Low oil temperature on 915iS.

Burrengyro

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I did not choose any options, I just replaced original thermostat without changing anything. I had no idea about those options. Here is the pic of the flow from manufacturer:
View attachment 1153468
Hi Inquiring Mind,
Many thanks for posting the images. Looking forward to your test flight results for temperature warm up time and what the stable temperature. Please measure the time it takes to cool down as well so we can be sure the turbo is cooled enough before shutdown to prevent coking of the oil in the turbo sump.
Many thanks, John H.
 

Inquiring Mind

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,
Many thanks for posting the images.
My pleasure, John.

Please measure the time it takes to cool down as well so we can be sure the turbo is cooled enough before shutdown to prevent coking of the oil in the turbo sump.
I will.
BTW, I had my turbo coked once, but I don't think 10C higher oil temp (102C vs 91C) would make any difference in terms of coking.
 

Inquiring Mind

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I promise you that water does not need to be at its boiling point to evaporate very quickly, especially at indicated temps over 90C.
Here is what happened last Sat: before first flight with the new oil thermostat I decided to run oil temp up to the allowed max of 120C (or as high as it would go below 120C) on the ground. Week before I run it up to 110C only and now I wanted to see what happens when 100% of the oil flows through the radiator. According to MFG that should happen at 112C. I started the engine and then oil temp reached 112C or 113C all the sudden oil pressure dropped to 0.8-1.0 bar and oil temp dropped to 99C. It took at most 5 seconds for pressure and temp to drop from 3.5bar to 1 bar and from 113C to 99C. I shut the engine down right away.
Oil tank vent tube was filled with the whitish-yellowish foam.

Care to guess what happens? If not - I'll post the answer.
 
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Tyger

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I don't know what's going on with your system, but I can tell you I rarely get as high as 90C (usually high 80s) and NEVER to 100C, even in hot weather, and I have yet to have the sort of problems you are describing, with 450 hours on my engine.
My oil pressure is usually up around 5bar right after a cold start, but once it hits 50C it gets down to about 4bar and stays there. I have never seen an oil pressure even close to as low as you are describing.
May I suggest you bring this up on the Rotax-Owner.com forum? Lots of sage advice is available there. :cool:
 
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Vance

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Care guess what happens? If not - I'll post the answer.
I have not had a problem like that with a Rotax 9 series engine.

When I get the foam in the oil of my Lycoming IO-320 I suspect it is because of water contamination in my oil.

When the water in the oil boils it makes white/yellowish foamy goo.

It usually happens when I allow the oil to get over around 210 degrees F.

Sometimes the oil cooler gets plugged up from the goo and I have to clean it out.

It has a lot to do with the duty cycle; short flights build up the water, longer flights tend to get rid of the water.
 

Inquiring Mind

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After 100 hours of flying with oil temp never exceeded 91C all the condensed water accumulated at the bottom of the oil radiator (the lowest point in oil system, right on the level of the taiboom).
Again on the ground I run oil temp to 112C, until new oil thermostat pushed 100% of the 112C oil through the oil radiator making water accumulated in it for 2 years of flying with 91C oil boiling. That caused rapid decrease of the oil pressure & temp and oil foaming.

After that I returned the gyro to hangar drained all the oil, replaced it with new oil, purged the system and run the engine to 112C again. As soon as the temp reached 112C it started slowly dropping and stabilized at 102C, exactly as MFG promised - ideal temperature, IMHO. Too bad Magni use oil thermostat with such a low activation temp. :(
 
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Inquiring Mind

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When I get the foam in the oil of my Lycoming IO-320 I suspect it is because of water contamination in my oil.

Exactly. And that water contamination in my case was caused by low oil temp in-flight.
It usually happens when I allow the oil to get over around 210 degrees F.

Water boils at ~212F at sea level, oil does not. So if you oil is boiling and foaming at 210F - you have water in the oil. Exactly my point.
 
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Inquiring Mind

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May I suggest you bring this up on the Rotax-Owner.com forum? Lots of sage advice is available there. :cool:
It is not about Rotax engine, it is about Magni oil thermostat and position of the oil radiator below oil tank.
Pephaps if oil radiator on M-24 were above the oil tank, as on M-16, the water would accumulate not in oil radiator, but in the oil tank, from where you drain it every oil change and not even notice.
 

Tyger

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Yes, I have an M-16, not an M-24. Mine does not even have a separate oil radiator.
If you really think it's a design and/or equipment flaw on the M-24 you should probably mention it to Greg Gremminger. I imagine you've already made Steve Bacon aware of it.
 
