Posted for "Al Gietzen" <alventures@email.msn.com>:


  One last question came to mind
as I was imagining the fuel returning to the sump tank.  Is it normally a
large volume of fuel that returns to the tank, or just a trickle.  I ask
that because I need to consider how large of a sump tank to incorporate into
my fuselage.  Thanks again, Tracy.    Paul Conner

Paul;

The amount of fuel returning to the sump is the flow rate from the pump
minus the amount the engine is burning.  So if the pump is putting out 35
gph, and the engine is burning 15 gph you've got 25 gph going back to the
sump.  The amount returning to the sump is, of course, always less than what
is going out, so sizing the sump may be determined by other factors.  But
just from the recirculating issue, the larger the better because the fuel
returning has been warmed by the pumping and whatever heat is picked up in
the engine compartment.  I'd just guess that you'd like a sump tank of about
4-5 gallons +, or consider returning fuel to the main tank if that is
reasonable.

Best that the pump you chose doesn't pump more than about 1.5 times the max
burn rate that you can expect; at the pressure for your injectors, which
probably 40-45 psi.

Al