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RV-12: Summer Oil Temps

Geico266

Well Known Member
As I fly the -12 in the heat of the midwestern plains this summer I am beginning to see oil temps that are approaching concern at moderate to high engine RPMS. While never in the yellow or red these temps are around 230F. The Shell Oil lubrication engineers I’ve talked to say you can run the oil at these temps with no issues, and Rotax says these temps are fine, but I would like to see them lower. The purpose of this thread is to document oil temps in the RV-12 and "solutions" to reduce summer operating oil temps.

The first step was to take Scott's advice and take a real close look at the bottom cowl cooling plenum radiator seal. The theory is by keep the air pressure high in the cooling plenum this increases / maintains airflow through the oil cooler. Okay, that sounds good, so I “tighten it up a little” and added more weather stripping on the bottom. The results were measureable and it reduced the oil temps by about 4 degrees F, but I was looking for something better.

Before we get going with the mods here are the current numbers after additional weather stripping.

4,800 RPM, OAT 75F, Oil temps: 207F
5,000 RPM, OAT 75F, Oil temps: 212F
5,200 RPM, OAT 75F, Oil temps: 220F
5,400 RPM, OAT 75F, Oil temps: 230F

A theory I have is radiant heat from the muffler is diminishing the cooling capacity / efficiency of the oil cooler. The muffler is about 1 1/4” away from the oil cooler. As I understand it, and in talking with qualified engineers air flow does not reduce the effect radiant heat has on an object. I decided to add a fiberglass heat wrap barrier to the muffler.

RV-12_Oil_cooler__Muffler__Medium_.jpg


The above picture shows the muffler proximity to the oil cooler.

Here are the results of the test after the heat barrier was installed.

4,800 RPM, OAT 75F, Oil temp: 195F
5,000 RPM, OAT 75F, Oil temp: 209F
5,200 RPM, OAT 75F, Oil temp: 215F
5,400 RPM, OAT 75F, Oil temp: 222F
5,400 RPM, OAT 85F, Oil temp: 230F

It appears I might be onto something here as the temps are definately lower with just a minimal amount of exhaust wrap. I will post the results of further Non-Van Aircraft Approved Tinkering. :D I would like to try a heat sheild, but getting to close to the oil cooler could only diminish the airflow. I can see some serious tinkering thinking is in the future! :rolleyes:

Here is a link to the material used. http://www.aircraftspruce.com/catalog/eppages/graphblkwrap.php

RV-12_Muffler_Wrap__Medium_.jpg



Do not use a product like this http://www.jegs.com/i/Thermo Tec/893/16850/10002/-1?CT=999
as it will not take the 1100F as advertized. Ask me how I know. :mad:


Your mileage may very. ;)
 
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Oil Temps

Down here in Texas while doing the 75kt climb to 10,000 feet we saw oil temps up to 233F at 4700rpm.
2000feet OAT 82F AS 75kts Oil Temp 230F
4000feet OAT 71F AS 75kts Oil Temp 237F
6000Feet OAT 68F AS 75kts Oil Temp 230F
8000Feet OAT 61F AS 75kts Oil Temp 227F
RPM Constant at 4700RPM
Oil Pennzoil Motorcycle oil
John
RV12 N1212K
 
Larry,

Happy to hear the results. Our theory that the radiant heat from the muffler is contributing to higher than "we would expect" oil temperatures appears to be true.

I also took the advice of Scott McDaniels and purchased a new length of the weatherstrip from Van's and installed it on the water radiator interface. I had originally installed a thinner weatherstrip to make lower cowl installation easier. I also measured, the gap and found the gap to be 1/4" per the plans. This did reduce my oil temperatures a bit.

Like we have discussed, I am seeing similar oil temperatures as you are seeing. Without your suggested insulation wrap, I can easily get to an oil temperature of 220-230 deg at 5300 rpm with an OAT of 75-80 degF.

