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  • Re: High EGT's and low RPM

    by » 8 months ago


    Put the loaner ECU in, no change.  

    Frustrated......


  • Re: High EGT's and low RPM

    by » 8 months ago


    Let's get back to reality with what we know.

    There are at least 40 intermittent faults on the Lane "B" 3-4 ignition coil.

    And a strikingly similar number of Lane "B" MAT Faults.

    What do these have in common ???

    They both derive their power from the Center "B" Connector on the Fuse Box.

    And they both terminate on the Center "B" connector on the ECU.

    You already cycled the ECU connector when you swapped the boxes but it would be prudent to inspect the connector pins on the harness with 10x magnification for any irregularities.

    The same goes for the "B" connector on the Fuse box.

    - - -

    Notice!!!

    The ECU connectors are only rated for TWENTY(20) insertions!!!

    You used up 1 insertion swapping the ECUs.

    Keep in mind that only the original ECU has the correct Hobbs times in memory.

    If you intend to replace your original ECU, do it at the same time you inspect the connector and mark 2 connector cycles in the logbook.

    = = =

    What are you supposed to do after removing the ECU connector 20 times?  (Are you Sitting Down!!!)

    You are supposed to replace the ECU AND the Complete Engine Wiring Harness!!!  $$$$$  Outch!!!

    Ref. Heavy Maintenance Manual, Section 76-10-00, Pages 9 and 19. (Also see Pages 7 and 8)


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


    Thank you said by: Paul Depperschmidt, RotaxOwner Admin

  • Re: High EGT's and low RPM

    by » 8 months ago


    Thanks Bill,

    In one way it is a relief.  That ECU is expensive and it looks like that will not need to be replaced.  I did run the plane after the original ECU was reinstalled.  I will check for faults in the morning. 

    The connections for the ECU were checked prior to re-installation.  They all looked fine. At this point I am finished pulling those connectors.  I am aware of the 20 connection limitation and want to limit that activity.  

    I did pull the center (B) harness on the fuse box.  Nothing looked wrong. But I may go back to that.  As you say, it seems to be a funnel point of errors.

    With that said, the original issue of high EGT's has not come back at this point.  The engine is just limited in power.  No fault lights, no engine readings out of normal range.  And with almost everything on the 912is having redundancy and examples of that type engine running fine with most sensors failed, it just seems like chasing the electronic part of the engine is not the first priority at this point.  

    I have someone that is willing to help me check prop pitch on Monday.  It does not seem likely, but needs to be eliminated.  Then we may start to look again at the fuel system. None of the injectors have been checked or cleaned.  We might pull a couple just to take a look.  It might be interesting to pull the MAP and MAT sensors to take a look.  I have checked and secured the connectors, but have not looked at the sensors themselves.  

    It got up to 5000RPM for a moment today with a run up.  It can fly, so I might take it up in the morning.  It just does not have the power I am used to.  But maybe some flight will shake something loose.  


  • Re: High EGT's and low RPM

    by » 8 months ago


    UPDATE - While looking over the engine again for anything out of order I found that a small crack on the muffler had opened up again. There was not really any thought it could be part of the RPM problem. Then I removed to muffler to find that the central baffle had broken apart and pieces of it were rattling around inside. While playing with it I grabbed this picture of one of the parts covering the exhaust pipe. Think that could affect RPM's? :)

    😎

    25095_2_013cf5b3e6f7b4e181cee68b3652cc7f871f6fae5f.jpg (You do not have access to download this file.)

    Thank you said by: RotaxOwner Admin

  • Re: High EGT's and low RPM

    by » 8 months ago


    A blocked exhaust will cause back pressure in the cylinders.

    If you can't get the exhaust out, you can't get more fuel in.

    This could produce High EGTs and Lower RPMs and would affect All cylinders equally.

    I would move the muffler up to the top of the suspect list.


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


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