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

Thanks Russell.
I need to implement some form of cam /microswitch to manage the pumps as I do not want to have
some situation where the pumps are on but the sump is not being fead.
I was going to vent the sump to the tanks and vent the tanks, this prevents any vapor accumulation
in the sump after initial fueling.
...Chrissi

 
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