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"Boiling" Mad

R

RLH

I'm New Here
O.K. guys, I have tried everything I can think of but I just can't seem to get my oil temperature to stay in the green when the ambient air temperature is 86 degrees or above! And if I try to climb in such temperatures I get right to the top of the yellow really quickly!:eek:

I have spent my life savings and four years of my life building an airplane that I hope to retire to Florida with. Now it seems like the thing will only fly in cold weather!:mad::confused:

There has got to be a solution to this problem!
 
oil temp

Baffle leak, too small cooler, bad varitherm valve, or bad temp sensor. What else could it be?
 
RLH said:
O.K. guys, I have tried everything........
There has got to be a solution to this problem!
Click to expand...

Many of us have seen RV-12 oil temperatures higher than we would like to see when the ambient temperature is high. At an OAT of 85-90 degF in humid conditions, I can easily see temperatures greater than 230 degF (start of the yellow arc) during a climb at 85 knots at full power. Forces me to level out, reduce power, let the speed build and let the oil cool.

A couple of items that have helped are as follows. Ensure your prop pitch is set to attain a static rpm of 4980-5000 on the ground at wide open throttle (WOT). This should equate to 5500-5650 rpm at WOT after accelerating to a maximum speed when flying.

Second, ensure the seal between the cowl and the water radiator is tight ALL the way around. This will ensure all of the airflow available is being forced through the oil radiator and there is no leak by.

Third, after the plane has been sitting overnight, letting all of the temperatures stabilize to ambient, compare the CHT, EGT and oil temperature indications. They should be close to one another. You could also remove the oil temperature sender and put the tip in a boiling water bath (212 degF).

Van's will tell you that you can go to red-line without a detrimental effect. Van's has NOT taken any action to address this issue. The climate in Oregon is a bit different than some of our climates.

I tend to err on the conservative side based on a number of conversations with those that know the Rotax 912 intimately. I will let the oil temperature enter the yellow arc and then take measures to let the oil cool.

Some see the high oil temperatures and some, for some reason, do not. This population includes those in Florida and Texas. No one, to my knowledge has been able to explain this difference. I have one theory, but, have not taken the time to see if there is a correlation. The muffler can be moved forward and aft a bit before the bolts are tightened. This changes the distance between the 1200 degF muffler and the fins on the aft side of the oil cooler. I cannot put my small finger between the two components. It is close!!

Let us ALL know if find or run across a solution. If you do a forum search on "high oil temperature", you will find a number of threads.
 
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Another note - -

Some did not cut the opening on the lower cowl as directed to. Another maybe ! We have had hot days in Iowa this year. With WOT for long periods, I can get mine up to the yellow also. Takes a while, so not sure what you are actually seeing. As Marty said, if you let the speed build some, then you can manage it. Climbing at 85 kts helps, rather than 75 kts.

John Bender
402.8 hours
 
MartySantic said:
A couple of items that have helped are as follows. Ensure your prop pitch is set to attain a static rpm of 4980-5000 on the ground at wide open throttle (WOT). This should equate to 5500-5650 rpm at WOT after accelerating to a maximum speed when flying.

Second, ensure the seal between the cowl and the water radiator is tight ALL the way around. This will ensure all of the airflow available is being forced through the oil radiator and there is no leak by.

Third, after the plane has been sitting overnight, letting all of the temperatures stabilize to ambient, compare the CHT, EGT and oil temperature indications. They should be close to one another. You could also remove the oil temperature sender and put the tip in a boiling water bath (212 degF).
Click to expand...

I agree with Marty, these are all good things to check.

MartySantic said:
Van's will tell you that you can go to red-line without a detrimental effect. Van's has NOT taken any action to address this issue. The climate in Oregon is a bit different than some of our climates.

I tend to err on the conservative side based on a number of conversations with those that know the Rotax 912 intimately. I will let the oil temperature enter the yellow arc and then take measures to let the oil cool.
Click to expand...

