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I know this has been discussed and I have seen solutions for warming the circulating coolant and oil. So my Sirius TL3000 has widely separated and efficient water and oil coolers under the cowling.  The oil line has a factory mounted permacool thermostat, I am guessing it is around 170 F.  The oil is always below 180 F in flight even in the summer.  The engine head coolant temp lives at around 150 plus or minus. .  If you plug the cowling inlet duct to the oil cooler you do get a small rise in oil temp, which makes a little sense in that it effects the 10% or so of bypass oil flow.  Now I am thinking about placing aluminum tape over the coolant radiator to increase head temperature.   My main question is this.   In a ROTAX 912ULS, if I increase the coolant temperature, will I also get an increase in oil temperature?   Are the two cooling sytems somewhat indepedent of each other?  Or will one raise the temperature of the other?

  • Re: Engine temperatures

    by » 4 months ago


    If one goes up significantly then yes it will affect the other if they are seperated, but not a lot. If you are going to use the aluminum tape use it on both the radiator and cooler. If both are set back to back then temp changes may be a different from separated ones. Airflow through a cowl over these two items will make a difference too.


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


  • Re: Engine temperatures

    by » 4 months ago


    On my 912UL installation in my Eurostar, blanking off part of the coolant radiator raises the coolant temperature but also raises the oil temperature. This could be partly due to the reduction of air flow through the coolant radiator, into the cowling and out passing through the oil cooler on the way.


  • Re: Engine temperatures

    by » 4 months ago


    Yes one will raise the other, a hotter engine puts more heat into both systems. Your suggested tape method is a good one it is easily reversable if the outcome is not what you desire.

    However all fuel burning engines are basically heat engines so a hotter engine makes less power.

    180 F oil temp is fine as is 150 coolant temp, you may only need tape in winter but not in Summer.TL chose a 170 F thermostat for a reason.

    The Idea that you need to get to 212 F is a misunderstanding of the physics of heat vs vapour pressure of water. In simple terms at any temperature where water is a liquid some water vapor exists and this will dissapate into the atmosphere thus drying the oil. The higher the temperatre the higher this pressure and therefore the faster this happens. If you had a pot of water at room temperature it would eventualy evaporate and become dry. If you heat the liquid  from say 77F to 180F then the PP goes from 0.0313 to about 0.5 so the "drying" process is 0.5/0.0313 times (16 times) faster. Going to 212 F from 180 F is a litte faster but only twice as fast (1/0.5).

    As others have stated so long as you are not getting brown sludge cream under your oil cap then the moisture in the oil is being removed effectively and you do not have a problem.

    Rotax does state a minimm oil temp of 50 C and max of 120 C (122-248 F) so 180 F is fine.

     


  • Re: Engine temperatures

    by » 4 months ago


    Roger.  Thanks for your input!  Quick question.  My Sirius was Flight tested in Czexh republic in the fall of 2016, but by the time it was sent to the US and reassembled and flown it was April of 2017.  Should I be getting my 5 year rubber parts change in 2022 or 2021?  I only have about 150 hours on the plane, especially after 2020.  I read that you are experienced at this.  I have friends in Tucson.  Hard to find ROTAX people that are knowledgable.  Maybe I could fly out there from KJQF.

    Tommy


  • Re: Engine temperatures

    by » 4 months ago


    Thanks Kevin and Glen.  I think I will experiment especially with the winter here in NC. 

    Tommy

     


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