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.

[ofergd]

The ambient temps here at this season is around 70 deg F. i'm worried about the temperatures we expect in summer at around 110 deg F.
I know oil temps are relatively OK. The problem is with the water temps especially on the ground during taxiing.

OferGd

[rosslr]

HI Ofer

I to have a 912is sport - Yes, the oil temps are fine - very similar to what I get - in fact it is hard to get the oil temp up to the recommended 100"c during the cooler months. As for the coolant - I don't have any issues on the ground but on hot days it can get up to 110'c on climb - it settles in cruise - Mine is a SS7 so is different - I would be looking at airflow if you are already using the recommended coolant (which mostly have a boiling point of 130'c) sounds like you have a different airflow as others have suggested.

r

[ofergd]

Sounds great.
Can you send some pictures of your installation. Where the radiator is installed and how? and what is the air intake look like?
I need some ideas for improvement. I have the round bumpy cowl and it is hard to make the intake at the point where the rear and front cowls attach.

[rosslr]

Have a look here offer -

http://www.teamkitfox.com/Forums/showthread.php?t=5029&page=15

and there are many more to give you the idea of how the airflow happens in the SS7. I think it could also be worth chatting with John at the factory about his thoughts of how to best modify your KF4 for the 912is sport.

good luck

ross

[kmach]

Something to consider,
different propellers with their different blade designs push air through the cowl different. Some dont produce allot of airflow close by the prop hub, this affects temps on the ground.

[Guy Buchanan]

K-IV with 912uls. I don't think you should be having heating problems on a K-IV, there's plenty of radiator and oil cooler. Need pictures to see what you're doing. One thing I did that I don't know helped was to be very strict about shielding my oil and water lines from the exhaust, including shielding the oil filter. I know no one else does this, but it may have helped. (Indeed my problem is too low temps. 180F for oil and 140 - 160F for CHT's.) Remember the exhaust system is radiating heat at something between 800 and 1200F.

[Xengineguy]

Do you have a thermostat installed? If you do . It is sometimes almost impossible to get all
the air out of the cooling system w/o putting the system under a vacuum then
filling it. Most newer cars require this procedure.

[mr bill]

What kind of equipment do the auto people use to draw a vacuum? I have been wrestling with this issue since early November. For the moment I have no thermostat, but later in the spring when it warms up enough to work on it, I will resume work on installing a thermostat. Odd thing is, thermostat worked well when ambient air was above 45 F, but thermostat would not open when temp dropped below that.

[Xengineguy]

What kind of equipment do the auto people use to draw a vacuum? I have been wrestling with this issue since early November. For the moment I have no thermostat, but later in the spring when it warms up enough to work on it, I will resume work on installing a thermostat. Odd thing is, thermostat worked well when ambient air was above 45 F, but thermostat would not open when temp dropped below that.

Hi Mr Bill,
The vacuum system is available from snap on and many other vendors
maybe eBay also. It simply takes the place of the radiator cap
You hook an air hose to it and it creates a vacuum on the system.

The thermostat problem is likely lack of enough hot coolant to signal the thermostat to open. Do you have a small hose from the thermostat to the inlet
Side of the water pump? If you do you might need to drill one or two 1/8” holes
In the thermostat to bypass a little more coolant. More signal. Hope this helps

[mr bill]

I will try your suggestions after the weather warms up. My fingers don't work as well in the cold, as they used to. Thank you!

[ofergd]

A few answers and comments.
I am running a 912iS with computer controlled ignition and fuel injection. At full throttle it runs rich but below 97% power it turns to economical lean of peak, there for it runs hotter than the regular 912 ULS.
The big overheating problem is when on the ground while taxiing.
Anyway, thanks for the advise

Ofer Gd

[Gawilkie]

Not all oil coolers are equal in their ability to cool oil. My five kit came with an Earls cooler it could not handle the temps for the 912uls, it was located at the front of the cowling. I tried everything but it still ran too hot. I called Kitfox and John McBean told me the new oil cooler and the different mounting location would cure the temp problem. He was correct, now I have to tape parts of the oil cooler to get the oil up to temp. Cht and oil temps are somewhat related high oil temps contribute to overall engine temps. If you have the old style oil cooler replacing it with the new style will probably cure your problem.

[ofergd]

Also all cooling is related, I have problems with cooling the water. Oil tempetatures are high, but OK. Coolant temperatures are too high. I have an old type Rotax heat exchanger approximately 4" by 18" that I got with the kit. I just purchased the currant Rotax cooler with the same cross section area, and looking for an installation configuration to get sufficient cooling.
Maybe I should have baught the larger cooler from Jhon.

[Jaguar56]

Pulling plane out of annual I was at the runup area holding for inbound planes. Fairly stiff wind. I had turned the plane to watch inbound and the coolant temps started climbing fast. OAT about 85. Reached red and I shut it down.

Thinking I might have an issue, turned the plane in the wind and waited a few minutes. Started things up and seemed to hold a little over 200. Decided to launch and stay in the pattern. Once in the air the temps fell down to normal.

Lesson for me was to try and keep it in the wind as much as possible on the ground. Heat backs up fast when wind comes from the rear.

[efwd]

Hmmm. Good to Know. thanks
Eddie

[aviator79]

Lesson for me was to try and keep it in the wind as much as possible on the ground. Heat backs up fast when wind comes from the rear.

I teach my students to point into the wind in the runup area, and make the turn to check for traffic on final just before taking the runway. When air isn't blowing through it, the cowl makes a fine insulating blanket.