All,
I think Rotax may do a mixture mod for the 912's Bings - talk to Skydrive.
Dave Simpson
-----Original Message-----
From: Wilksch Airmotive <mark@wilksch.com>
Date: 22 August 1999 11:28
Subject: Re: Flying: Fuel consumption in 'Classic' with Rotax
912.
>Dear Barry
>
>The increased fuel flow with altitude is due to the carbs going rich.
>Despite the mis-information to the contrary, the Bing constant vacuum
carbin
>the 912 does not compensate for altitude. The reason the 912 does not need
>a mixture control is that it is liquid cooled with small cylinders and can
>run at both sides of the stoiciametric AFR without detonation ie it runs
>relatively lean at SL and enriches with altitude. Eventually this shows up
>as high fuel consumption.
>
>The frequent claims that the CV carbs are "altitude compensating" are
untrue
>and rather irritating. Why should a CV carb know more about density than
>any other carb (it has no aneroide) and no other special magic. Only an
>aneroide can feel the density altitude (so can a turbocharger since it
feels
>absolute pressure ratio) but that's another story.
>
>Hope this is of some interet to you.
>
>Regards.............MARK WILKSCH
>
>
>-----Original Message-----
From: Tennant <Tennant@t-online.de>
>Date: Thursday, August 19, 1999 07:56
>Subject: Re: Flying: Fuel consumption in 'Classic' with Rotax
>912.
>
>
>Hi Alan
>You have posed a very complex question.
>I have faxed you a copy of the Power settings for the Katana which shows
>some
>interesting traits of the Rotax.
>
>One of the most interesting things is that the relationship between power %
>and
>fuel flow. For example 75% at 4000 ft will use only 16,3 L/hr but at 6000
ft
>it
>will use 19,3 L/hr.
>
>I think that the guys with the VP props will all confirm that the RPM does
>not
>seem to effect fuel cosumption or speed nearly as much as the throttle
>setting.
>
>Also, dont worry too much about reving the rotax, it prefers it and in the
>Katana is recomended to run at max continuous rpm always!
>
>Best regards
>
>Barry
>
>alan.d.stewart@bt.com schrieb:
>>
>> Does anyone know the value of engine RPM which would correspond to 75 %
>> power in the standard 912 UL fitted to the Europa ?
>>
>> At the current prop. setting my engine RPM reads just over 5000 static,
>4820
>> in the climb, and circa 5700 firewalled, S & L. (Figures accurately
>measured
>> on Rotax Flydat). I do not have the cool air, plenum box mod.
>>
>> The reason for my question....
>>
>> http://www.zenithair.com/kit-data/zac-rtx912.html
>>
>> 'Fuel burn @ 75%: 4.5 US gph'
>>
>> This corresponds to 3.75 Imp gal/hr or 17 litre/hr.
>>
>> My long term actuals, range from 15 - 17.8 litre/hr at cruise RPM of
>around
>> 4800 - 5200, and I was wondering how closely this correlated with Rotax'
>> published figures.
>>
>> It would make sense if 5100 RPM corresponded to approximately 75% power,
>as
>> this would tie in with the published figures.
>>
>> I could look at some of the data in the engine manual for this, but was
>> wondering what results other people have been getting ?
>>
>> Many of you appear to have quoted figures of around 11 - 12 litre hour
>which
>> I could not achieve without throttling back to much lower RPM's.
>>
>> I'm fortunate to have a large (early design) 84 litre tank in my a/c.
This
>> gives a safe maximum of around 70 litres useable in main or about 4 1/4
>> hours endurance at standard cruise (approximately 450 nautical miles).
>>
>> Alan Stewart
>> ab ASE - Advanced Systems Engineering
>> BT Adastral Park. Tel:- +44 (0) 1473 607571 / Fax:- 606845
>> mailto:alan.d.stewart@bt.com
>>
>
>
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