Via my phone conversations and some side by side flying, I am also aware of 6 other flying RV-12's that are also experiencing very similar "higher than one would expect" oil temperatures. I only know of one (Pete Anderson) that appears to be experiencing lower oil temperatures (similar to the oil temperatures Scott McDaniels has mentioned we should expect, ie., 205 degF for the stated flying conditions.) So it seems this "higher than expected oil temperature" appears to be the norm and not the exception.

Sure would like to hear from the other flying RV12s builders as to the oil temperatures they are observing with the summer weather. Please state engine rpm, OAT and oil temperature observed after at least 10 minutes of level flight at the power setting. It takes 10-15 minutes for the oil temperature to stabilize.
 
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Cooling duct turbulence

Looking inside of the Cooling duct, there must be turbulence from the 90 degree turn that the air has to make around the perimeter of the oil cooler. A fairing from the cowl opening to 3 sides of the oil cooler would get rid of that 1" lip and smooth the air flow into the oil cooler. Also the lower edge of the cowl opening has a sharp edge. If that edge were rounded and extended to the bottom of the oil cooler, it would help too. Each little bit of "Tinkering" could help by a few degrees.
Joe
 
I looked at my data log from flying the test cards and the highest oil temp reached 250? for a 6 minute period between 5800' and 9500' during the sustained climb to 10,000'. Running the oil at 250? for 6 minutes doesn't concern me.
But what does concern me is moisture in the oil. When an engine cools down after running, air is pulled into the system. On the Rotax the oil tank top is not sealed and there is a vent. In my part of the country that air is full of moisture introducing water into the system. Personally, I want to see oil temps above the boiling point of water. Water in the oil is going to do more damage than oil temps in the 230-250? range, IMHO. 230? is OK, 250? is hot, 270? is too hot.

I can't offer any meaningful level flight oil temp data for summer heat operation, because we don't have that here much :(.

BTW, the data logs are very cool. You can see everything that the EFIS and EMS displayed on a second by second basis. It is really a good idea to have that data connector routed to an accessible location so you can download the data logs, modify checklists, upgrade firmware, etc.

Tony
 
I agree with Tony about water in the oil. Water mixes with the hydrocarbons and sulfur in the oil, producing acid. Temperatures above boiling are good. Thats why the old car with low mileage that the little old lady just drove church each week is not such a good buy. She never got the oil warm enough to boil off the water.

I'm concerned about the high temperatures some -12 drivers are seeing. The POH states the normal operating temperatures as 190F to 230F with 248F as a red line. It seems Van's needs to address this problem as it violates their recommendations.

I wonder if the proximity of the muffler was intended to assist warming the oil to allow engine RPMs above 2500?

Art Pennanen
 
Larry

Pete is just so cool his oils temps are too


Larry has discovered my secret! lol.

I told you guys not to throw the instructions in the trash but nooooo....you all said, "I don't need no stinkin rules."
 
Oil Temps

We are also seeing high temps as it warms up in California. Cruising is not too bad but climbing is. It is difficult to climb to higher than 3500 or 4000 without getting uncomfortably in the yellow (240). To get higher we have been leveling off to cool and then start climbing again. By the time we get to cool air all is well again. At 8500 ft and 5500 rpm it is about 235 F. Not bad but it is hard to get there. I have not been logging specific values but I will.

Is the muffler rap strips of material that go around and overlap? How much does it take? I have been concerned about the proximity of the muffler to the oil cooler. I don't think that is the only culprit. My partner and I also have a Murphy Renegade (biplane with Rotax 912). The oil cooler is not by a muffler and it gets hot as well. Maybe just part of the engine.

I am planning on going to OSH this summer and now wondering about getting over the mountains in Montana. I know the factory airplane has done it a couple of times and don't recall any issues being posted.

Rich
 
It's interesting that Rotex's Operating manual shows the same 190F to 230F normal operating temperature range, but allows a red line of 266F while Van's only allows 248F.

