By way of comparison for a normally aspirated engine (912S), in a full power
climb from 2000' to 6650' (at OAT +5C @ 2000' and QNH 1005), fuel flow
dropped from 4.0 to 3.7 imp.GPH.
I've not worked out the percentage power loss due to air density, but would
guess that this was more than the % drop in fuel flow. Engine speed was a
constant 4800rpm throughout. No EGT data available, which would have shown
any richening of the mixture with altitude (as I recall, EGT does usually
get less with altitude on this engine, but not greatly).
Duncan McF.
----- Original Message -----
From: "Kingsley Hurst" <hurstkr@redzone.com.au>
Sent: Saturday, November 14, 2009 10:35 AM
Subject: Re: Europa-List: Re: does rotax need egt?
>
> <hurstkr@redzone.com.au>
>
>> Attachments:
>>
>> http://forums.matronics.com//files/rotax_efficiency_125.pdf
>
> Hello Ira,
>
> Thank you for posting those figures . . . interesting indeed. 60%
> increase
> in fuel consumption flying at 9,000 ft as opposed to 3,000ft while TAS
> increases 33%.
>
> I note the increase in fuel consumption is almost linear from 3K to 7K ft
> while the increase between 7K and 9K is double that between 5K & 7K. I
> imagine 22.6" MP at 9K would be wide open throttle so I'm wondering if
> this
> kick in the consumption is because of power jets coming into play.
> Regardless, there is nothing that can be done about it with things as they
> are so I can certainly understand your desire to install a mixture
> control.
> I look forward to hearing how you accomplish this.
>
> Sorry I am unable to supply any comparative data yet.
>
> BTW, your MPG figures appear to actually be NMPG so your actual MPG is
> still
> way ahead of any motor vehicle travelling at 146 MPH. Realizing that may
> make you feel better No?
>
> Somewhere I saw once that Rotax actually do have true altitude
> compensating
> carburettors but for the life of me I cannot recall where I saw that.
>
> Cheers
> Kingsley
>
>
>
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