With this I disagree.
I believe everyone at Van's tells builders the exact same thing that Rotax says in there own documentation. That intermittent short duration (5-10 minutes)excursions into the yellow range during climbs in hot weather is acceptable. If the oil temp doesn't go back into the green range after a cruising level for a while, then you probably have some type of a problem.

BTW, If you can't believe what the people who design and build the engine tell you, then who can any of us believe? Why should we be listening to people at the U.S. service centers instead? They know even more about the engines than the manufacturer does?. Is the air different here in the U.S. than it is in Austria? Can you really fault anyone at Van's for designing systems based on engineering information that the engine manufacturer provides? (sorry for the rant)

Please keep in mind that the prototype RV-12 now has more than 600 hrs., with a lot of that flight tame occurring while it was flown all over the western U.S. in the heat of summer. During flight testing it was specifically sent to Death Valley CA to do some hot weather testing. It has made a couple of trips to the Copper State Fly-in, in Phx Arizona. I have attended many years that temps were still reaching into the low 100's. It is not a fair assumption to assume that Van's is located in some type of weather vacuum that never sees temps higher than 70 deg F. Not true, but even if it were, the demo plane has flown in hot, humid conditions, with no operational problems, at many other places around the country. (including at least 4 years to OSH... which by the way requires flying right past Iowa ;) )

MartySantic said:
Some see the high oil temperatures and some, for some reason, do not. This population includes those in Florida and Texas. No one, to my knowledge has been able to explain this difference. I have one theory, but, have not taken the time to see if there is a correlation. The muffler can be moved forward and aft a bit before the bolts are tightened. This changes the distance between the 1200 degF muffler and the fins on the aft side of the oil cooler. I cannot put my small finger between the two components. It is close!!
Click to expand...

I hadn't thought about it before, but Marty might be on to something here.
As designed, the gap between the muffler and oil cooler is close... but no where near that close.
It is very possible, that if builders have chosen to deviate from the plans, and install their cowl with a gap larger than the nominal 1/8 ", every amount larger than 1/8" will likely reduce the gap between the cooler and muffler by an equal amount. Another possibility is a cooling air duct that was not trimmed as designed, and someone could easily end up with a cooler/muffler gap that is quite a bit smaller than intended.

One other explanation for high oil temps....
I believe there is at least one RV-12 builder, who after exhausting all other solutions, tried a different D-180 in his airplane and had no more high oil temp. indications.
 
Seek and you shall receive. Info that is!

This is a from the last page of a Formal Rotax document. Titled SI-912-016. It talks about suitable operating fluids to use in the 912.
rotax5017.jpg


Here is the web link if you wish to read the whole thing.
http://www.rotax-aircraft-engines.com/portaldata/5/dokus/d04899.pdf
So after reading the whole Document if I run Aeroshell Sport 4 I could easily fly with Oil temp at or below 248F with out any problems. I can occasionally operate above this temp. If I operate more than occasionally above 248F then I need to change my oil more often. So instead of saying green and yellow could you be more specific and say on a 60 min flight the max temp I reached was this exact number for this many mins. Rotax is very specific in what they say. Plus please look at all the other things already stated before my post. ;) I notciced that you are new to the form so welcome aboard and there is much good info to be learned here about the RV12 and the Rotax engine.:rolleyes: Here is the link to a long thread from last summer about oil temps.
http://www.vansairforce.com/community/showthread.php?t=73378&highlight=high+oil+temps&page=3
 
