Announcement

Collapse
No announcement yet.

Rotax 912/914 oil temp sensor placement / readings

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Rotax 912/914 oil temp sensor placement / readings

    Autogyro installs an oil sensor in the oil tank as the main sensor for the temp gauge, the uses the oil pump sensor for a warning light. Ive recently installed an AVMap Engibox which gives more specific readings over the old analog gauge (now I cant stop looking at it! ).

    My question is, does anyone know the typical temperature difference between oil entering the engine (oil pump) and oil exiting the engine (oil tank)? I may install a gauge on the sensor running to the light, but just thought Id ask first. Obviously if the tank temp is in the green, then Id think the other should be too.

  • #2
    It depends on the oil cooler location in the circuit. Usually, the cooler is between the tank and the pump so the oil temp at the pump should be cooler than the oil at the tank. I would almost have the warning light on the tank and the gauge at the pump sensor so you know the oil temp feeding the engine but either way works as long as the "green range" is set accordingly.

    Comment


    • #3
      The cooler is between the tank and the pump (standard configuration). I may hook up a second gauge just to find out the delta, but wanted to see if anyone already knew the typical drop in temp from the cooler. This would also be interesting for those that have the sensor at the oil pump to know what the temperature increase by the time it gets to the tank. If it's a sustantial increase then that would be worth knowing.

      Comment


      • #4
        not really worth it unless you are testing oil coolers or ducting. You need to care about the oil temp entering the engine that meets rotax specs.

        Comment


        • #5
          Not worth what? Not worth knowing? I disagree. The sensor is already installed on the hot side by AutoGyro already (on many newer AutoGyro gyros). If there turned out to be a significant difference between the cool side sensor and the hot side sensor, that would be meaningful.

          Comment


          • #6
            Originally posted by magknight View Post
            If there turned out to be a significant difference between the cool side sensor and the hot side sensor, that would be meaningful.
            I'm not here to argue with you. I was trying to share my extensive experience designing cooling systems on engines and save you a few dollars but go ahead and knock yourself out. I won't bother with you in the future but please tell us all what you find "meaningful" when you see a delta temp (duh). Also tell us all when that delta increases and decreases with ambient changes and altitude changes (duh again). Oh and not to be obvious but please let us all know the reason the delta changes with throttle/load changes. (duh duh duh).

            Hint - There isn't a "typical drop" and no one is going to be able to answer that one!

            Last edited by HighAltitude; 07-07-2018, 04:42 PM.

            Comment


            • #7
              The information is "Meaningful" because the aircraft manufacturer has moved the temperature sensor from the Oil pump to the Oil tank.
              They wanted to add an Oil Pressure switch to the system which needs to be in a pressurized zone and so moved the temperature sensor, which does not need to see pressure, to the oil tank.
              There is no mention by the manufacturer that the Oil Temperature limits are changed due to the relocation.
              This could be due to the fact that the temperature delta is so small that the differences can be ignored, or because the manufacturer forgot to publish a correction.
              We would like to think that the temperature is virtually the same or even a little higher giving a greater safety margin.
              Either way, Inquiring minds want to know! Everything is worth knowing!
              If it turns out that there IS a significant delta, the Oil temperature limits may need to be changed. Or, they may be fine as they are.
              Trust, but Verify!

              In your experience in designing cooling systems, What have you seen to be the Typical Temperature delta of fluids entering and exiting radiators?
              2? 20? 50? Lets put a number on it!

              Comment


              • #8
                Originally posted by Uncle Willie View Post
                The information is "Meaningful" because the aircraft manufacturer has moved the temperature sensor from the Oil pump to the Oil tank.
                They wanted to add an Oil Pressure switch to the system which needs to be in a pressurized zone and so moved the temperature sensor, which does not need to see pressure, to the oil tank.
                There is no mention by the manufacturer that the Oil Temperature limits are changed due to the relocation.
                This could be due to the fact that the temperature delta is so small that the differences can be ignored, or because the manufacturer forgot to publish a correction.
                We would like to think that the temperature is virtually the same or even a little higher giving a greater safety margin.
                Either way, Inquiring minds want to know! Everything is worth knowing!
                If it turns out that there IS a significant delta, the Oil temperature limits may need to be changed. Or, they may be fine as they are.
                Trust, but Verify!

