanks Rob and Ed for the replys on the MSD
fuel pumps.

           Now;  what kind of filter do you have ahead of
the pump?  I'm thinking of using some fine mesh screen to
make a filter inside the sump tank.  It will be hard to
service but believe that one will prolong pump life and
possibly. stop a particle that could interupt fuel flow.
What size mesh is recommended?

           Wendell


           I have been using the MSD 2225 for about 20
hour with no problem so far. Plenty of fuel pressure. Only
problem is that it is not threaded so I had to use the
barbed nipples that come with the pump. How bad can that
be?

           Robert Bollinger
           FM1099 MUM
           Fairfield IA 52557
           (641)472-7000 ex2068
           (641)919-3213 cell
           rob@mum.edu

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