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Hi Randy, I think I can help you with this. BTW, I am the builder Scott referred to that had extremely high temps due to a faulty D180. After the replacement unit was installed, my temps were out of the red, but still higher than they should be. I initially felt that the clearance between the muffler and the oil cooler was the problem and that was correct. I did check all of the items Marty and Scott mentioned with negative results. I even developed a plan for another oil cooler mounted in series with the stock cooler. My thoughts always came back to that clearance. Mine was as Marty described, very tight. I performed my annual in Feb. and the winter months, as we all know, do not present a problem. During the inspection I decided to perform surgery on the cowl duct. Unfortunately I don't have pictures. What I did was actually very simple as I cut a section of the duct approx. 1 inch wide and removed it. I then moved the area of the duct that serves as the oil cooler mount forward approx. 1 inch and then re-glassed it in place and the problem was solved. If you look at my oil cooler from the outside, you can see that it is slightly farther forward because of this step-out procedure. I can now slide my whole hand between the muffler and the cooler. I hope to be at Osh with it next week and would be glad to show it to anyone that is interested. I have flown in 100 degree heat and during a Vx climb to 5K it only visited the yellow briefly. Lowering the nose brings it right into the green. I apologize for not taking pictures. This did truly solve my problem. Your opening statement described my feelings exactly, but it was something that just required a little cool thought and some trial and error to work out. PM me if you have any further questions and I will be glad to help.
 
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WOW!!! Thanks, Dave. I hope Scott takes note and Van's engineering implements your solution. This has been a mystery. The mystery may now be solved thanks to your effort!
 
MartySantic said:
WOW!!! Thanks, Dave. I hope Scott takes note and Van's engineering implements your solution. This has been a mystery. The mystery may now be solved thanks to your effort!
Click to expand...

Marty,
N412RV was built with the same parts that all customers get. It was built per the plans, and from the sounds of it has more clearance between the oil cooler and muffler than your airplane does.
It does not have oil temps any higher than expected when operating in hot OAT's.

I believe any RV-12 built per the plans will have adequate clearance between the muffler and the oil cooler for good performance in hot temperatures.
 
My experiences....

Keep in mind, I have less than 10 hours on our RV-12 but all the time has been flown in 90+ degree weather.

- I had high oil temps on my RV-10 and you will find this exact same thread over on the -10 forum. Lots of people jump to the oil cooler as the root cause but my experience on the -10 had more to do with controlling CHT's. I sealed every nook and cranny on the baffles and saw a 20 degree drop in CHT's which immediately lowered my oil temps. Not sure if this is an issue with the Rotax but when I installed my plenum on the -12 I made sure it fit very tight and I sealed around it every where so no air could leak out. I was very skeptical on the -10 when this was suggested but could not believe the difference.
We should share some data during a climb to not only compare oil temps but compare CHT's, airspeed, climb rates, RPM and oil temps.

- The muffler discussion might cause some differences. I know I shifted my muffler because the oil line coming out of the side of the engine was touching the front right exhaust. I moved it back so much that I had to cut a new hole in the bottom cowl and re-glass it. I now have around 1/2" - 1" between the exhaust and that oil line.

-Now, I have only flown single pilot so far but even on a 95 degree day, lower humidity here in Salt Lake, my oil temps hit about 235 and then settle out at 220 in cruise. My static RPM is 4950, about 5050-5200 in a climb depending on speed and OAT, and my max RPM is around 5600 WOT, level flight.

I would not be too worried about it yet as there are lots of things to look at and improve. Like others have mentioned, check the gap around the water cooler and ensure that no air can leak around it. Use RTV to seal around the plenum so air can only go through the fins of the cylinders, and check your prop for proper RPM and consistent pitch. I used a digital level and was able to get them within .1 degree. Without the level, using the build in system on the prop the best your will get is about 1.5 - 2.5 degrees between each blade which is so far off it is ridiculous.

I won't get it back for a couple of weeks from the paint shop to do more testing but will post some data to compare.
 
Texas

I live in the same neighborhood as Jetguy. My 12 now has well over 350 hours on it...most of it in the extreme outdoor temps of Texas. Due to personal preference, i like to fly high and enjoy the lower temps so I usually climb at 70kts till I feel comfortable then level off. Mine will enter the yellow at some point and well before it hits 248, it will start going the other way. As Marty and Scott both mentioned, the "gap" may be an issue. I do have a considerable gap in mine between the oil cooler and the muffler. I didn't do anything special, it just went together that way.