                In your experience in designing cooling systems, What have you seen to be the Typical Temperature delta of fluids entering and exiting radiators?
                2? 20? 50? Lets put a number on it!
                Thanks, that is an important point that I didn't include (about the installation of the pressure sensor in place of the stock oil temp sensor. I've seen oil coolers on cars and motorcycles that decrease temperatures 20-40f from one side to the other, so I would be really suprised if it was only a 1-2f difference.

                Ultimately you hit on what I'm after, does the temp range need to change. I fully understand there are a lot of variables and no one answer, but even a range would be interesting.

                Comment


                • #9
                  Originally posted by magknight View Post
                  ... I've seen oil coolers on cars and motorcycles that decrease temperatures 20-40f from one side to the other, so I would be really surprised if it was only a 1-2f difference...
                  I have seen Oil Coolers that lower the Overall System Temperature by 20-40F.
                  It might be a leap to claim that there is a 20 temp drop across the cooler itself.

                  Ultimately you hit on what I'm after, does the temp range need to change.
                  It is to be expected that the Tank temperature is going to measure slightly higher than the Pump Temp.
                  So instead of getting excited at 130C, you might be OK up to 135C. (<<< Corrected!)
                  Without any temperature correction, you will end up treating your engine more kindly. Not a bad thing!
                  And this is probably why Autogyro makes no adjustments.
                  - - - - - - - - - - - - - - - - - - - - - - - - -

                  The flow rates are way more than one would assume.
                  The 912 Oil pump moves ~3 ml per revolution.
                  That means it pumps ~15 liters per minute at 5000 rpm!
                  The assumption might be that all 4 liters circulate through the oil tank and radiator about every 15 seconds but this does not take into account that the oil pressure regulator bypasses any excess oil back to the intake side of the oil pump.
                  A non-trivial portion of the oil circulates in a tight loop around the pump.

                  Still, it is not unreasonable to think that the total volume of oil makes the full circuit in well under 60 seconds.
                  Any given portion of the oil will only spend a very few seconds passing through the Oil Cooler.
                  There is not much time for the Oil to give up its heat.
                  It makes a lot of passes through the cooler to make up for the small amount of heat lost on each pass.
                  The overall effect is that the Oil is almost the same temperature everywhere.

                  We await your results.
                  Last edited by Uncle Willie; 07-08-2018, 10:49 AM.

                  Comment


                  • #10
                    Uncle Willie are you sure that the oil temp is 230c that would be 446f I thought oil started breaking done at about 270f.
                    Best Regards,
                    Eddie Sigman,Polvadera,nm
                    (575) 835-4921

                    Comment


                    • #11
                      Originally posted by eddie View Post
                      Uncle Willie are you sure that the oil temp is 230c that would be 446f I thought oil started breaking done at about 270f.
                      Good Catch!
                      Fat Fingers! Make that 130C.(266F)

                      Comment


                      • #12
                        Interesting subject. I have a 2012 Cavalon and very rarely do I see the oil temp get into the green. Maybe on a really hot day and on a long climb, my oil sensor is on the engine near the oil filter. The later Cavalons with the oil sensor on the oil tank are constantly in the mid to high green range.
                        i also have a 2015 Mto with the sensor on the oil tank and oil temps are always in the green.
                        Last edited by Rick E; 07-14-2018, 02:34 AM.

                        Comment


                        • #13
                          Yesterday I re-watched the excellent YouTube video by Lockwood on the 912 (two 1-hour videos of an intro course). One point made was that the reason Rotax recommends not going to higher RPM before the oil is 50c is that, below that temp, the viscosity of the oil may be high enough to have the oil filters spring-loaded bypass engage and allow unfiltered oil to circulate. Does Autogyro recommend a higher minimum oil temp, to account for this, since its reading the temp before the cooler?

                          /Ed
                          Last edited by EdL; 07-13-2018, 08:13 AM.

                          Comment

                          Working...
                          X