My MC and high oil temp?

[Roger Lee]

Cut from another forum, but a good question whether it is a CTSW, CTLS or this Gentleman's MC.

 

The Question:

 

Pioupiou Location: Muret, France

 

High Oil Temperature - Cowling design

Hi everyone.

 

We just received the first European registered MC in Muret - France LFBR.

 

We have these days high ground Temperature (35°C-95°F), and in our first flights, we encounterded some trouble with the Engine Oil Temperature (118°C-240°F) when flying in the airfield pattern.

We think that the engine cowling is not adequate with the air flow necessary for cooling the engine.

First, the exhaust pipe is just in front and at the same level of one of the holes under the aircraft.

These holes are probably not evacuating hot air properly. In high angle of attack - low speed configuration, the air pressure must throw the hot air comming from the engine back to the engine bay, as well as hot air comming from the exhaust pipe on the right side.

This, combined with low speed configuration, and hot outside air temperature condition, makes the rotax a bit too hot.

 

Have anyone experienced this problem, and what solutions have you found to solve it?

To be more precise, a CTLS flying by the same time had a normal oil temperature of 100°C-210°F.

Except that, the aircraft flyes very well, safely, and should be easy for training our future pilots.

 

Regards.

B. CHRISTIAENS, Aeroclub MERMOZ Vice-president

ACJM

 

 

The Answer:

 

On a 95F day 240F oil temp. on a climb out may be normal and if that's all you ever see then don't fret. The max temp for the engine is 266F and that's if you use Evans. If you are using a 50/50 coolant then 248F is max because Rotax is worried that there might be 1-2 hot spots that might vaporize and not get enough cooling. Your Evans has a boiling point of 370F where the 50/50 coolant is 270F. So Rotax thought 266F was a little too close to 270F for comfort. The problem with Evans is it raises temps across the board approx. 30F which puts you really up at max temps.

 

Now what can we do to help bring down that 240F

if you are so inclined

. Well for one thing prop pitch plays a big part here. If you have too course a pitch it will make the engine work way harder than it has too and temps climb quick. If the pitch is too flat the same may happen under certain conditions. So the best policy here is to make the pitch setup where Rotax recommends. You can also flatten your climb out on hot days and keep up a little more speed and work the engine less with less climb. During the hot months you can also move the clip on the carb needle down one notch and get a little more fuel which helps cool. I have done this and it dropped my summer time temps approx. 15F on oil and CHT's. It dropped the EGT temps approx. 80F. When the cooler months come back I'll simply move the clip on the carb needle back up one notch. I never get hot or even over 230F and I fly up to 105F and under full gross weight and high density altitude.

 

The biggest thing here is to have the right prop pitch, flatten the climb and if need be reduce throttle a little sooner. If you do the first two the last item may not even be needed. Other things that can cause this is a poor breathing air cleaner. For me I'd toss any paper element and put in a K&N. I never used to believe they made a difference , but I know for a fact that it plays a real part.

If you happen to talk to our friend in France you can let him know where to find his answer.