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  • Re: Rough running/High EGT in Cylinder 2

    by » 3 months ago


    Thanks very much Bill for explaining that the  timing of a spark(s) relative to TDC is of greater importance for maximum efficiency of combustion than the number of sparks, and because the ECU of the IS motor continuously electronically adjusts ignition timing, maximum efficiency can be attained with a single spark.  There is no additional efficiency produced when more than one plug fires each cycle if a single spark is optimally timed. 

    I have one further question for Bill;

    the faulty number 1 coil in my engine was causing cylinder 2 to have combustion every alternate cycle (when both Lane A and B were switched on) owing to lack of sufficient spark at 2B spark plug.  The EGT in this cylinder was observed on the Dynon Skyview to be approximately 200 F higher than the other cylinders (800 F cf 600 F) with the engine at 2000 rpm and both Lane A and B switched on.   What caused the EGT in cyclinder 2 to be higher when combustion was occurring every alternate cycle in that cylinder?  

     


  • Re: Rough running/High EGT in Cylinder 2

    by » 3 months ago


    Brad asked:

    ...  What caused the EGT in cylinder 2 to be higher when combustion was occurring every alternate cycle in that cylinder?  

     

    Well, once again just speculating...

    Since the fuel was not ignited within the cylinder, when the exhaust cycle occurs the un-burnt fuel vapor is going to be pushed into the exhaust pipe.

    Your EGT sensor is telling you that the exhaust pipe or at least the sensor itself is at 600°F or more.

    Gasoline vapor has an autoignition point of a little under 550°F so the un-burnt fuel will spontaneously ignite as it comes in contact with the EGT sensor.

    This places the EGT sensor in an open flame making it even hotter.

    Does that sound like a plausible explanation?


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: Rough running/High EGT in Cylinder 2

    by » 3 months ago


    Thanks Bill.

    Yes, auto-ignition of the un-burnt gasoline vapor triggered by the exhaust manifold temperature being higher than the auto-ignition temperature of gasoline of approximately 550 F would explain the EGT observations.

    The engine was not happy running on 3.5 cylinders, and even less so on 3 cylinders.  It's good to have a smooth running engine again.

    Thanks again for all your help and shared knowledge Bill.

     

     


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