It's hot!!

[KevinC]

My oil temps, that is.

I've pm'd Scuba on the outcome of his previous post and consulted with Stede and have a first step in mind, and I wanted to ask the group if anyone else has solved this problem.

I have a Rotax 912 ULS. My oil cooler was the standard stock cooler and I have the oil thermostat many have used. My fittings are the right angle brass 'hardware -store' type included with the thermostat.

The opening in my cowling is ~1/2 inch smaller than the finned area of the oil cooler (going to remedy that tonight). There is no baffling around the cooler.

I run cool in the winter (170) and now that it is really hot I'm having a hard time keeping it below 230 - like 4800rpm max. With a recent trip to Idaho I really wanted all that power!

Anyone else have this problem and if so how solved?

thanks!

k

[scubarider2]

I still have some issues from time to time but it is mainly only when really hot out and I try and climb climb climb. When I level out and run about 5200rpms the temp drops back down to acceptable.
The oil cooler I have is standard that came as the package buy from JA. It is open fully to the air through the cowling. See how I attached in picture.
Dennis

[foxred]

first thing I would try is put baffling on your cooler force the air to go through it not around. Same princeable as your radiator. More air more cool. Just my two cents hope all works out.Same thing here in Kansas hotter than hell.Happy flying.

[alan]

Kevin,

Has the engine ever run cool in the summer with the thermostat? There is a small amount of bypass around the cooler with the thermostat installed. Making the air intake the same size as the thermostat and adding baffling to force all the intake air through the cooler should help. My Highlander with no thermostat and no baffling has never run hot but the hole is slightly larger than the cooler.

Alan

[KevinC]

No, it has never run cool in the summer time. I usually just fly early and late and really low & slow - so although I've known it was an issue I was able to manage it that way. Now it is really hot here and I'm climbing for long periods so more of an issue. It might be worse than it has been, but I've always had trouble with temps near yellow when hot and high power.

Tonight I'm going to finish baffling and cutting out the inlet hole - we'll see!

k

[KevinC]

Update:

I removed material to expose all fins like this

iphone07_12 065a.jpg

and then added baffling material to make a seal with the cowling

iphone07_12 066a.jpg

the results:

90+ degrees oat
climb full power from 680 - 3500 and it was up to 225 and still climbing.
pulled back the power to 4500 and it dropped to 220, then back to 5000 and level = 220-221 steady.

So - it is definitely an improvement, but I sure would like to be able to use full power and no more than 220 on a hot day. Is that possible? Anyone else have similar experiences and/or suggestions?

thanks!

k

[danerazz]

Can't tell from the picture, but is your cowl exit adequate and what is behind the cooler? All the air in is useless if it can't get out. Generally the exit has to be a lot bigger than the inlet, and you may need a "lip" to help some negative pressure. Also, you might just need a cooler with a greater cooling capacity.

[Karl]

Hello,
We are using the ThermoStasis oil thermostat...no temp issues this summer in South Carolina.
Could you bypass or remove your thermostat unit with short hoses and clamps and such to see if it is the culprit?
Hope you find the solution.
Regards
Karl

http://www.vansairforce.com/community/s ... hp?t=54398

[Trilander Ted]

Reguarding oil temps, I'v always been told that oil starts to really deteriorate after 250*F, and thats why synthetics are blended in modren lubrecants. That said, my summer temps approch 230*F in 100*F OAT and I don't worry about it. Lately it's been afternoon temps above 116*F to 119*F and haven't flown for a month.( There's noplace I want to go when it's that hot) My engine has 975 hrs on it now, and in years past Iv'e recorded short borsts of 250*F in our Arizona sunshine. Rodger Lee ( a Tuscon Rotax repairman ) says that's way to hot, but the Rotax keeps chuggin' along just fine, so far. When I built my Highlander, I reshaped the lower cowl, I made the chin one inch lower to enable more air pressure to escape at the firewall aera and give more ram air to both raidators in front. All that extra fiberglass work hasn't seemed to help all that much in our summer conditions (So. Califorina, Arizona, & Nevada) desert. I too have an oil thermostat, and install it after long winter warmups. I have changed to Mobil One 4 stroke M/C oil, about one & a half years ago,(seems like I have good results so far). I may be "nuts" for letting oil temps run up that high, and wonder what others think???? Knowone seems to notice the one inch "drop" in the lower cowl that I spent so much time on to accomadate the Arizona Sonoran Desert. Trilander Ted

[User GDS]

Here's a link to a Rotax Service Instruction on suitable operating fluids:

http://www.rotax-aircraft-engines.com/p ... d04899.pdf

It says to "Keep the motor oil temperature below 120C (250F) over most of the operating period." In other words, do not go above 250 for more than 50% of the time the engine is running.

I've got an RV12 with a Rotax 912 and during summer climb-outs it always goes up to about 238 degrees and stays there until I level off. I just keep climbing and monitor the situation, I don't think it is a problem for the engine.

[Trilander Ted]

Thanks Gary, I feel vindicated now after reading the Rotax publication. There oil rating system tells the story, I.E. synthitcs do the best job for high oil temps, and are O/K to a point. It was interesting to note that the EVANS coolant was rated max cold temps, but didn't suggest the upper limit of the nine series engines, only that EVANS+ must be full and it will not boil. As you know, I can still get non ethanol motor fuel that helps with engine service with the Mobil One products. ( notice: they refer to certan "political reasons" for the differant types of fuel, boy, they got that right!!) I know 10% Egas is O/K, I will resist it when I can, it might help cool temps a whisker at the cost of a little power. Indiana & Illinois are in enough trouble with drought that the corn crop is about "history" now and bacon runs best on corn and cars like gasoline, save the corn for taco shells. After all, maybe I'm still going "nutz" Trilander Ted

[SheepdogRD]

The Rotax is both air-cooled and liquid-cooled, so some air-cooling system tips apply. We won't be flying behind a Jabiru, but I found this PDF of cooling tips from the Jabiru manual to be both interesting and helpful.

[KevinC]

Ok - time for a follow up.

After talking with several other Highlander folks I removed the 'lip' at the outlet of the cowl (approx 1" that runs parallel to the floorboard) in addition to what I removed around the oil cooler and the baffling. Tonight I flew the airplane at ~90 deg ambient and got the following:

5000 rpm; 223 deg steady
5250 rpm; 229 deg steady

I think I'll declare victory.

k

[scubarider2]

Still sounds too hot to me.

[taildrgfun]

Ronnie Smith told me that 260-270 won't hurt a thing with Mobil 1 MX4T full synthetic oil. I've never seen mine that high but it is nice to know.