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Coolant Temp Sensors 912ULS2

in 912 / 914 Technical Questions 8 years ago
Hello. I have a cowled, tractor installation (Zodiac 601 HDS) for a new 912ULS2. The coolant temp sensors are on cylinders 2 and 3, and the cylinder with the highest temp should be measured. Is there an accepted highest temp cylinder for this type of application or does it have to be determined by testing during flight? Thanks.
Regards,
Damien Graham
N48TK

  • Re: Coolant Temp Sensors 912ULS2

    by » 8 years ago

    Hi Damien,

    On the 912ULS the CHT isn't actually in the coolant. It is only reading the metal temp at that location. Typically the two CHT's run approximately 10F from each other. You could use either, but most use the #3 CHT as it could be the warmer one, but not necessarily. It just depends on the engine cowling air flow set up and the coolant radiator set up. The coolant in this engine only cools the heads. Your max CHT temp using a 50/50 coolant is 248F which usually will lag behind oil temps. Don't use Evans waterless coolant. Most people's oil temps get too high before the CHT's ever do.

    On my Flight Design the CHT's tend to be about 10F-20F below my oil temp, but this may be different for different aircraft and their engine setups, cowl air flow and oil cooler and radiator setup. OAT's play a part here too.

    Did my fumbling around help any?

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

      
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  • Re: Coolant Temp Sensors 912ULS2

    by » 8 years ago

    Thanks for the reply Roger.
    As a review, we are hooked up to #3 now, and we are monitoring a temperature gauge which we have marked at 248F Max. So if I have read correctly we should be OK, with the caveat that in my application maybe the #2 cylinder might run hotter, the difference being about 10 degrees.
    So if I keep this "coolant" gauge reading below 248F, then I would not be in danger of going past the max CHT of 275F.
    Thanks again.
    Regards,
    Damien
      
    Report

  • Re: Coolant Temp Sensors 912ULS2

    by » 8 years ago

    The engine might handle 275F, but the coolant can't. 50/50 boils at 270F-275F and if that happens you will form vapor spots in the heads and will overheat and cause damage because there will be vaporss there and no coolant.

    Just consider 248F as a never exceed number no matter what and if it ever did get up there it's time to get back on the ground and find out what's wrong. I live in the SW US where day time summer temps are 100F+. I may see 230F and some people see up to 240F on climb, but only run 215F-220F in cruise and CHT's are lower. If I ever saw high temps well beyond what is normal I would want to know what changed and why.

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

      
    Report

  • Re: Coolant Temp Sensors 912ULS2

    by » 7 years ago

    Hi Roger,

    I am running 50/50 Silica Free coolant in my 912ULS with CHTL and CHTR into a Dynon Skyview.

    I read in the 912 Installation Manual that when using conventional cooling, "Permanent monitoring of coolant temperature and cylinder head temperature is necessary." Do I have to add a coolant sensor?

    This is not a suffix -01 engine.

    Best,
    Keith
      
    Report

  • Re: Coolant Temp Sensors 912ULS2

    by » 7 years ago

    Most don't. Most people pick one or the other. The owners with the engines pre coolant probe mounting on top of the cylinder usually only monitor the CHT mounted under the cylinder. I don't think I have a single client that does both.

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

      
    Report
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