I have read in the 915iS Installation Manual that the Ambient Air Pressure and Temperature Sensors in a cowled engine installation must be located in a position of ambient air and must be located in a ram air free positon.

It was pointed out to me by an engineer that my AAPTS sensors are not in a ram air free position.  What down sides or side effects would this have please on the running of the engine?  Any short or potential long term effects or fuel economy effects perhaps?

Many thanks.



7804_1_AAPTS Sensors.jpg (You do not have access to download this file.)
  • Re: AAPTS Sensors / Position

    by » 4 years ago

    The AAPTS is the sensor to the outside world for the engine.

    It should be located in the same airflow that the air filter sees.

    Normally this is within the engine cowling and in the vicinity of the Air filter.

    It should not be projecting outside of the cowling or far removed from the air filter.

    You want to be measuring what the engine(Air Filter) is seeing, not the wing.

    However, if your induction system consists of a closed air scoop/duct system that channels ram air from the airstream directly to the air filter, then the AAPTS should be installed to measure the air within this duct. Technically it is Ram AIr but it is the ambient air the engine is operating in.

    The ECU uses this Ambient Air Pressure(APP) and Temperature(AAT) information along with the Manifold Air Temperature(MAT) and Pressure(MAP) to control the fuel flow.

    If the sensors are measuring values wildly different from what the engine is actually seeing, your fuel mixture will be affected.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

    Thank you said by: Paul Setterfield

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