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912ULS EGT Differences

in 912 / 914 Technical Questions 13 years ago

  • Re: 912ULS EGT Differences

    by » 13 years ago

    The exhaust should be pulled periodically and copper anti seize put on the fittings at the muffler knuckle and the exhaust port. This keeps them from chafing and rubbing holes in them it also keeps them from getting frozen in place at the exhaust port from humidity and other moisture. Springs on the exhaust should be examined too every 100 hours to make sure they are not wearing through on the hooks where they will break.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: 912ULS EGT Differences

    by » 6 years ago

    I have a situation with a 300+ F EGT difference. This is a pusher, with EGT probes in the 1 & 3 pipes (i.e. nearest the prop), but after cyls 2 & 4 in the airstream - for what that's worth. All other temps look great.

    After 10 mins cruise around 5150 RPMs (25.3 mp), values are:

    Oil Temp: 205 F
    Coolant Temps: 182 F -and- 181 F
    EGTs: 1113 F -and- 1387 F

    So everything looks good except one EGT reads very low and is 300+ F off the other.

    Thoughts?
      
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  • Re: 912ULS EGT Differences

    by » 6 years ago

    1& 3 are on the same side. 3 would be up front and 1 in the rear.
    1 & 3 are left side and 2 & 4 are on the right. It would have been better to put them on either 1 & 2 rear or 3 &4 front. This may be part of your temp difference. They should both be 100 mm (3.9") from the exhaust flange. If they are not equal this would be another cause. Spark plug gaps that are not equal or too wide could affect this. The gap should be between .023 - .027.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Andrew Dunning
      
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  • Re: 912ULS EGT Differences

    by » 6 years ago

    Thanks for the reply Roger. Sorry, on the 1 & 3, my bad; thinking of wrong engine there. So, correction, probes are in 1 & 2, which is rear cyls on this pusher. probes are in correct location, and same location as several other models of this plane where EGT's are about as close as you can get (within 5-10 F) of each other. So I wouldn't think placement is the issue. I attached some photos. Just did 100hr on it and replaced all plugs with new, carefully gaped. All have heat transfer paste on them.

    Did have a grounding wire problem after annual and some flight time, which caused severe RPM drop on mag check. That has been corrected. Flight this morning had the EGT issue.

    Note, I also replaced the entire exhaust system on this plane at this last condition inspection as well due to the prior had cracks. New system installed with anti-seize paste.

    This seems to be an issue after the 100hr/annual condition inspection and a few hours flight time.
    2019-01-2316.13.46.jpg (You do not have access to download this file.)
    2019-01-2316.13.33.jpg (You do not have access to download this file.)
      
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  • Re: 912ULS EGT Differences

    by » 6 years ago

    It could just be a probe going bad. Depending on which probe you have they are about $35 - $40. You could swap probe wires and see if the problem changes sides or stays on the same side. If it swaps sides I would replace the probe before I worried about everything else.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: John Melchert
      
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