REFLECTOR: Fuel flow - RG sump

[Al Gietzen]

While I had the fuel line open for servicing the filter; I made some
measurements of fuel flow yesterday to get a better handle on flow rate from
strake to sump.  The strakes had about 6 gals each side at the start.  I
first pumped fuel out of the sump with one of dual FI pumps (before the
pressure regulator, no back pressure).  Timed flow for 2 1/2 gals was 3
minutes, 15 seconds – which is a flow of 45 gph.  The sump low fuel level
light did not go on.

 

At first I thought, “Great, that’s a very good rate.”  But I now apologize
for my impatience because it could be that the sump level was slowly
dropping to the level of the float switch, and that over a longer period of
time the light may have come on.  However, estimating that there is ½ gal,
or less, above the low level switch, this would still indicate that the flow
rate from both strakes to the sump was about 35 gph, or better.  (Stock vent
system including sump vent, sump tank down close to fuselage bottom, 3/8”
lines from strakes.)

 

I then made the same measurement with both pumps on; and, as expected the
rate doubled.  The sump light came on about 15-20 seconds after starting the
pumps.  All I inferred from this was that the first test was probably close
to the upper limit – and I went on to other tasks.  My engine will never
burn more than 22-23 gph.  35 gph should be good to over 400 hp.

 

I was pleased to note that there was only a very small amount of what looked
like dirty lint in the filter after about 7 hours of engine operation –
first servicing from newly built strakes and sump.

 

FWIW,

 

Al 

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