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Oil temperature question

Yup, it's not pretty. But any corrosion is limited to the tip itself, so I've been putting it off.
 
I had some time this afternoon so I went to the hangar! After I realized I forgot my compression tester again I decided to go flying for some more data:


Segment 1:
5,500 ft (30.45)
134 mph IAS
38 deg F OAT
2350 RPM
CHTs: 284, 308, 315, 314
OT: 185 deg F
Delta P: 4.2


Segment 2:
3,500 ft (30.44)
135 mph IAS
51 deg F OAT
2450 RPM
CHTs: 295, 325, 325, 324
OT: 185 deg F
Delta P: 4.2


Segment 3:
4,500 ft (30.43)
135 mph IAS
46 deg F OAT
2450 RPM
CHTs: 304, 317, 331, 325
OT: 185 deg F
Delta P: 4.2


Looks like the old vernatherm is doing its job now. CHTs are super cool... I'm curious what other cowl designs really see for delta pressures. Lycoming wants 5 inches of water difference between the top and bottom of the baffles, but I'm having a hard enough time keeping the CHTs up at 4.2 inH2O!


I'm going to leave my sheetmetal duct on there for a while, but when I feel ready for another challenge I'm going to try glassing it in permanently!
 
Had another fun flying day. I still haven't done the automotive compression test, but this time was because the OAT appeared warmer and I thought it'd be more fun to enjoy the day and get a good data set instead of spending the day in the hangar.


Segment 1:
2,650 ft (30.15)
132 mph IAS
59 deg F OAT
2250 RPM
CHTs: 297, 314, 325, 320
OT: 190 deg F
Delta P: 3.4


Segment 2:
3,000 ft (30.14)
110 mph IAS
53 deg F OAT
2000 RPM
CHTs: 293, 307, 319, 316
OT: 181 deg F
Delta P: 3.0


Segment 3:
2,000 ft (30.15)
120 mph IAS
61 deg F OAT
2100 RPM
CHTs: 297, 312, 324, 320
OT: 189 deg F
Delta P: 3.3


Still looking ok. Super cool CHTs still. Oil temps well within limits, OAT is still very cool. I'm looking forward to seeing what they do with warmer OATs. Plus its been really nice to just fly the damn plane, haha!
 
Did some maintenance today, pulled and cleaned all the plugs and reinstalled them in the same cylinders, but swapped bottoms and tops. I also did an automotive compression test (cold, I ran out of time to do it hot as well - 122, 120, 125, 123). After that I buttoned it all up and went flying for about an hour to top off the tanks for this upcoming weekend and to warm the oil before I changed it.


Some spark plug images:
#2 bottom
74D3CC60-2B57-4ADC-8A82-5676D3C0CCDC_zpsxdlyvads.jpg

#4 top
C2326CEA-8728-4BBB-A11E-9139FE9B60CA_zpswtkku2zg.jpg

#1 bottom
EF63A02C-7C62-408B-A8B9-258882EF728E_zpss33e4dm5.jpg

#3 bottom
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I tried to look at the valves but I couldn't get a good angle through the spark plug holes with the non-articulating head on my boroscope. I might try to borrow one from work one of these days just to see how they look.


Just for completeness I pulled the viscosity valve plug and ran a magnet down there - returned nothing. I did this before the flight, and didn't think to look in there after the oil had all been drained. I had also meant to pull the oil filter adapter on this oil change and see if there was anything funky going on with the gasket, but I forgot to order a new one and couldn't get to that.


But I did try to use my boroscope to look in the oil filter adapter while I changed the filter and came up with these:


Vernatherm! This is from the left-most hole in the area the filter covers as viewed from the back of the engine.
61DB053B-EFE7-4123-A878-A76556B2C66A_zpstz5q4ori.jpg



The thing on the left appears to be the pressure relief valve. Second pic is the same area, just moved to a slightly better angle to see the thing. Also, should any of this be . This is from inside the part that the filter actually screws into.
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4383C66A-2813-40B9-B0A3-E17E4A421737_zpspfb3me7h.jpg



I think this is the face of the pressure relief valve. This is from the right-most hole in the area the filter covers as viewed from the back of the engine.
74DCD261-68D6-4475-BA8C-DBED52116B65_zpsmgaep8m1.jpg



Anyways, I changed the oil and took a sample that'll go out to Blackstone Labs tomorrow morning. Then I added some MMO to the fuel and buttoned it all up for the night.


