Hi Ian
My statement was based on Europas comment when they
implimented series with bypass and offering a differential gauge that
having parallel pumps running can overwhelm fuel pressure regulators
ability to get fuel out of its exiting orifice and blow above high side of
5PSI. John Hurst also mentioned parallel with both pumps running would go
above 5 PSI. (I purchased my UMA gauge from him). Through the years I
either read or talked to folks that the same was mentioned. Some folks
said they ran 2 parallel pumps for take off and landings without
problems. Running parallel increases flow when second pump is turned on
but pressure is about the same. Running second pump in series increases
flow only a slight bit but can increase pressure. I tested my series with
bypassset up on bench and when challenged with restriction on
intake or output second pump helps a lot:
http://contrails.free.fr/engine_914_fuel_syst_test_en.php
Ron
Parigoris
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