Art Pennanen
 
Been doing some flying in 80 degree weather and I am now seeing the same thing (higher temps about the same as others have reported). I also talked to another RV12 owner who called me a month ago concerned about the higher temps he was seeing in 75 OAT.




Brad Stiefvater
110 hours on the 124BJ now.
 
Thanks guys for the feedback. Keep it coming. It would sure be nice to know what Van the man is seeing with respect to oil temperatures. The red RV-12 (Van's A/C) differs a bit from our RV-12s just looking at the under the hood pictures from Oshkosh 2009.
 
I decided to remove the exhaust wrap and build a heat shield out of .024 aluminum. I removed the muffler by taking off the 4 springs and made a heat shield that would fit over the inlets. I used aluminum pop rivets to make 1/4" stand offs all the way around the heat shield and held it in place with the 6" clamps. I also cut 5 1" "louvers" in the forward edge of the heat shield to allow high pressure air coming though the oil cooler to circulate around the muffler. This helps cool the heat shield reducing radiant heat.

Here are the results of the test run.

OAT 78F

4800 RPM = 195F
5000 RPM = 210F
5200 RPM = 217F

As you can see the heat shield did about the same results as the heat wrap, and the heat shield will not accelerate corrosion that is possible with the wrap.


IMHO this is a cheap and easy fix to reduce summer oil temps in the RV-12.
 
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In talking with Pete and Marty we feel the difference in Pete's "low" temps (we still think Pete is cool ;) ) and our "high" temps is humidity. Can someone here with a heat transfer engineering background speak to the effect the humidity has on heat transfer through a radiator, and radiate heat transfer? Does humidity increase radiate heat transfer?
 
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Hi Larry,

You know, here in Florida we got humidity and lots of it and we sure got the high oil temperature too.

As you always tell the first flight guys we need to see pictures of your new heat shield. It does sound like a good idea.

Best regards,
Vern
 
Hi Larry,

You know, here in Florida we got humidity and lots of it and we sure got the high oil temperature too.

As you always tell the first flight guys we need to see pictures of your new heat shield. It does sound like a good idea.

Best regards,
Vern

:eek: I forgot my camera! I'll take pictures of it soon! I want to put another 3-4 hours on it and take it apart for inspection and build a permanent one. The one I built today is pretty crude as I didn't have access to a sheet metal roller, but it still works! I think I'll use stainless steel on the permanent one.


Basically it is a shield that goes around the muffler with 1/4" stand offs and slots to allow a little air flow. It's a good way to knock 15F off the oil temps! :D
 
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If your oil temps run hot, consider using the Shell Aero Sport Plus 4 semi-synthetic oil. Rotax specifically approves it for use with 100LL and it will last longer if you run at high temps.

Also, check out the latest Rotax service instruction on oil selection. They list 266F as the redline. My S-LSA has a yellow range from 230-266F. We try and keep the temps below 230F, and it's a challenge in the summer. Cruise-climbs are the norm.

The insulating wrap on the header and muffler has helped many CTs in reducing oil temps, probably from reducing radiant heat from the exhaust.

TODR
 
TODR, Any thoughts on corrosion using the wrap? I've been told by a Rotax service guy that he was working on a wrapped exhaust system and he could put his finger through the side of the muffler. I have no idea how old it was, but he seems to think the wrap caused the corrosion to accelerate. Also, the wrap can hide cracks..... not a good thing... so it should be removed and replaced every annual?
 
More info

I have a friend who has a master's degree in Engineering. He told me a metal shield between the muffler and oil cooler was far superior to a heat wrap on the muffler, for reducing radiant heat transfer to the oil cooler. He said humidity has less ( little ) affect on cooling. We don't want to block air flow, so a rounded shield placed closer to the muffler will likely give best results.

John Bender
 
Humidity

One of the things high humidity does is make the air less dense since water vapor is lighter than the other constituents of air. That's why it is necessary to lean your engine for take-off when the humidity is high. Humid air, being less dense, does not carry the heat off as well. However, the engine puts out less power in humid air, so the engine doesn't run as hot. BTW, the humid air also lessens wing lift and prop thrust, so besides having less power, your takeoff will take more time and distance.
 
