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Message
Yes,
its true Rusty. With both pumps on I show >80 gph going through the
return line. I put the fuel flow sensor in my return line for a few
reasons:
1) It
came with my engine monitor so needed to put this $250 sensor
somewhere
2)
Along with fuel pressure, it is a way to check and make sure the entire fuel
system is working. If a pumps starts to fail via low output or there is a
clog in the filter or elsewhere in the system it will manifest with decreased
flow but maybe not in the fuel pressure.
3) It
gives me a rough gauge of fuel consumption. For example, I know
that it reads 52 gal/hr at idle. In a high power climb it reads, say,
38gal/hr which means that I am burning something less that 14 gal/hr.
Keeping the throttle setting the same I can lean the mixture and watch the
return flow climb up to 44 or even 46 gal/hr (my fuel burn has now dropped to
about 6-8 gal/hr).
Of
note, these numbers are just rough estimates because the output of the pumps
changes pretty significantly with the pressure they are seeing. By making
adjustments to the fuel pressure regulator with the engine off I could get the
flow to drop to 20-30 gph by increasing the fuel pressure to 60psi. Since
my fuel pressure varies with MAP so will my baseline fuel
flow.
Also,
buss voltage changes the output of the pumps. By turning off the
alternator at idle the return flow with drop by about 5
gal/hr.
Yes, I
believe that we are well mixed. So much so that I have never sampled my
fuel for water. I am even thinking about removing the sample ports and
putting in low-drag plugs. Every bit helps :-)
Dave
Leonard (still waiting for a replacement oil cooler)
during his flight with Dave
Leonard, he personally observed 45 gallons per hour fuel return with one
of Tracy's pumps on and 80 gallons per hour with both pumps on!! Dave
has a flow meter on his return line.
Wow, is that true Dave? That seems high, but I
have no way of measuring it. I run both pumps all the time (aside from
testing them individually during preflight), so I guess my fuel stays
pretty well stirred :-)
Rusty (yes I know you don't need to run both all the
time)
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