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Oil Temps in Winter too Low

rockwoodrv9

Well Known Member
Patron
I just did a 20 min flight out of KTEW - Mason MI. The outside air temp was between 20-30 degrees F. I did 3 T&G and one extended pattern.

I uploaded to SAVVY to check my oil temp. The highest it got was 119F. I had my heater on for 6 hours before I flew and the oil temp was 88 F when I started. My CHT were normal topping out about 390 on a full power climb just to get the temps up. Well, there was a 172 in the pattern too and I wanted to be at pattern height pretty quick so he knew what he was missing!

I have not covered any of my James cowl openings or aluminum taped the oil cooler. Other than that, what are my options to get the oil up hot enough to burn out the moisture? I have always had low oil temps and high CHT's.

Any ideas?
 
A search will bring up lots of threads and posts on this issue.

I've applied AL foil tape on the front side of the oil cooler so I can fold it up or down, depending on the season and how much of the cooler I want to cover. You may have to unbolt the cooler so you can get the AL foil tape all the way down to the bottom of the cooler, since the cylinder is in the way otherwise.

I'm on my second RV-8 in the Pacific NW. The first one had a parallel valve IO-360-A1A with 10:1 HC pistons and LASAR EIs. My current RV-8 has a parallel valve IO-360-M1B with a Slick IC Mag and an LSE Plasma III EI. Both airplanes have the oil cooler mounted behind Cylinder #4. Both airplanes have versions of Hartzell CS props.

Both airplanes have to have the front side of the oil cooler blocked off with AL tape to some degree to keep the oil temps between 165° F and 200° F in cruise.

On my current RV-8, in the winter most (~90%) of the front side of the oil cooler needs to be covered. In the summer, about 40% - 50% needs to be covered. My previous RV-8 was similar.

I found that blocking the backside of the cooler with a piece of AL plate bolted to the back via the mounting holes does not help much to increase the oil temp (~10° F), since air still flows around the tubes.

The minimum oil temp per Lycoming for continuous operation is 140°F. Desired oil temp is between 180°F and 190°F. I'm happy with anything between about 165°F and 200°F.

Hope that helps.

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I installed an oil cooler shutter on my RV-9A and it works great. I can close it off and the oil temps come right up to 180F+. About the coldest weather I see in the winter flights is mid-20's, so you guys in the frozen north may require a different solution.

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We’d rarely see temps here in Nevada that require us to worry about oil temps in the RV’s, but our Tundra is significantly over cooled, so in the winter, I use aluminum tape to hold a carefully engineered piece of aluminum (OK, it was the fist piece of scrap that came to hand….) over the oil cooler opening in the back of the baffles. Blocking it completely is too much, but allowing about a third of the 4” duct opening is about right.

I’d suggest adding a panel placard that says something like “Oil Cooler Block-off plate installed” to remind you remove it when it gets warmer…..
 
I installed an oil cooler shutter on my RV-9A and it works great. I can close it off and the oil temps come right up to 180F+. About the coldest weather I see in the winter flights is mid-20's, so you guys in the frozen north may require a different solution.
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Me too. Mounted between oil cooler and plenum, and on a Bowden cable so operative from the panel. For the first time ever I've been able to get oil temps above 120°F on a Minnesota winter day. I saw 200°F the other day with ambient temps at 20°F. Anti Splat.

..
 

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My shutter is mounted on the back side of the oil cooler. I don't recommend that location. To help boost oil temps and CHT I also put 3" wide strip of painters tape vertically across each cowl inlet.
 
Oil cooler airflow restriction....

My shutter is mounted on the back side of the oil cooler. I don't recommend that location.

My oil cooler is mounted to the engine mount with three welded fittings that makes it very stable and not subjecting the baffling to the strain of the cooler attached. I put a gate in the back to restrict airflow, adjustable from the cockpit. It is very efficient and there is a change in oil temperature depending on the position of the cooler gate. I do not have figures readily available as to the changes.

I also have to block the airflow to the cooler. There is a 2" fitting with SCAT hose supplying cooling air to the cooler itself from the baffling. As the temperatures drop, I have several blocking fittings that fit over the 2" fitting, the size depending on the OAT. The larger one I use with temperatures below 50-60 to maintain a reasonable oil temperature (170-180) I have a smaller one that I use from 70 and below. It stays open with temperatures above that. Works very well. OAT 75-85 travel logs show an oil temperature between 170 and 180 with it open, regulated by the back gate.

To help boost oil temps and CHT I also put 3" wide strip of painters tape vertically across each cowl inlet.