It would sure be nice to know what Van the man is seeing with respect to oil temperatures. The red RV-12 (Van's A/C) differs a bit from our RV-12s just looking at the under the hood pictures from Oshkosh 2009.

There are only two very minor differences.

The mounting location of the fuel pressure sensor and the brake fluid reservoir are reversed.

Everything related to the cooling system (both heat exchangers, air duct, radiator seals, etc.) are the exact same parts that all kit builders received and they are all installed in accordance with the construction manual.

N412RV has now made two round trips to OSH from Oregon (08 & 09, flown at the peak of the summer heat). I personally flew 3 of those four trip legs. When flying cross country I always cruise climb when able, but when I couldn't (like climbing out of Caldwell ID) I still never had the oil temps exceed 230 F in the temps I have flown it in. I am confused why some RV-12's are seeing oil temps exceeding 230F and others are not.
 
Has anyone correlated the coolant difference between the hot & cool engines... if any? Are the cool engines using Evans? Are the hot engines all on Dexcool?

-Ron
 
Oil Temps

Ron this thread is about Oil Temps not CHTs or Coolant Temp. Althought the CHTs could affect Oil temp I think Most CHTs a in the normal Range.
John
RV12 N1212K
 
Texas Oil Temps

John,

As my other North Texas 12 flyer...I flew from Pecan today to RedBird (50nm) at 2500' at 5300 RPM and my oil temps stayed 195 to 210. Now on climb out I have to cruise climb at 90/95 or my CHTS will hit 230plus. What are you seeing? I know you're probably flying off your card so its probably awful with those 65kt climbs!
 
Oil Temps

Larry and Pete,

Pete I'm seeing the same thing. Larry what do you think about this scenario. We enlarged the fiberglass opening in the cowl that the oil cooler fits into. But how about the aluminum plate that goes in the front of the oil cooler, part FF-1214, see page 49-09. It looks like this part could also be enlarged to let even more air though. Did anybody open this part up beyond the stock size as it comes out of the shipping box? Maybe we should start a survey. Seems to me that at least 70% of the flying RV12s are having High oil temps from this thread.
John
RV12 Flying

PS Pete did you do the Dynon software Update Yet?
Send me an email on how it went.
 
John,

As my other North Texas 12 flyer...I flew from Pecan today to RedBird (50nm) at 2500' at 5300 RPM and my oil temps stayed 195 to 210. Now on climb out I have to cruise climb at 90/95 or my CHTS will hit 230plus. What are you seeing? I know you're probably flying off your card so its probably awful with those 65kt climbs!

Pete,

We having been joking before. BUT, your oil temps and CHTs aperar to be reversed.
 
Oil (and updates)

Marty,

You're just jealous. Their are 50 some completed 12's. I haven't seen 35 complaints on here. Van's certainly has not received 35 complaints. So my airplane works as advertised...my IPhone4 doesn't! Feel better!

John,

We went on vacation and since then I've been looking for a PC laptop to do it with (Dynon doesn't do Apple). Did you get it to work?
 
Okay, as requested here is my muffler heat shield. I think it is better than the muffler wrap due to corrosion, weight, and not being able to see cracks.

Here is a visual list of materials. Anyone remember the Popular Mechanics projects?

The metal used is .025 aluminum sheet cut to 14 1/4" x 19" and rolled at a local shop to 6" diam.

RV-12_Materials.jpg

The muffler is easily removed by removing the 4 springs, and gently prying it out. You may have to listen the exhaust bolts. The yellow paper on the muffler is a template.

Here is the finished product.

RV-12_muffler_shield.jpg

The dark lines are where I will cut and bend a "louver" to allow air flow from behind the radiator to cool the inside of the heat shield. The shop head side of the pop rivets act as the 1/4" stand off. Crude I know, but it reduces the oil temps 8-15F at 80F OAT.

