Today's Message Index:
----------------------
1. 08:48 AM - Disappointment in Rotax 9 series (rampil)
2. 09:22 AM - Re: Disappointment in Rotax 9 series (Jim Stewart)
3. 11:26 AM - Re: Disappointment in Rotax 9 series (Duncan & Ami McFadyean)
4. 12:37 PM - Re: Disappointment in Rotax 9 series (rampil)
5. 01:29 PM - Re: Disappointment in Rotax 9 series (Ivan)
6. 01:46 PM - Re: Disappointment in Rotax 9 series (Gilles Thesee)
7. 07:38 PM - Re: Disappointment in Rotax 9 series (rampil)
Message 1
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| Subject: | Disappointment in Rotax 9 series |
Hi All,
I have been a big fan of my 912uls since I started flying with it three
years ago. Part of the reason was the modern carb design in the Bing 64
with automatic (at least partial compensation for altitude in the) mixture.
All their advertising states this.
Well, unless someone can prove the following data wrong now, this
Altitude compensation is a complete crock. I really hope someone
has some data to prove this wrong.
I just happened upon the new Katana DA20-100 POH with official
performance charts of the certificated 912 and 912S engines. The AC
also has a Hoffman CS 2 blade prop. The charts clearly show
progressive increase in fuel flow with altitude at a set %max power.
This is of course the exact opposite of Lycomings and Continentals
and the Rotax/Bing claims.
Can someone please show me how this interpretation is wrong (no
handwaving please, just documented facts).
Maybe the GreenSky HAC or real fuel injection is the way to go!
I attach some charts which show the data
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=163160#163160
Attachments:
http://forums.matronics.com//files/912s_range_katanada20_100_187.png
http://forums.matronics.com//files/912s_performance_526.png
Message 2
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| Subject: | Re: Disappointment in Rotax 9 series |
rampil wrote:
>
>Hi All,
>
>I have been a big fan of my 912uls since I started flying with it three
>years ago. Part of the reason was the modern carb design in the Bing 64
>with automatic (at least partial compensation for altitude in the) mixture.
>All their advertising states this.
>
>Well, unless someone can prove the following data wrong now, this
>Altitude compensation is a complete crock. I really hope someone
>has some data to prove this wrong.
>
>I just happened upon the new Katana DA20-100 POH with official
>performance charts of the certificated 912 and 912S engines. The AC
>also has a Hoffman CS 2 blade prop. The charts clearly show
>progressive increase in fuel flow with altitude at a set %max power.
>This is of course the exact opposite of Lycomings and Continentals
>and the Rotax/Bing claims.
>
>Can someone please show me how this interpretation is wrong (no
>handwaving please, just documented facts).
>
Are you sure you have the right charts? The second chart
shows a range of 1900 - 2380 RPM which seems unlikely
for a 912.
Message 3
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| Subject: | Re: Disappointment in Rotax 9 series |
As part of some recent testing of a different propeller, a full power climb
from 2500' to 6500'+ showed constant RPM and EGTs all the way.
Fuel flow dropped steadily from 4.0 Imp GPH to 3.7 Imp GPH.
This suggests to me that the mixture was altitude compensating between those
altitudes. The reduction in fuel flow was consistent with a reduction in
engine power resulting from the lowering air density; not to be confused
with mixture.
But this was with a constant throttle opening (WOT), whereas the DA20
figures are for increasing throttle opening, necessary to maintain the
stated power level at the different altitudes.
Duncan McF.
----- Original Message -----
From: "rampil" <ira.rampil@gmail.com>
Sent: Saturday, February 09, 2008 4:46 PM
Subject: RotaxEngines-List: Disappointment in Rotax 9 series
>
> Hi All,
>
> I have been a big fan of my 912uls since I started flying with it three
> years ago. Part of the reason was the modern carb design in the Bing 64
> with automatic (at least partial compensation for altitude in the)
> mixture.
> All their advertising states this.
>
> Well, unless someone can prove the following data wrong now, this
> Altitude compensation is a complete crock. I really hope someone
> has some data to prove this wrong.
>
> I just happened upon the new Katana DA20-100 POH with official
> performance charts of the certificated 912 and 912S engines. The AC
> also has a Hoffman CS 2 blade prop. The charts clearly show
> progressive increase in fuel flow with altitude at a set %max power.
> This is of course the exact opposite of Lycomings and Continentals
> and the Rotax/Bing claims.
>
> Can someone please show me how this interpretation is wrong (no
> handwaving please, just documented facts).
>
> Maybe the GreenSky HAC or real fuel injection is the way to go!
