Ron
Where does the information that the parallel system blows over 2.8psi come
from. From memory one of the books says it should be 1.8psi from either
pump and 2.8 with them both on.
This is exactly what my IES tells me is happening in G-IANI. We use this
fact to check that both filters are not blocked at every engine start.
Ian Rickard G-IANI XS Trigear, 300hours
Europa Club Mods Specialist
e-mail g-iani@ntlworld.com
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of
rparigor@suffolk.lib.ny.us
Sent: 06 July 2010 20:32
Subject: Re: Europa-List: Re: Pierburg Output Fuel Pressure
Hi Frans
Just a few ideas:
Differential pressure gauge may not be speaking absolute truth
The fuel pressure regulator is adjustable, you could lower a pound
You may have more of a restriction on the return line than is desirable,
make sure fittings you are using are of large bore varient. supplied with my
kit were both large and smaller bore (more restricting). also look for kinks
or pinches. Rotax tells you max. restriction they want, worth measuring.
Measure and or fix restriction before you adjust regulator.
Fuel pressure needs to be higher than airbox pressure or it won't flow into
carb bowl. Too high and it could overcome needle valve and leak. That said
there are plenty of 914s flying with parallel fuel systems that blow way
higher than 5 PSI and pilots sday seems fine. 6 PSI is not very high, but if
it were i I would get it down a little if i could. Perhaps you can check
gauge/sender calibration?
Ron P.
>
> 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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