RV-12_Shield_Installed__Medium_.jpg


Notice the slots behind the oil cooler to allow airflow between the muffler and shield. Also, I used some of the old fiberglass wrap to insulate the oil cooler fittings.
 
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Their are 50 some completed 12's. I haven't seen 35 complaints on here.

I have not tried to contact EVERY builder that has a flying RV-12, but for the dozen or so I have been able to talk to either by phone, face to face or via e-mail, all express concern seeing "higher than expected" oil temperatures with you being the ONLY exception. That is something I cannot explain.

This may also boil down to what "higher than expected" really means.
 
I have seen oil temps as high as 230 on climb out on 90 degree days - drops back to 220 and stays there at cruise at low altitude with the high OAT.

Last Thursday I flew 11.5 hours from KY to SD and back. My last leg, I departed with a ground temp of 82. Climbed to 7500' at 85 knts where it was 59 degrees. Max, steady oil temp on climb was 216. Level at 7500, oil temp stayed around 205.

Is this 'higher than expected' ?
 
I have seen oil temps as high as 230 on climb out on 90 degree days - drops back to 220 and stays there at cruise at low altitude with the high OAT.

Last Thursday I flew 11.5 hours from KY to SD and back. My last leg, I departed with a ground temp of 82. Climbed to 7500' at 85 knts where it was 59 degrees. Max, steady oil temp on climb was 216. Level at 7500, oil temp stayed around 205.

Is this 'higher than expected' ?

In talking to Ronny Smith, South Mississippi Light Aircraft / Rotax Service Center that your temps are fine. Climb out temps to 260 and settling back to 230 on cruise is totally acceptable and normal according to Ronny. Run a good semi synthetic oil and change it when due. I have been able to lower my temps slightly with the heat shield by an average of 8-15F.
 
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Having flown Rotax 912s for a while (albeit not on an RV12, yet :) ), I can say that 230F is absolutely fine. In fact, I would be so bold as to suggest you chaps are lucky as I have flown a number of 912 installations where I have had to struggle to reach the normal operating temperature range. The Rotax 912ULS manual states that max oil temp should be 285 and the normal range is 190-230. As previously stated, it is also recommended that oil temp reaches at least 212 at least once a day to address the condensation issue.

CHTs should not exceed 300.
 
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Having flown Rotax 912s for a while (albeit not on an RV12, yet :) ), I can say that 230F is absolutely fine. In fact, I would be so bold as to suggest you chaps are lucky as I have flown a number of 912 installations where I have had to struggle to reach the normal operating temperature range. The Rotax 912ULS manual states that max oil temp should be 285 and the normal range is 190-230. As previously stated, it is also recommended that oil temp reaches at least 212 at least once a day to address the condensation issue.

CHTs should not exceed 300.

I'm beginning to understand that the temps we are seeing are perfectly fine. :D

Time to go fly!
 
I just found this thread. I just flew a round trip from SW Washington to the Mts. of Idaho. Climbing out from 800' in Washington with OAT around 80 degrees, I cruise climbed at 95 kts and still had oil temps up to 244. The temps remained at 230 - 233 even above 8000', but the OAT's remained at 80+. On the return trip starting at 5000' with OAT 0f 68 - 72 degrees, I was always at 227 - 233 degrees until let down. I was a bit concerned with the high (to me) oil temps due to the relatively low OAT's for summer time -- I was in the air by 6-7 a.m. If I were leaving in the heat of the day at around 90 degrees, I think my oil temps would have been at red line.

Geico266's mod looks interesting. I'm thinking that by trimming the back of the aluminum shield to clear the exhaust header connections to the muffler, you'd be able to remove the shield without having to undo any springs. It looks like I have about 1 1/2" clearance right now, so the shield should help.

Since this thread stopped almost three years ago, any follow up with the heat shield -- any problems?

TIA

John
 
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