Some data points from my oil warm-up flight:


Segment 1:
2,400 ft (30.05)
139 mph IAS
70 deg F OAT
2475 RPM
CHTs: 320, 333, 345, 338
EGTs: 1305, 1334, 1301, 1364
OT: 200 deg F
Delta P: 4.1


Segment 2:
1,800 ft (30.05)
138 mph IAS
73 deg F OAT
2400 RPM
CHTs: 326, 341, 354, 345
EGTs: 1313, 1346, 1310, 1368
OT: 210 deg F
Delta P: 4.1


I did notice that my EGTs on #2 and #4 were oscillating up and down about 5-8 degrees. I don't usually watch them, so I don't know if this is normal. It ran the same as it always has - very well except higher oil temps that I would expect.
 
SJ,

It won't let me add the part before "//" to my image links. It keeps telling me "Post denied. New posts are limited by number of URLs it may contain and checked if it doesn't contain forbidden words." Can you fix this so I can make my pictures post?
 
Haven't done the hot auto compression check yet but its on the list. I have made a few flights and OTs are still higher than I'm happy with.


No changes to anything except an oil change.


The oil after 4.9 (cold reading, thicker oil) and 8.3 hours of flying (hot reading, thinner oil) are attached, in order.
4.9 hr Oil.jpg8.3 hr Oil.jpg


All of these hours have been cross country with engine conditions from 2450-2500 rpm, CHTs 310-360 deg F (I've got a ~25 deg F spread between my coolest (#1) and my hottest (#3)), and OTs ~220-230 deg F. The speeds I'm seeing give me between 3.5-4.2 inches of water pressure differential between the upper and lower baffles, measured from the top of the engine case and behind the oil cooler.


Something interesting that I noticed on yesterday's flight was that the OT appears to be RPM related somehow. Looking back through my data I can see a trend as well, but nothing that I had noticed before. We were in cruise (2450 rpm, OT 230) and there was a headwind at 5,500 ft. So I nosed it over (changing nothing else but pitch trim and accepting the airspeed increase and ~2600 rpm it gave me) and started a descent to 3,500 ft. At about 4,000 ft I noticed that OT was heading up to 235, so I pushed the mixture in a bit. CHTs were below where they had been at 5,500, which makes sense because the cowl delta P would be higher from the increased airspeed. OT ended up peaking at 238 as I leveled off at 3,500 ft, so I pulled the RPM back to 2350 and readjusted the mixture to get CHTs from 315-340 and OT settled back out at 230 again. I'm not sure what would cause that.


Oil looks good, breather bottle hasn't changed. There's a little more oil around the oil pan where the dipstick tube connects, but I don't think blow-by is the problem. I'm still going to do a hot automotive compression test to try and rule it out, but otherwise I think I'll be back to working on airflow.
 

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Also got my oil analysis back - Iron, Aluminum, and Nickel were a little high, but nothing that they thought couldn't be attributed to some of the periods of inactivity that I had last year.
 
Just closing the loop but I fixed the problem. I moved my oil cooler to the firewall (fed with 4” SCAT) and installed my pmags as well as some minor maintenance to my exhaust and baffling. I think baffle mounted oil coolers can work well, but my particular integration didn’t allow the right geometry.

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Upper to lower cowling pressure differential hasn’t changed significantly, but oil temps are down over 40 degrees in similar OATs from when the cooler was mounted on the baffles.

Looking forward to seeing how it does this summer.

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OATs were ~55 deg F.
 
