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EGT probe location reminder

in 912 / 914 Technical Questions 13 years ago
This last year I have seen a number of home built's and factory aircraft come in the shop with the EGT probes mounted either way to close to the exhaust port or way too far out. Here is the page from the Rotax manual and the proper location for your EGT probe placement to get the proper EGT readings.
EGTprobelocation.pdf (You do not have access to download this file.)

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

  • Re: EGT probe location reminder

    by » 13 years ago

    Roger,

    A short while back when asking about needle re-setting one notch weaker, (?) ou recommended EGTs were preferable. Though the 80 hp engine has no provision for EGT, I have ordered two jubilee clip type clamp on 'K' thermocouples plus a neat twin needle gauge.

    I'll be fitting them in soon.

    When I drill the pipes at 100 mm from the flange I see on the diagram you put up that the apparent position for the hole is facing the engine. Also 100 mm around the long curve is somewhat less in the inside curve. For ease of access drilling in situ, is it very critical exactly which side as the front sector would be easier to drill ?

    p.s. Off the diagram the 100 mm is not even shown as on the pipe surface but stands off approx. one pipe diameter (30 mm) - so the Centre Line distance to where the probe tip actually locates is .... what ?
    PPS. I suppose what they mean is use a tape against the tube to measure round outside bend wall & drill at right angles to the tube - which means on the exhaust centre line the porbe will sit a fraction less than 4" ??

    Regards,

    mike hallam [GB]
      
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  • Re: EGT probe location reminder

    by » 13 years ago

    Hi Mike,

    If I understand you right yes you can drill the hole on the outward facing part of the exhaust pipe.

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

    Thank you said by: mike hallam
      
    Report

  • Re: EGT probe location reminder

    by » 13 years ago

    The two probes (Jubilee clip style) arrived today & tomorrow I'll remove prop & cowling on my Rans S6 to access & drill the left & right front exhaust pipes at 100 mm from flange.

    Apart from deburring the outside of a hole - just big enough to accept the probe - is there anything else ?
    e.g. chamfer the hole, or is a square edge a better seal ?

    mike hallam.
      
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  • Re: EGT probe location reminder

    by » 13 years ago

    Probes as described now fitted simple drilled holes sized so they slid in to shoulder, outer cut edge lightly deburred by hand with a fatter drill bit. Probe positions (on Rans S6) were chosen to avoid being in the way of other stuff, it meant both probes are on port side.

    In flight engine feels it runs fine as ever, but the new twin EGT gauge show a 60 C discrepancy at 5,000 rpm cruise yet to be investigated, highest is 760 C (1400F). WOT on take-off & climb to 1000 ft shows a modest 760 both sides, to me that indicates main jets are good and discrepancy is needle position.

    Balancing Carb's is next then if still uneven attention to needles after a re-check that main jets as found aren't bored. [I bought a new pair of BMW dealers main jets to be sure of original size for when I pin gauge their ID's.)

    mike hallam.
      
    Report

  • Re: EGT probe location reminder

    by » 13 years ago

    A second Rans S6-116 (80hp) flight today to re-check EGT's before doing any carb adjustments.

    On climb-out front exhausts EGTs at WOT (5200 engine rpm) was :- Left 760 & Rt.790 C; & ditto for Horizontal WOT at 5550rpm.
    At 5,000 rpm S&L (approx. GPS 99 mph)they dropped to L 710 & R 750 C
    whilst 4,800 dropped each another 60 C - Is that rather too low ?
    Or do all engines have lower EGT's as power reduced ?

    mike.
      
    Report
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