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Europa-List: Boiling fuel due to underpressure?

Subject: Europa-List: Boiling fuel due to underpressure?
From: Remi Guerner <air.guerner@orange.fr>
Date: Thu, 16 Oct 2008 21:46:59
Frans,


Have a look at the curve on paragraph 9.5 of the 914 Operator=92s Manual 
which shows the correlation between throttle position and airbox 
pressure (absolute pressure). This curve shows that airbox pressure 
increases from 45 percent throttle position and beyond . So as long as 
you are running beyond the 45 percent throttle position,  when you push 
the throttle forward you increase airbox pressure. This causes the fuel 
pressure regulator to increase the fuel pressure, and, as demonstrated 
before, the flow through the pump is reduced.


There is a common misconception that the turbo is providing boost beyond 
the 100 percent throttle position only. This is far from the truth. The 
airbox pressure curve shows that the turbo is boosting any time you are 
running beyond 45 percent throttle position. And this is at sea level. 
At altitude, the turbo is providing boost all the time, whatever the 
throttle position.


Remi 


[/quote:08514aa99f]

Somehow you make the assumption that giving more power causes somehow 
the regulator
to change its pressure setting?
I agree that the turbo changes the pressure somewhat if you get over the 
100% stop,
and then you may be right, the fuel pump needs to work harder. However, 
up
to the 100% level, the pressure in the airbox should hardly change. In 
this
range, the power lever should have no influence on the fuel pressure 
needed, and
hence not affect flow.


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