Thanks for the follow-up. It surprises me that there was such an improvement from remote mounting the cooler while drawing the air from the same spot. How did the CHT's respond to the Pmags? I'm sure they're down somewhat. Cruise economy has to be better also.
 
Thanks for the follow-up. It surprises me that there was such an improvement from remote mounting the cooler while drawing the air from the same spot. How did the CHT's respond to the Pmags? I'm sure they're down somewhat. Cruise economy has to be better also.

I was actually able to raise the 4” opening for the SCAT higher than the oil cooler could mount. In fact, it’s nearly completely above the cylinder and I made a small baffle to separate where they overlap. I think that was the big difference. Almost 3/4 of my oil cooler was flush against the cylinder fins. I wouldn’t have thought that was a problem until I had terrible oil cooling.

Old:
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New:
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My theory is that I was only getting air flow through 1/4-1/2 of the oil cooler - the top part.

Pressure differential is the engine that drives air cooling. I think that as the air accelerated downward through the cylinder fins next to the oil cooler, it dropped pressure (Bernoulli’s principle), and there wasn’t enough pressure differential to accelerate that air aft into the lower part of the oil cooler.

But that’s just my guess.

I also have the added benefit of not having to rebuild any cracked baffles from here out, but I could have reinforced them better to prevent those even with the oil cooler mounted where it was.

CHTs are actually up with the pmags! I had forgotten that was probably going to happen, I’d read that since the engine was making more power at part throttle due to the ignition advance CHTs would increase. I was a little surprised until I thought about it and remembered, haha.

They’re up about 15-20 deg F from similar conditions with the bendix mags. Not bad at all. I’ll see how they look in the summer and make more cowling adjustments if I need to.

Unfortunately I don’t have fuel flow indications, so I’ve got to wait to figure the new fuel burn, but I was going faster for the same RPM as I had in similar conditions with the bendix mags.
 
I think that new baffle has a lot to do with your results. With the original arrangement, the cooler was picking up a considerable amount of heat from #4 cyl. head. The baffle is directing the hot air down/around the head and out the bottom, so the cooler is getting its own supply of un-heated air. The baffle probably would have solved the problem by itself BUT, rear mounted coolers always seem to take their toll on the rear wall of the box, even with a doubler. That's a very nice installation, ya' done good!

P.S. -- Don't go throwing around things like "Bernoulli's principle". Before you know it, Gordon will be in here muddying up the water with all his physics. --- waiting.....waiting.....
 
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I think that new baffle has a lot to do with your results. With the original arrangement, the cooler was picking up a considerable amount of heat from #4 cyl. head. The baffle is directing the hot air down/around the head and out the bottom, so the cooler is getting its own supply of un-heated air. The baffle probably would have solved the problem by itself BUT, rear mounted coolers always seem to take their toll on the rear wall of the box, even with a doubler. That's a very nice installation, ya' done good!

P.S. -- Don't go throwing around things like "Bernoulli's principle". Before you know it, Gordon will be in here muddying up the water with all his physics. --- waiting.....waiting.....

I almost tried a baffle before moving the oil cooler to see, but the baffles were cracked and I had to take it all apart anyway. Now we’ll never know :lol:

And thanks!!
 
My oil cooler is mounted in the same location on the baffle as yours was, except that I tilted the top back to give the air better access to the lower part of the cooler. The temperature has never exceeded 190* on a hot day. I also used several layers of aluminum sandwiched together carrying the loads to the cylinder head and the crankcase. So far no troubles.
 
My oil cooler is mounted in the same location on the baffle as yours was, except that I tilted the top back to give the air better access to the lower part of the cooler. The temperature has never exceeded 190* on a hot day. I also used several layers of aluminum sandwiched together carrying the loads to the cylinder head and the crankcase. So far no troubles.

I looked into doing this but didn't have enough room around my engine mount to tilt aft. A great suggestion if there's room, though.

