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I have a 2005 Remos G3 with a 912 ULS and a FlyDat display. When CHT reaches 248 ºF the CHT display begins blinking and the light goes from green to blinking red. If CHT reaches 266 ºF the FlyDat will display a service message the next time it is turned on.

The aircraft is placarded with CHT Warning/Alert of 300/320ºF. The most recent Remos G3 POH, 3/12/2007, documents the same numbers for CHT; 300/320 ºF.

The Rotax Operator's Manual, Ed. 2/Rev. 0 Apr. 1, 2010, p. 2-6, documents max CHT with waterless coolant as 275 ºF.

Rotax SB-912-043 UL R1, 28 Aug 06, para. 3.2.1 documents max CHT as 266º and max coolant as 248 ºF (my plane uses waterless coolant and does not have a coolant temp display).

And finally, the FlyDat Operator's Manual, Rev. A 03/04, p. 11 says 912 ULS CHT warning/alarm values should be 275/302 ºF.

Do one of these sources take precedence? I would like to believe the placard and POH, and have the FlyDat reprogrammed accordingly, but is that the right thing to do?

FYI, the engine runs great, but on a warm day in the Sacramento valley, even throttling back below 5000 rpm shortly after T/O, the CHT will likely touch 266 ºF before reaching 3000'.
  • Re: What is best source for max CHT?

    by » 9 years ago


    Hi Franklin,

    Get rid of the Evans waterless coolant and your temps will probably drop 20F-40F. Waterless coolant is not recommended any longer. Using it carries a temp increase penalty. 50/50 coolant absorbs and exchanges heat much better due to the water.
    Next check your coolant hoses and make sure each one is perfectly round and does not have a reduced radius due to a sharp bend. If you have such a hose a stainless steel spring can be inserted to the bend point to keep the hose fully open.

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


  • Re: What is best source for max CHT?

    by » 9 years ago


    Roger,

    Makes sense from what I've read; greater thermal capacity with 50/50 vs. waterless. Will swap out Evans for Dex-Cool/water. If I get 20-40 ºF lower CHT, I will be ok with current FlyDat settings/warnings.

    Thanks, Frank

  • Re: What is best source for max CHT?

    by » 9 years ago


    Frank,
    If you change to 50/50 you need to add a water temp gauge (goes in the coolant hose). The limit for the coolant temperature is 120C. If you have the .9 bar cap you also need to change it to the 1.2 bar cap. See SB912-043 - http://www.flyrotax.com/portaldata/5/dokus/d02398.pdf

    Thank you said by: Jack Martin

  • Re: What is best source for max CHT?

    by » 9 years ago


    Conrad,

    Thanks for this input. I do have the 1.2 bar radiator cap. I will check with Remos regarding the addition of a temp sensor and gauge for the coolant.

    Looking at SB-912-043 R2 para. 3.2.1 the footnote implies that calibration of the CHT gauge may suffice in place of a coolant temp gauge, and the Rotax Installation Manual, Feb. 2015, Cooling System para. 2.1.1 describes the procedure for finding the CHT that matches the max coolant temp; 120 ºC/ 248 ºF. (Remos may have done this.)

    Frank

  • Re: What is best source for max CHT?

    by » 9 years ago


    My factory aircraft never came with a coolant temp sensor, only CHT.
    I do have 4 X EGT though....

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