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Re: Europa-List: Rotax fuel flow detection

Subject: Re: Europa-List: Rotax fuel flow detection
From: Juergen Buschmann <jubu@onlinehome.de>
Date: Wed, 27 Oct 2010 22:15:20
I will too install a fuel computer this winter to my 912s.
In the manual of my FC1 Flybox is a schematic I will post here
and I cant see why it shoud not work.
Even measuring the fow of only one carb it should be no problem to find 
the right k-faktor setting.


Am 23.10.2010 10:44, schrieb Guerner Remi:
> Svein,
>
> I basically agree with what you wrote. However  my proposed schematic 
> is very close to the one recommanded (and optionally  supplied) by  
> Rotax in the 912 Install Manual (see attached). This arrangement works 
> on most LSAs so I do not see why it would not work with the addition 
> of the fuel flow sensor as propsed.
>
> Regards
> Remi Guerner
>
>
> <<<<<<At first sight, your proposal may look like the obvious 
> solution.  With
> respect, however, I think it is not to be recommended for 912ULS
> installations (I do not know enough about 914 to comment on that engine).
>
> Contrary to what seems to be a common assumption, the return flow through
> the restrictor is not insignificant - it is roughly 10 litres per hour 
> (i.e.
> roughly half of the net cruise consumption, or roughly 1/3 of the fuel 
> going
> to the engine is flowing back to the tank).  The reason for this 
> relatively
> high surplus circulation is of course to reduce the time the fuel is 
> exposed
> to heat before it reaches the carbs, by increasing the flow velocity 
> through
> the fuel line.  According to the build manual, the return line 
> branches off
> at the point farthest from the pump, just before the left side carb
> (assuming the fuel line goes from the pump to the right side of the 
> engine
> with a short branch off to the right carb, and from there across the 
> back of
> the engine to the left carb).
>
> Moving the return line branch-off upstream (closer to the pump) increases
> the risk of vapour forming in the fuel lines downstream from this 
> branch-off
> point.  By how much, I do not know, but maybe it is critical under
> unfavourable circumstances.  "Maybe's" under the cowling are not nice 
> - - -
> - - .>>>>>>>>>
>
>



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