I will admit that if it is 108 outside and I decide to cruise around at 2000' full throttle I will see lots of yellow. That is if I can see through the sweat running into my eyes.
 
rvbuilder2002 said:
Marty,
N412RV was built with the same parts that all customers get. It was built per the plans, and from the sounds of it has more clearance between the oil cooler and muffler than your airplane does.
It does not have oil temps any higher than expected when operating in hot OAT's.

I believe any RV-12 built per the plans will have adequate clearance between the muffler and the oil cooler for good performance in hot temperatures.
Click to expand...

I in no way place any blame on Van's and I fully believe Scott knows this as we talked many times about this matter and has always been very helpful. I will agree that it could be an irregularity that was builder induced. That being said, it was time to go experimental and it worked this time. I do think that considering the amount of builders that have an issue with this, the f/g molding process of the cowl duct should be revisited and more clearance engineered into the duct. As we know, the engine plenum was very successfully modified a few years ago. BTW, I have not been holding out on the issue, but was waiting for high oat's to put it to the test before I shot my mouth off.
 
rvbuilder2002 said:
Marty,
N412RV was built with the same parts that all customers get. It was built per the plans, and from the sounds of it has more clearance between the oil cooler and muffler than your airplane does.
It does not have oil temps any higher than expected when operating in hot OAT's.

I believe any RV-12 built per the plans will have adequate clearance between the muffler and the oil cooler for good performance in hot temperatures.
Click to expand...

Scott:

I assure you that mine was built EXACTLY per the plans. I trimmed the cowl to the scribe lines before installing the engine and the cowl fit up turned out to be perfect. Had very good spinner alignment, which tells me the cowl is in the correct position. My spinner gap is at the minimum value (we had talked about it). The spinner gap being at the minimum tells me the oil cooler is as far forward as possible (relative to the firewall)??? .

I do know the muffler can be mounted and tightened in different positions fore and aft. This may be a determining factor. And may explain the difference between N412RV and N128MS.
 
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Dave12 said:
I do think that considering the amount of builders that have an issue with this, the f/g molding process of the cowl duct should be revisited and more clearance engineered into the duct. As we know, the engine plenum was very successfully modified a few years ago. BTW, I have not been holding out on the issue, but was waiting for high oat's to put it to the test before I shot my mouth off.
Click to expand...

I total agreement! This item should be revisited by Van's. Moving the position in the oil cooler by modifying the cowl would eliminate this nuisance. As proven by your mod and as mentioned by Scott, 2 responses previous.

Muffler position may also play a role as it can be moved fore and aft a bit. But that said, your modification truly displays the homebuilder BIG "E" in E-LSA.
 
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Several CT ownres seen 912s that run hot and some that run cold. Rare is it that we can figure out why. I never worry if I stay below 250 on climb out and 230 in cruise.

Things to check / try:

* Correct prop pitch - lugging the engine will increase oil temp
* Seal of radiator and oil cooler to cowling
* Wrap exhaust header with insulation
* Use full synthetic oil (ONLY if using mogas exclusively. If using any 100LL, use the Shell semi-synthetic.)
* Check sender and gauge calibration.

TODR
 
Hi Guys:

Yes, I repitched the prop.
Yes, I climb at 85kts.
Yes, my cowl is as far forward as possible with the absolute minimum gap
Yes, I checked the probe in boiling water
Yes, after sitting overnight all probes show the exact same temperature
Yes, I can stick my finger between the oil cooler and the muffler.
Yes, I use the aeroshell oil.

Haven't tried wrapping the muffler with insulation yet. What kind of "insulation" do you use?

