914 temps

[rhtrudder]

Just fitted a coolant sensor in the radiator hose between the collector and the radiator, went flying and was surprised that the temperature got up to 100 degrees, the sensor in the head only showed about 80 ,  did drop back to 90 as I came into land, was a cold day, I did wonder how accurate the original gauge was , oil temperature was down , rotax allows up to 120

[skippydiesel]

Rotax recommended temperature range are for the Rotax location of the sensor. By placing a sensor in a non Rotax location you are on your own ie what significant is there in your auxiliary sensors reading???

 

Liquids in an IC engine will experince diffrent temperatures in diffrent location's. What matters is, the temperatures are within the Rotax recommended range.

 

Coolant getting to 100C, on extended high power  Climb/TO seems to be quite acceptable to me.

 

The engine oil should also get to at least 100C, for an extended period (20min?) once in every days flying. If not getting there, you should consider blocking off part of the Oil Cooler.

I do this every winter (temp consistently below 25C).  I use aluminium foil, adhesive, air conditioning tape, to do the blocking.  Be cautious, only block off a small area at a time (eg two bars of the cooler). Go fly, check oil temperature. Once you have found the correct amount for your engine/climate, take a photo for future late autumn reference.😈

[rhtrudder]

Point taken, I think the later engines have the sensor in the coolant and not on the head, I have blocked off part of the oil cooler to get the oil temps up, I was surprised that there was as big a difference between the two readings, maybe the head temperatures are not as accurate 

[skippydiesel]

Speculation:

 

If this is an early 914 the sensors are reacting to Cylinder Head Temperature (CHT)

 

As you have alluded, Rotax later 914's had the senors registering Cylinder Head Coolant Temperatures.

 

I guess that Rotax felt that CHT was not especially meaningful for an engine with liquid cooled heads.

 

If you are concerned about your engines coolant temperature;

• Later Engine: I think finding a way to read the temperature at the same location as Rotax would be advisable. May need a stand alone gauge/sensor.
• Early engine:  This might be a question for the Rotax Owners Forum - Where you should locate the sensor for a meaningful reading & what temperature (at this location) would be acceptable??

https://www.rotax-owner.com/en/rotax-forum

 

😈

[rhtrudder]

Where I located it would be the hottest part of the circuit,I thought , I checked out the Rotax forums where there are well informed contributors and looks like the liquid pumps around that fast it wouldn’t make much difference where it was located , anyhow just another gauge to look at.

[skippydiesel]

3 hours ago, rhtrudder said:

Where I located it would be the hottest part of the circuit,I thought , I checked out the Rotax forums where there are well informed contributors and looks like the liquid pumps around that fast it wouldn’t make much difference where it was located , anyhow just another gauge to look at.

I think you will find that in all liquid cooled IC engines, the coolant will be at its hottest close to the combustion chambers and coolest where it leaves the heat exchanger/radiator.

The engine manufacturer (Rotax) will decide on the optimum point in the cooling system, for sampling the temperature as an indication of system operating condition.

My knowledge is limited to 912ULS - there are two coolant temperature sensors - in head 2 & 3

😈