John, As a matter of interest did you record air speed and ground speed for
these altitudes and rpm? David G-XSDJ
----- Original Message -----
From: John & Paddy Wigney <johnwigney@worldnet.att.net>
Subject: Europa-List: Bing carburettor, altitude compensation discussion
<johnwigney@worldnet.att.net>
>
> Perhaps I could add some of my observations to this discussion. I have
> recently done some checks at various altitudes and can report the
> following :-
>
> All results were done on the same flight and are at 5,500 rpm, at full
> throttle and the heights are pressure altitudes. The engine is a 912S
> and I have the data to prove that my fuel flow meter is accurate.
>
> 2,500 ft, OAT = 13 degC, 6.6 US gal/hr.
> 5,000 ft, OAT = 9.5 degC, 6.2 US gal/hr.
> 10,000 ft, OAT = 7 degC, 5.5 US gal/hr.
>
> I did not note the EGTs but will check these next time out.
>
> I do not have any technical info on the Bing carb but it appears to me
> that the fuel flow rate is certainly being adjusted with altitude. This
> is consistent with my understanding of how the similar SU carburettor
> works with the free floating piston and tapered needle being positioned
> according to the pressure in the carburettor throat. If the absolute
> pressure in the throat at full throttle is lower due to increased
> altitude/reduced density, the tapered needle will be lower in the jet
> and the fuel rate will decrease accordingly.
>
> Cheers, John
>
> N262WF, mono XS, 912S, Whirl Wind C/S prop, 220 hours
> Mooresville, North Carolina
>
>
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