>
> I attach some charts which show the data
>
> --------
> Ira N224XS
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=163160#163160
>
>
> Attachments:
>
> http://forums.matronics.com//files/912s_range_katanada20_100_187.png
> http://forums.matronics.com//files/912s_performance_526.png
>
>
>
Message 4
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| Subject: | Re: Disappointment in Rotax 9 series |
Followup-
JStewart: Think prop rpm, not engine RPM
NB: The data I appended was for the DV-20-100, not the DA-20
engine is the rotax 912S3
Just off the phone with Bud Yerly about this. He recounted a flight test
recently with no measured fuel flow, but with EGT declines with altitude.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=163184#163184
Message 5
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| Subject: | Re: Disappointment in Rotax 9 series |
Hi
The best "factual" data is what I have as my experience. I have owned a
912UL for about 4 years and definitely it does not have an altitude
compensating carburetor. As I go up in altitude I must allow for
increased fuel usage. As I go from 2000 ft to 9500 ft I increase my fuel
consumption by 20%. This makes sense to me since I am burning richer as
I go up in altitude. The new LSA's have the Bing compensating
carburetor and thus no mixture control.
My Jabiru engine has the Bing compensating carburetor. As I go up in
altitude I dont see much change in my EGT because in stead of the engine
running richer, the carburetor compensates to keep the mixture the same
as evidenced by a contant EGT. So I know for a fact that the Bing
compensating carburetor works well as stated. I dont know why Rotax
states the fuel cosumption is increasing with altitude. My engine does
the opposite and I run most efficiently at high altitude on my cross
countries.
Hope this helps. I have not been pleased with Rotax support as a whole.
Certainly there have been so many service bulletins out regarding the
912 that I almost wish I had my old 582 back.
Ivan
----- Original Message -----
From: "rampil" <ira.rampil@gmail.com>
Sent: Saturday, February 09, 2008 9:46 AM
Subject: RotaxEngines-List: Disappointment in Rotax 9 series
<ira.rampil@gmail.com>
>
> Hi All,
>
> I have been a big fan of my 912uls since I started flying with it
three
> years ago. Part of the reason was the modern carb design in the Bing
64
> with automatic (at least partial compensation for altitude in the)
mixture.
> All their advertising states this.
>
> Well, unless someone can prove the following data wrong now, this
> Altitude compensation is a complete crock. I really hope someone
> has some data to prove this wrong.
>
> I just happened upon the new Katana DA20-100 POH with official
> performance charts of the certificated 912 and 912S engines. The AC
> also has a Hoffman CS 2 blade prop. The charts clearly show
> progressive increase in fuel flow with altitude at a set %max power.
> This is of course the exact opposite of Lycomings and Continentals
> and the Rotax/Bing claims.
>
> Can someone please show me how this interpretation is wrong (no
> handwaving please, just documented facts).
>
> Maybe the GreenSky HAC or real fuel injection is the way to go!
>
> I attach some charts which show the data
>
> --------
> Ira N224XS
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=163160#163160
>
>
>
>
> Attachments:
>
> http://forums.matronics.com//files/912s_range_katanada20_100_187.png
> http://forums.matronics.com//files/912s_performance_526.png
>
>
>
>
>
>
>
>
>
>
>
Message 6
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| Subject: | Re: Disappointment in Rotax 9 series |
Ivan a crit :
> I have owned a 912UL for about 4 years and definitely it does not have
> an altitude compensating carburetor. As I go up in altitude I must
> allow for increased fuel usage. As I go from 2000 ft to 9500 ft I
> increase my fuel consumption by 20%. This makes sense to me since I
> am burning richer as I go up in altitude. The new LSA's have the Bing
> compensating carburetor and thus no mixture control.
>
> My Jabiru engine has the Bing compensating carburetor. As I go up in
> altitude I dont see much change in my EGT because in stead of the
> engine running richer, the carburetor compensates to keep the mixture
> the same as evidenced by a contant EGT. So I know for a fact that the
> Bing compensating carburetor works well as stated. I dont know why
> Rotax states the fuel cosumption is increasing with altitude. My
> engine does the opposite and I run most efficiently at high altitude
> on my cross countries.
>
Ivan,
Would you care to elaborate on the "compensating" and "non compensating"
carbs ?
As far as I could see, there is no particular difference between the
Bings 64 on the Rotax, and the Bing 64 on the Jabiru. Also, except for
the particular engine jetting, there is no apparent technical difference
between the carbs in each engine documentation : the Jabiru manual shows
the same picture as the Rotax.
In my opinion, the Bing carb provide *some degree* of altitude
compensation due to the constant vacuum design.
Best regards,
--
Gilles
http://contrails.free.fr
Message 7
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| Subject: | Re: Disappointment in Rotax 9 series |
Hi Gilles,
I think you are an experienced thoughtful guy, but what does it mean
to have an opinion on these carburetors . On the other hand, what you told Ivan
is absolutely
true from my hands on experience with both engines,
We are not talking about health food nonsense or placebo. We must talk
engineering, these are deterministic systems, they either work
or they do not work.
The DATA says they do not work, in fact, they perform WORSE
than just leaving full rich on a Lycoming.
I may well be wrong due to lack of sufficient data, but the DATA
so far says the 912S3 is CONTRACOMPENSATING.
Please explain to me my error. Opinions can not count
Has anyone performed actual, careful engine performance flight
test. I'd like to, but my new EFIS has the output of my FloScan
bouncing all over creation to the point where it is unusable.
Does anyone have DATA to share?
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=163233#163233
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