Low oil temperature on 915iS.

Inquiring Mind

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Oil temperature in-flight on my M-24 from day one was 90-91C. Never reached 100C. Obviously the thermostat opens up at too low temp. Does anybody has the same problem with originally installed thermostats?
Today I replaced originally installed thermostat with one from Improved Racing, model FSM-215,
Part NumberTypical Stabilization TempActivation TempFull Flow Temp
FSM-215 215ºF (102ºC) 212ºF (100ºC)233ºF (112ºC)
and finally I saw oil temp over 100C:


Before & after:
1634523716397.jpeg
 
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DavePA11

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Green arc is 90 to 110 C so it was on lower side. How much higher is it now?
 

Inquiring Mind

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Green arc is 90 to 110 C so it was on lower side. How much higher is it now?
I could get it as high as +110C stationary on the ground today running 3500RPM, OAT was +22C. Could not check in-flight as I finished the installation after sunset.
It suppose to stabilize at +102C in-flight according to manufacturer's data. That's exactly what I want - to boil water out of the oil.
Will see next Friday.
 
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DavePA11

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May I ask on another topic what is your rotor length? I’m thinking of buying another gyro for flying out around Rockies before I move back to NH or ME. Just have to find a place near an airport. You did a nice job on the installation of the thermostat too. Thanks!
 

Tyger

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You don't really need to hit the (sea-level) boiling point of water (100C) to have it evaporate out of your oil. 90C is quite sufficient.
The boiling point of water goes down by about 1 degree C for each thousand feel of altitude.
Besides that, just leave a pan of water on a warm (40C) radiator and see how long it takes to evaporate. :)
 
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Burrengyro

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8.8m.

Thanks. :)
Hi Inquiring Mind,
Very nice job on the oil thermostat. Did you have to change the Magni oil piping to suite the new FSM 215 unit? Did you have to purge the oil system? Looking forward to hearing how well the new thermostatic valve performs. I have no thermostatic valve in my ELA07S 914 turbo gyro and it takes quite a while to warm up and cool down. This FSM 215 looks very attractive especially if it performs better that the original valve supplied with the Magni M24.
Thanks, John H.
 

Burrengyro

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Hi Inquiring Mind,
What oil flow arrangement did you opt for: Standard flow, Reverse flow or Cross flow? Just wondering which option is best in the event of thermostatic valve failure?
Thanks, John H.
 

Inquiring Mind

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You don't really need to hit the (sea-level) boiling point of water (100C) to have it evaporate out of your oil. 90C is quite sufficient.
The boiling point of water goes down by about 1 degree C for each thousand feel of altitude.
I rarely fly over 2000' MSL, so 98C is still needed to boil the water in-flight.

Besides that, just leave a pan of water on a warm (40C) radiator and see how long it takes to evaporate. :)
Yes, from open pan water will evaporate in the open eventually, but in closed crankcase it will condence on internal wall (think - on valves, pistons, rings, crankshaft, push-rods, etc) and go back to the oil to rust everything inside. I prefer to boil the water from the oil before I reach pattern altitude.
 
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Inquiring Mind

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Hi Inquiring Mind,
Very nice job on the oil thermostat. Did you have to change the Magni oil piping to suite the new FSM 215 unit?
Yes, I cut originally installed fittings connected to thermostat and installed new fittings to old pipes.
1634603884736.png
Did you have to purge the oil system?
Yes, every time oil system is opened in suction side of it(except draining oil tank) it need to be purged. I do it by Rotax instruction I enclosed below, except I don't pressurize the oil tank and I don't rotate the prop by hand, instead I use Start button (with all sparkplugs removed, of course).

This FSM 215 looks very attractive especially if it performs better that the original valve supplied with the Magni M24.
Thanks, John H.
I will post results here after flying with FSM-215. Hopefully I'll fly next weekend.
 

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Inquiring Mind

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Hi Inquiring Mind,
What oil flow arrangement did you opt for: Standard flow, Reverse flow or Cross flow? Just wondering which option is best in the event of thermostatic valve failure?
Thanks, John H.
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:
1634604462330.png
 

Tyger

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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. It's not going to condense on the valves and pistons, etc – those items will be well over 100C whenever your engine is running. Almost all the water produced by combustion goes out as vapor in the exhaust. What little remains will be carried away by oil flow into the oil tank where, vented to the atmosphere at the neck of the oil tank, it will evaporate.
Of course the temperature of the oil in the tank is always going to be higher than at the pump/oil sensor, since the oil cooler is between the tank and the sensor in the oil circuit.
 