I need to do some experimenting with this as well as my CHTs usually run on the low side anyway, usually 250-300. Why we have EXPERIMENTAL on our aircraft.....
 

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I flew an hour today. Top oil temp was 136F. My CHT were normal in flight - except in decent they averaged about 365.

Tomorrow I will pull the cowl and plenum off and put a plate over the oil cooler. I have the antisplat shutter. I will see if I can install it. When I tried to install it on the outside of the cooler, it didnt fit with the bolts.

I dont want to cover the inlet much since I can get up to 400 if I hold a full power climb for too long.

If I cant get it up over 180, I will just change it more often to make sure I dont have too much moisture in it.

Question: Is it a good practice to open the oil dipstick after flight? Should it stay open or just for a few minutes? I have been opening it after I fly but want to make sure it is a good idea.

Thanks
 
IIRC, you have to drill the shutter to fit your cooler bolt pattern. I did find that on my application the bolts were just a little bit too short. Also…there was a flange on the upper and lower edges of the plenum opening that had to be pounded flat for the shutter to fit flush. Not a big deal, but not a drop-in either. In my case, it was really easy since I just had my A&P do it while he was doing the last CI.
 
IIRC, you have to drill the shutter to fit your cooler bolt pattern. I did find that on my application the bolts were just a little bit too short. Also…there was a flange on the upper and lower edges of the plenum opening that had to be pounded flat for the shutter to fit flush. Not a big deal, but not a drop-in either. In my case, it was really easy since I just had my A&P do it while he was doing the last CI.

To make the shudder fit the existing bolts, I would have to drill through parts of the shutter. It will work but didnt fit as I had expected it to. Maybe on the inside. Once I get the plenum off I will see if I can make it work. Last winter I just used aluminum tape on the inside of the plenum over the oil cooler and it helped - but still not as hot as I wanted.

I have a 90 degree oil filter adapter and wonder if that has something to do with how cool the oil is.
 
Yes, I did too but it wasn’t an issue. Allan mentions this in his video. Maybe your oil cooler shape is different than mine.

Thanks Mac. I will not let that bother me when I install it.

If you ever jump over the lake, come on by and say hello!
 
...

I have a 90 degree oil filter adapter and wonder if that has something to do with how cool the oil is.

That's an interesting question. I also have the 90 degree filter, which is where the temp probe is, and I have very low oil temps. Even when completely blocking off the oil cooler, it only helped by about 20 degrees, IIRC. I often wonder if those with low oil temp have something in common, and I had not thought of this.

About moisture in the oil, what I do is I use an engine dryer, the "black max". It seems to do the job drying the engine and keeping it dry, and no desiccant beads to mess with. However, parts on this thing fail regularly, but the gentleman that makes it (Ben) is helpful with replacements. Blackstone analysis never shows any water in the oil, not sure if that is actually meaningful or not in determining if there is enough moisture to cause corrosion in the engine.

I open the oil filler cap when I stop after a flight to let moisture out - Ed Kollin of Camguard fame said it can't hurt, and it will remove some moisture, so why not? Obviously don't forget to put it back before next flight!
 
That's an interesting question. I also have the 90 degree filter, which is where the temp probe is, and I have very low oil temps. Even when completely blocking off the oil cooler, it only helped by about 20 degrees, IIRC. I often wonder if those with low oil temp have something in common, and I had not thought of this.

90 adapter and with a 85* OAT I can only get the oil to 155 with the shutters open. Shutters are on the back of the cooler and stay closed most of the year in FL. Tape the front anytime below 50* to keep oil above 160. I have two oil temp probes and they align on the temp, so pretty confident on the data. I know I can move the shutters to the front of the cooler to make them more effective, but haven’t done that yet. With these settings, I have been able to keep the oil right around 175 during normal ops.
 
Rock, what oil cooler and configuration do you have?

Regardless of configuration, if hot weather sees high CHT and 180F oil temps, then you are using too much air through the oil cooler. I might say "ambient capability" is when the oil temp hits 220F in a 100 kt full power climb.

I use the same shutter, stock (small) Vans cooler (Niagara) and had good thermal management for CHT and Oil temp until I reduced my exit area. :eek:
 
Rocky, that cooler shutter from antisplat works even in negative temps out here. I can always get oil temp above 180.

As far as CHTs do you have pmags? If so you could try backing off the timing a bit, it helps a lot. First however, I would scour the baffles and seal any holes that air can escape/ not go through cooling fins.
 
This is interesting about the 90 degree adapter keeping the oil cooler. Im not sure if that is good or bad.

