On 07/02/2010 03:57 PM, rparigoris wrote:
> If you were to have such a circuit, you would want to have it turn on
> second pump when it falls below ~ 2 PSI differential pressure (fuel
> pressure going to carb less the airbox pressure).
I agree you should have a differential fuel pressure switch. The Rotax
maintains a specific fuel pressure OVER the airbox pressure (which
varies with power setting and altitude).
> not be the thing to do if you have parallel pumps because you can
> blow over the ~ 5 PSI differential.
I have the serial pump layout, but with a full tank and both fuel pumps
on, the differential pressure raises to 6 psi while the engine is
running on low power. I was concerned that this higher fuel pressure
would choke the engine during the approach, when both fuel pumps are on
and the power setting is low, but I have not experienced any problems
with it.
Yet I would like to know whether this is normal. During flight, with one
pump on, the differential pressure is always around 4.5, regardless of
power setting. Interestingly, the fuel pump connected to the Andair
gascolator provides a lower pressure than the fuel pump connected to the
disposable fuel filter.
Frans
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