Chrissi wrote:

We've got two strake tanks feeding a large sump, 3-4 gal's worth. Was going to return fuel to the
sump. Seperate shutoff valves for L & R tanks (side by side levers). I can see Perry's paralel pumps,
we have two available as well as two pickups from the sump so that would work.
Any alarms going off yet?

zzz... Wha??.. . *yawn*  muttering... where's that snooze button...  :-)

More seriously, what is your planned normal operating mode with respect to the pumps?  Both on 100% of
the time?  I ask because the fuel heats as it *circulates* through the rail.  Fuel that is not injected
returns to the sump with heat picked up from the rail.  Just like the water cooling system, the faster
the fluid circulates, the more heat is transferred (although it is a non-linear relationship).

If both pumps are individually capable of supplying adequate fuel for full power max RPM operation, then
you can see where running both pumps all the time is going to maximize the heat transferred to the sump
(not really desirable).  In that case, I'd have a policy of running both pumps at those times where an
engine stumble would be really inconvenient, and run only one pump at all other times.  You could
alternate which pump is off in order to balance the wear & tear, or always turn the same pump off so
that it wears out first (maybe one's easier to replace).

Russell Kent

 
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