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Tyger

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It is not about Rotax engine, it is about Magni oil thermostat and position of the oil radiator below oil tank.
Pephaps if oil radiator on M-24 were above the oil tank, as on M-16, the water would accumulate not in oil radiator, but in the oil tank, from where you drain it every oil change and not even notice.
I think if there were a lot of (or any) water in my oil tank I certainly would notice it when I drain it. I have never seen any. The tank IS the lowest point of my oil system. It seems to me that oil should be drained from whatever is the lowest point during any oil change.
I believe that any water in my system evaporates once it gets to my oil tank, where it's exposed to the atmosphere at temperatures of 90C plus (the oil cooler being between the tank and the temperature sensor).
 
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Inquiring Mind

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Yes, I have an M-16, not an M-24. Mine does not even have a separate oil radiator.
M-16 with 912iS comes with the oil radiator and oil thermostat. Look at the oil temp in-flight, it is 108C, good:
1635311102211.jpeg
If you really think it's a design or equipment flaw on the M-24 you should...
I think their choice of thermostat temperature was wrong for my gyro. Not a biggie, I replaced the thermostat. I don't see any better place to put oil radiator on M-24, not much to choose from, but the low position of the radiator is not a problem if oil temp is above water boiling point.
 
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Inquiring Mind

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Yes, I have an M-16, not an M-24. Mine does not even have a separate oil radiator.
Instead of separate radiator your M-16 has a heat exchanger, which cool the oil to the coolant temp.
AFAIK Steve Bacon now is in the process of getting rid of that exchanger and installing the thermostat with 212F full flow temp and separate oil radiator.
 
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Burrengyro

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It is not about Rotax engine, it is about Magni oil thermostat and position of the oil radiator below oil tank.
Pephaps if oil radiator on M-24 were above the oil tank, as on M-16, the water would accumulate not in oil radiator, but in the oil tank, from where you drain it every oil change and not even notice.
Hi Inquiring Mind,
Many thanks for posting this information. My ELA07S has it's oil radiator positioned lower than the oil reservoir. I change the oil every 50 hours. I don't always get more than 95 degrees C oil temperature even with covering half the oil radiator in our Irish winter weather. This could mean some water is accumulating in the oil rad???. Thinking of covering 100% of the oil rad until oil temp reaches 100 degrees C for about 5 minutes to boil off any moisture out of the oil rad. In my ELA07S when oil is changed, the oil in the oil rad is not drained because of the oil rad position versus the oil reservoir position. When you did your oil system purge, did you remove the rocker covers and force the air out of the valve lifters or spin the engine using the starter with the spark plugs removed to circulate the oil and remove residual air in the system?

Looking forward to hearing about how the new thermostat is working for you and thanks for sharing your experience.
John H.
 

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What Is The Optimum Engine Oil Temperature?


For a dual-purpose car, engine oil needs to be at least 220 degrees F to burn off all the deposits and accumulated water vapor. For every pound of fuel burned in an engine, the combustion process also generates a pound of water! If engine sump temperatures rarely exceed 212 degrees (water's boiling point), the water will mix with sulfur (another combustion by-product) and create acids that can eventually damage bearings.

As for ultimate power potential, the general consensus among most racers is that hot oil and cool water make more power in most engines. Cold engine oil causes excessive frictional drag on the bearings and cylinder walls. A quality conventional motor oil will tolerate oil sump temperatures of up to 250 degrees, but starts breaking down over 275 degrees. The traditional approach is to try to hold oil temperatures between 230 and 260 degrees. Even on a short-duration, drag-only combo where oil is frequently changed, I would not want to routinely see under-200-degree oil temps.

A full-synthetic oil will withstand sump temperatures in excess of 300 degrees, and for hard-core professional racing, some oval-track race teams are experimenting with ultra-thin, specially formulated, race-only synthetics operating at 350 degrees or even higher.
 
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Vance

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In my opinion it is best to consult the engine manufacture for the optimum oil temperature range.

It has a lot to do with where the oil temperature sender is located.

Some engines may have fifty degrees higher oil temperatures elsewhere in the engine.
 

Inquiring Mind

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In my opinion it is best to consult the engine manufacture for the optimum oil temperature range.
No need to contact the MFG, as Rotax published the numbers for the 915 in its Manual:

Oil temperature:
Engine start -20 °C
Take-off 50 °C
Normal operation 50 °C - 130 °C
ATTENTION
Operating the engine below (90 to 110 °C / 194 to 230 °F) may
lead to formation of condensation water in the lubrication system.

To evaporate possibly accumulated condensation water,
at least once a day 100 °C (212 °F) oil temperature must be
reached.


From Magni Flight Manual:
OIL [°C]
min 50
normal 90 - 110
max 130
 
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