Inquiring Mind

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90C is quite sufficient.
Sometimes I didn't even get to 90C.
I promise you that water does not need to be at its boiling point to evaporate very quickly, especially at indicated temps over 90C.
Sometimes it is 82C:
Oil T 82C in flight.jpg
It's not going to condense on the valves and pistons, etc – those items will be well over 100C whenever your engine is running.
It will condense after landing, when metal parts start cooling down first.
I feel better when I see 102C during the entire flight, and because it does not cost me arm and leg, I see no reason to fly with cooler oil.
BTW, I use only fully synthetic Mobil "Racing 4T" 10W40 motorcycle oil and ethanol and lead free gas.
 
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Tyger

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What made you choose that motor oil, as opposed to the AeroShell that Rotax recommends?
 

Inquiring Mind

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What made you choose that motor oil, as opposed to the AeroShell that Rotax recommends?
Rotax recommends motorcycle oil, which is formulated for the bikes with wet clutch, Magni recommends motorcycle oil too. Mobil 1 Racing 4T is exactly the oil for such bikes. BTW, I would not use fully synthetic oil if I had no access to unleaded gas, I'd use Aeroshell-4, which is semi-synthetic.
 
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Inquiring Mind

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"What Oil should I run in my Rotax 4-stroke engine?The oil that you want to use depends, to some extent, on what fuel you are using. If you are running exclusively automotive fuel, you can use a synthetic oil and go 100 hours between oil and filter changes. If you are running 100LL some or all of the time, you will want to change the oil you run based upon the 100LL use. Synthetic oil does not do a good job of suspending the lead and getting it from the engine to the oil tank.
If you are running automotive fuel most of the time, and go on a cross country, 3 or 4 times a year, that is long enough that you need to top off with 100LL to get home, you needn’t worry about changing the oil you use just for that. If you are running 100LL 30% of the time or more, Service Instruction SI 912-016 stipulates that you drop your oil and filter change interval to 50 hours. It would also be wise to change to an oil that is at least partially petroleum based.
If you are running Avgas 50% of the time or more, the same service instruction recommends that you drop your oil change interval to 25 hours. At that point you may want to go to an entirely petroleum based oil just because of the cost factor.
The oils that we recommend the most for those three categories are Mobil 1 Racing 4T (fully synthetic), AeroShell Sport Plus 4 (semi-synthetic), and Pennzoil Motorcycle Oil (a petroleum based oil).
SI 912-016 lists the requirements for oil quality, and also has some specific recommendations for oil brands and products. In all cases, and in all conditions we recommend that you stick with a motorcycle oil. Motorcycle oils are formulated for use in engines that have an integral gearbox and wet clutch – and that’s exactly what you’ve got in your Rotax. The only exception to that is AeroShell Sport Plus 4.
Sport Plus 4 was developed in an effort by both Rotax and Shell to produce an oil whose formulation was stable and well suited for the Rotax 4-stroke aircraft engines. It is, by the way, the only AeroShell product that is suitable for these engines. Do not use any other AeroShell product in your Rotax. The others are all intended for traditional aircraft engine types and will not treat your Rotax well."
 
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Inquiring Mind

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From Magni's Flight Manual

209-00-24C FLIGHT MANUAL, Issue B
24 July 2019

TITLE: M24C PLUS FLIGHT MANUAL
CODE: 209-00-24C
PRODUCT: M24C PLUS

3.17.3 LUBRICANTS
Oil: motorcycle oil of a registered brand with gear additives
if using aircraft engine oil, then only blended one
Oil specification:
- Use only oil with API classification “SG” or higher
- Due to high stresses in the reduction gears, oils with gear additives such as high performance
motorcycle oils are required

- Because of the incorporated friction clutch, oils with friction modifier additives are unsuitable
as this could result in a slipping clutch during normal operation.
- Heavy duty 4-stroke motorcycle oils meet all the requirements. These oils are normally not mineral oils but semi or fully synthetic oils
 
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Inquiring Mind

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I promise you that water does not need to be at its boiling point to evaporate very quickly,
Products of gasoline combustion are mostly water vapor and CO2. Some of it goes to crankcase, and condense on oil if oil temperature is below water boiling temperature at the flight altitude.
If temp of the oil were over 100C - water vapors would not condense on the oil and would not become a part of lubrication stream. That is my opinion and I don't insist it is correct, but as I said, it is easy for me to replace the thermostat and forget about that problem, be it real or imaginary. :)
 
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Inquiring Mind

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Really nice panel. I'd like to copy that when I get my next gyro!
Thanks. Dave! I'll be happy to help by answering your questions when you start building the panel.
BTW, since the above pic was taken I've redesigned the DIGI layout, now it looks like that:
1634616071225.jpeg
 
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