I am really interested in seeing the modified cowl. But my oil lines are so tight that I don't see how I could move that oil cooler any farther forward. If there were some way of putting in a larger, thicker, oil cooler that protruded out into the cowl opening it could solve my problem. Does anyone custom build oil coolers?

Since it is going to be hot next week my dream of flying my shiny new airplane into Oskhosh looks unlikely. But, I will drive up on Tuesday so that I can meet with all of you guys.
 
Randy, You might want to contact Larry Baker in California before you try the insulation. He can relay his nightmare to you on the subject. Don't do it. Regarding your oil lines, the oil cooler is only moved forward 1 inch and if we are using the same lines, they should work fine. One more bit of advice, chill! I know this is a pain in the arse, but you will work through it. As I stated, I can slide my hand between the muffler and oil cooler. I am sending you a PM.
 
Looking into the air inlet to the oil cooler, notice that, around the perimeter of the oil cooler on 3 sides, the fiberglass is perpendicular to the airflow. I thought about reshaping the fiberglass so that air would flow straight into the oil cooler instead of hitting that lip around the perimeter. In addition, a streamlined fence could be fabricated on the left side of the oil cooler to help smooth the airflow both into the oil cooler and towards the water cooler. This is another one of those projects that I thought about doing but never got around to. Wouldn't it be great if someone made and sold a lightweight fiberglass shroud that would simply screw into place around the oil cooler inlet that would smooth out the airflow and cure the high oil temperature problems?
Joe Gores
 
For what it is worth, this oil cooler seems to have large capacity, positive airflow, and does a good job. Might be an acceptable alternative to the factory job.
30cafba.jpg
[/IMG]
 
For those of us with flying 12's I wonder if a different muffler would work. I experimented with heat shields 2 years ago with some success so I believe the close muffler has an effect on oil cooling. Titian Tornado has a muffler for the Rotax that is the size of a soup can. A new exhaust system would be a couple grand I would guess, but it would sure answer the question.
 
Geico266 said:
For those of us with flying 12's I wonder if a different muffler would work. I experimented with heat shields 2 years ago with some success so I believe the close muffler has an effect on oil cooling. Titian Tornado has a muffler for the Rotax that is the size of a soup can. A new exhaust system would be a couple grand I would guess, but it would sure answer the question.
Click to expand...

On this note, I considered modifying the rotax muffler prior to making the decision to modify the cowl duct, but it was just not prudent. I did price a new muffler just in case the modification was not successful and it was around $800.00. The cowl duct modification took only a few hours and the cost was about $20 bucks. BTW, I do have the written procedure and some diagrams of the mod. if anyone is interested, PM me your email address and I will be glad to send it. My temps are now in the green 99% of the time now. It was a big relief to me to see that this solved my problem.
 
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Any comment re this?

This comment came from a Rotax Repair Center.

Also wrap the muffler?

http://www.matronics.com/archive/archive-get.cgi?RotaxEngines-Archive.digest.vol-ar

Thermo-Tech is very common. You can pick header wrap up at places like Checker
auto, Auto Zone or Pep Boys. You need to get the 2" wide wrap and it is sold in
a 50' length. For the standard Rotax exhaust tube that is about 15" long you
need to cut a 68" piece. Dampen it. Don't soak it. It takes very little water
to moisten this stuff. You will need a hose clamp at the top and one for the
bottom. Start at the top or exhaust port and wrap 2 spiral turns then put the
first clamp on. Then spiral wrap all the way down. Only over wrap each edge by
about 3/8"- 1/2" and no more. If you over wrap too much it hold in too much
heat. When you get to the springs just go under them and wrap around the exhaust
knuckle. This will help with any exhaust blow-by. Do not over wrap the springs.
The springs need the cooler air. Once this is done apply the other clamp.
That's it, just do the other three like that.
If you have an EGT probe, do not wrap around this. The material in the cloth warp
interferes with the readings. It will make your EGT's swing 100F. Wrap up to
about 1/4" before the probe and add a clamp then start 1/4" past the EGT probe,
add a clamp and then on down. When your done let the engine run for 10 minutes
or so.

p.s.
When you start the engine for the first time it will smoke a little and smell like
it's burning. That will go away after about 10 minutes and the wrap will burn
and seat in place. It might give a faint burnt smell the first time out after
you shut the engine down. That's normal and don't worry. Once this has been
run a few times the wrap will be fragile so don't try and take it off and think
you can reuse it. If you scrape it hard with a tool it could abrade.