I have the standard 7 fin oil cooler mounted in the back corner of the baffles - standard. Today I removed the cooler and made an aluminum plate to cover the hole from inside the plenum to test. Im sure I will have to modify or try and fit the antisplat shutter somehow. I was going to go fly to try it out but it started snowing. Ugg MI weather. I will change the oil tomorrow now that the whole cowl is off and it has been 3 months.

I will get a picture of the oil filter adapter but it is pretty standard. Perhaps the engine oil is getting hot and the temp probe is in a location that isnt so hot? Maybe I need a second probe or move it to a different location. I cant remember where it is now but I will check tomorrow.
 

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Vernatherm valve

The engine has an oil temperature bypass valve. The vernatherm valve.
Provided that the oil has the right viscosity in relation to the outside temperature (see Lycoming oil SI), there is always a small flow through the
oil cooler. To thick oil and cold outside air temp will result in no flow trough
the cooler. The vernatherm valve is normaly open to the engine and when the oil temperature reaches about 185F the valve starts to close, forcing oil through the oil cooler.
Before starting construction work on the installation, it is recommended to
check the function of the vernatherm valve.
Remove the valve and put it in hot water.
The change in length from room temp to 185F should be .19", and at 200F .24".

Good luck
 
. Perhaps the engine oil is getting hot and the temp probe is in a location that isnt so hot? Maybe I need a second probe or move it to a different location. I cant remember where it is now but I will check tomorrow.

Little to be lost by installing the Anti-splat shutter, especially since you're already at that point. Mark the holes, drill them, flatten the lips on the plenum at the opening (you might need longer bolts). If you don't mind operating the shutter manually, you don't need the Bowden cable and its firewall pass-through, but I find that to be a really convenient part of the device.

The question of temp sensor location is important, I think, as is proper vernatherm function. I was/am suspicious that my temp sensor's location may not be entirely reflective of the actual oil temp where it counts, so I waffle a bit in controlling the shutter. Attached are some Lycoming documents that might be helpful, and a shot of my oil temp sensor on the firewall. Seems likely that the temp of the oil there would be cooler than the temp actually in the engine.

..

SI1008C%20Bypass%20Valve%20Installation.pdf
 

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... I was/am suspicious that my temp sensor's location may not be entirely reflective of the actual oil temp where it counts, so I waffle a bit in controlling the shutter. Attached are some Lycoming documents that might be helpful, and a shot of my oil temp sensor on the firewall. Seems likely that the temp of the oil there would be cooler than the temp actually in the engine.
...

If that really is your oil temperature sensor - which I kind of doubt - then it would not be reflective at all of your actual engine oil temperature. I think that's a pressure switch to perhaps drive a hobbs meter or an oil pressure warning light?
 
The question of temp sensor location is important, I think, as is proper vernatherm function. I was/am suspicious that my temp sensor's location may not be entirely reflective of the actual oil temp where it counts, so I waffle a bit in controlling the shutter. Attached are some Lycoming documents that might be helpful, and a shot of my oil temp sensor on the firewall. Seems likely that the temp of the oil there would be cooler than the temp actually in the engine.


I suspect this is your sensor layout, upper photo

Typical Oil Temp sensor location, lower photo
 

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If that really is your oil temperature sensor - which I kind of doubt - then it would not be reflective at all of your actual engine oil temperature. I think that's a pressure switch to perhaps drive a hobbs meter or an oil pressure warning light?

Ooh! Well that's certainly a possibility. I would have had no clue! Decades ago I was a factory-trained MOPAR mechanic but apparently a 1969 Hemi 440 6-pack has little in common with a modern Lycoming airplane engine! Who knew?

When I get a chance, I'll go on a hunt for the temp sensor, out of curiosity.

Good tip!!
 
I need to check my temp sensor location too. In my head I couldn’t imagine the oil being as cold as shown. Thanks for the discussion. It may have saved me a problem!
 
Try slow flight to heat up your oil. Despite the low power setting flight at 55-60 kts causes my RV-6's oil temp to exceed 180 degs within 10 mins or so with OATs below freezing.
 
I removed the plate I made yesterday to cover the oil cooler inside my plenum and cut some wedges out of it. My temp sensor is shown as coming out of the back of the filter adapter. I dont know if that makes the reading lower than a different location so I didnt want to completely cover the cooler so I cut the wedges.

I flew for an hour today. About 25 degrees and my oil temp got up to 167. It could have gotten up higher but I forgot to bring my sd card with me today.

I am happy with that. I changed the oil today and will send it to Blackstone and see what they say.

I dont think it will be flying weather until the weekend but I will try slow flight and make sure I bring my sd card to see if I can get the temp up higher. Thanks for the help.
 

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