Hello Remi,
Thank you for your input which as usual, I appreciate.
I hadn't considered the effect of lower temperature at altitude but do
understand your reasoning albeit our temps are a far cry from yours. At
the moment, freezing level is above 10,000 ft. Regarding my fuel flow
meter, I do keep impeccable records of fuel used and my totalizer is
very accurate. I therefore have no reason to doubt the accuracy of the
flow meter.
In my quest for a better understanding of Bing carbs and there
idiosyncrasies, if you have any info available which you would be
prepared to share on your leaning system Remi, I would very much
appreciate same please.
Thanks again
Kingsley
On 12.12.19 8:11 pm, Remi Guerner wrote:
>
> Hello Kingsley,
> One reason for a higher fuel flow at altitude for the same MAP and RPM is that
your engine is developing more power. Taking your example, full throttle/20"
means you are at around 10000 ft. At this altitude, the outside temp is minus
4,5C (standard atmosphere) This is almost 20C less than at sea level. Then your
engine is developing 7% more power (293/273). The Rotax runs richer at altitude.
Based on my experience, this over rich mixture increases the fuel consumption
about 10% at 10000ft compared to low altitude at the same power. You say
your fuel flow is 40% higher: that is surprising and I assume your flow meter
is not accurate.
> I do not have any experience with the Hacman, but I have done some testing on
my 912ULS with my own mixture system (using an electric pump to suck pressure
out of the carb bowl vents). The system worked fine, was fail safe, but there
was no power gain at full throttle at altitude. This was disappointing and I
decided that the possible 10% fuel saving was not worth the additional
complexity.
>
> Remi
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