--------
Submitted by:-----
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
 
No clearance

Pulled the cowling to replace (hopefully) a bad EGT probe and like Marty, I can't get my little finger between the muffler and the radiator. Oil temp in the yellow arc by 3500 feet, 240's by 4500, and then drops back to 225-230 at 4500'+ cruise. Cruise at 3500' (Young Eagle flights) keeps temps in middle of the yellow arc. I think it's time for the cowling mod.

Wayne 120241/143WM
 
I flew the -12 to Pottstown, Pa. today and it was hot. Surface temps in the 90's. The oil temp never went out of the green. Before the mod, I would have probably stayed on the ground.
 
Jetguy said:
Dave lets see some pictures of your Mod?:confused:
Click to expand...

John

You can see the mods in person in a few weeks, he is only a short hop to KPTW. Dave flew over to help me with the final push to the DAR. I helps having a fellow RV12 builder looking over things.
 
Is there a way you could post these pictures? I am currently working on fitting the cowl and am about to install the oil cooler. If there's something I can do now to avoid high opil temps, I'd rather do it right away while it's easier to get at things....
 
Dave, I've sent a couple of PMs

Could you contact me offline at:[email protected].

I'd really like to see your drawings/phots/anything. I'd really like to get the oil temps down several degrees.

THANKS

Wayne 120241/143WM
 
RV12 Roger,

You asked for comments about header wrap and the article written by the person in Tucson. I know that person. He has considerable experience w/912's and has done numerous header wraps. mostly on CT's. He still swears by header wrap and I don't know of any of his customers being unhappy with having it done.

Having said that, it sounds like at least one person in CA had some problems but I don't know who did it and what the problems were.

So, do your research and do what you are comfortable with. I haven't done my CT probably because I am too lazy plus my temp problems went away when I properly set my prop.
 
yankee-flyer said:
Could you contact me offline at:[email protected].

I'd really like to see your drawings/phots/anything. I'd really like to get the oil temps down several degrees.

THANKS

Wayne 120241/143WM
Click to expand...

Wayne, I have responded to your request and also just tried to send to the email listed above to no avail. Do you have another email address?
 
HOT RV-12

I lowered my CHT from 238 deg on a day that was 91 deg at 2000 feet agl to198 deg CHT on a day that was 85 deg at 2000 agl. This to me is unbelivable. What I did was drain the 50-50 coolent from the engine and replace it with 100% distilled water, I added about 3 ounces of water pump lub. I have only flew it one time since I did this so I look fowarded to seeing if this is the new norm. Oil temp dropped also.
I was at the point of not daring to go more than guliding distance from the airport

HLS RV-9A and RV-12.
flying
 
Harvey L. Sorensen said:
I lowered my CHT from 238 deg on a day that was 91 deg at 2000 feet agl to198 deg CHT on a day that was 85 deg at 2000 agl. This to me is unbelivable. What I did was drain the 50-50 coolent from the engine and replace it with 100% distilled water, I added about 3 ounces of water pump lub. I have only flew it one time since I did this so I look fowarded to seeing if this is the new norm. Oil temp dropped also.
I was at the point of not daring to go more than guliding distance from the airport

HLS RV-9A and RV-12.
flying
Click to expand...

Harvey,

I think there is a very good chance that your fix was simply a Band-Aid for a different problem. I would suggest that you work to resolve the root cause of your high CHT's, so that you can go back to using the recommended coolant.
 
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