Rotax 912iS overheating

[ofergd]

As previously posted here, we installed a Rotax 912iS on a KF-IV.
Now, during our phase 1 test flights we are having overheating problems, especially on the ground.
We installed the coolant radiator under the belly of the plane, with and without the scoop. With no significant differance.
we get 220°F coolant and 200°F oil temperatures.
What is your experience with overheating of 912 engines.
Does anyone baffle a 912 engine?

[Esser]

You can make a fiber glass plenum to direct air over the fins. Are you running an oil cooler? What size is your rad?

[Dave S]

Ofergd,

Which coolant are you using? Rotax approves either evans waterless or ethylene glycol mix.

Although we did not have an overheating issue - the glycol mix (Dexcool mixed 60%) resulted in 20 degrees F lower running temp than the Evans under similar conditions. This also resulted in a lower oil temp.

Have you verified the accuracy of your temp indicator? They have been known to lie a little on occasion. Reading the instrument while boiling the probe in plain water should show 212 F or a little lower if you live at a higher elevation.

[kmach]

200 F is okay for oil temp. you want to hit 212 F oil temp at some point in your flight.

[ofergd]

I'm using a Rotax approved coolant, but I don't remember which type. I have the Rotax 912iS engine which has an ECU and I get all reading by computer communication to my display, so I have to believe it is pretty accurate.
I was thinking of making a plenum, but it seems a lot of work. Did anyone make one for the 912? If so, pictures please. . .
The engine is mostly running LoP therefore it is running hotter.

[jiott]

What is your ambient temp during the test flight? In a fairly warm ambient, the 200F oil temp is not a problem at all.

Don't use Evans waterless coolant. It has fallen out of favor with Rotax, and I believe it is no longer on the approved list.