Econ mode setting 912IS with airmaster constant speed prop

The engine is in ECO mode from 5500 RPM and below.

Anything over 5500 RPM is Power Mode and fuel consumption is increased.

Set your prop pitch so you get 5800 RPM, (Max for 5 min), for take-Off and climb performance (Power Mode), and then throttle back to 5500 and below to remain in ECO mode. 

As well as 5500rpm or below you need a Manifold pressure below 900mbar, 26"mercury. There is a graph of all of this in the Engine Operators manual under performance data.

I would suggest setting the Airmaster cruise to about 5200 rpm and 25" mercury of less, personal preference but peak Torque in the IS Sport is 5000 rpm, so this is where the engine has it's peak volumetric efficiency and operating near there is likely to get best mpg !

I have found 5000 rpm and 24" gives a good cruise. this results in 100kt IAS at 9500 ft. I can get better mileage at 70 kt and 4500 rpm and about 15" but it is just painfully slow....but I keep this up my sleeve for when I forgot to fill up and do not want to swim !!

Thanks Glenn,

That is very good and practical information.

Much appreciated

Hi all

Given we are discussing the fuel injected engine let us not forget that fuel flow is adjusted by the computer on an internal map.  Your operators manual has some valuable clues as to what ECO MODE is.  in it clearly stated is the fact that the computer will look for a lot of factors, MAP pressure and also throttle position.  If you are below the 97% throttle position it automatically will come into ECO MODE.  That said it then becomes very much about your RPM and MAP pressure as seen in the chart.  You should also look at where best torque of the engine is, that being 5200 RPM.  While we can get a lower fuel burn below 5200 you are also below your power curve.  This then becomes an issue as to prop loading and the Rotax does not respond well to overloading the prop.  I believe Glenn has good numbers but for me personally below 5000 starts to get too far below the power curve should I need to add power in a hurry.  Just my opinion.. 

Cheers

Thanks, that is interesting information, 5200 RPM and 25" looks like a practical setting for cruise. Looking forward to seeing what TAS I see at ISA +10 at 9500 ft.

Rgds

Glenn P