I made a doubler on my last baffle repair that was doing ok, but I think the support bar tied into the cylinder head (white in before pictures) was fixing the starboard side of the oil cooler and causing the vibes to increase on the port side. Which is where all my cracking was. I think I could have removed that and added an aluminum L to the corner of the baffles and it would've been fine for cracking, but I never got to test that theory.
 
P.S. -- Don't go throwing around things like "Bernoulli's principle". Before you know it, Gordon will be in here muddying up the water with all his physics. --- waiting.....waiting.....
Fishing's kinda slow today......
 
Now you'll have to close up that bottom cowl like it used to be and see if things remain constant.....
 
Fishing's kinda slow today......
The snappy comeback pond seems to have been drained. I couldn't find anything at all in it - sorry.


Oh wait. Hereya go Perry. The snappy comeback pond seems to be obscured by silt and other inscrutable detritus. There.

Just needed a li'l glass of inspiration.
 
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Congrats. I just installed a 10 row cooler (up from 7 row) to see if that will help my OTs.

Feel free to post in here how it works out. I spent a ton of time and mental energy trying to tackle this one. I'd love to help if I can.
 
I must've really hit bottom. I can't even evoke an insult anymore. At least it wasn't Bartoli's principle.
Well, my friend, maybe my reply was a better insult than I had imagined! Yah, that's it. The bait was unworthy of snappy comeback. Why didn't I think of that earlier?

Sorry for the hijak everyone. It's Perry's fault, though.
 
I’m now having the opposite issue with oil temps, but very happy to be dealing with that! I made a makeshift block to experiment with size requirements. Turns out I was way off. I added a bunch of layers of aluminum tape at my fuel up stop. This size hole got me to 190 degrees. OATs were 40-45. Opening is normally 4”.
ee065fd52d74cb884d691f1158513adb.jpg


I’m going to make something much cleaner that’ll slide in place, with some adjustment available from fully closed to probably 3/4 or so.

Just another follow-up. The new cooler location has been 100% satisfactory. I’m looking forward to summer temps to see how it does!
 
I’m now having the opposite issue with oil temps, but very happy to be dealing with that! I made a makeshift block to experiment with size requirements. Turns out I was way off. I added a bunch of layers of aluminum tape at my fuel up stop. This size hole got me to 190 degrees. OATs were 40-45. Opening is normally 4”.
ee065fd52d74cb884d691f1158513adb.jpg


I’m going to make something much cleaner that’ll slide in place, with some adjustment available from fully closed to probably 3/4 or so.

Just another follow-up. The new cooler location has been 100% satisfactory. I’m looking forward to summer temps to see how it does!

check out the butterfly closer I made for the wildcat cub oil coolers... http://www.supercub.org/forum/showthread.php?49775-Wildcat-Cub/page10
 
Feel free to post in here how it works out. I spent a ton of time and mental energy trying to tackle this one. I'd love to help if I can.
Question Tom. How did you attach that deflector/baffle behind cyl#4?

I replaced my 7 row with a 10 row cooler (Aero Classics). The 7 row was canted aft but the bigger one didnt fit the same due to engine mount interference. Replaced the vernatherm with a spring and plunger. Each change helped 10-15 degrees. Running Aeroshell 100w plus. My vernatherm was not moving as much as the specs say so I'm sure some oil was bypassing all the time.
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I only attached the cooler by the flanges on one side. Is that kosher? Will they crack unless support from the rear flanges as well?
I still wouldn't mind lower temps. I'm seeing 210+F in a long climb. 200-205 cruising at 12K with 60F OAT. It's hard to run too cool up here. I'm going to try Phillips 25-60 oil since Aeroshell is scarce here.
 

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Question Tom. How did you attach that deflector/baffle behind cyl#4?

I replaced my 7 row with a 10 row cooler (Aero Classics). The 7 row was canted aft but the bigger one didnt fit the same due to engine mount interference. Replaced the vernatherm with a spring and plunger. Each change helped 10-15 degrees. Running Aeroshell 100w plus. My vernatherm was not moving as much as the specs say so I'm sure some oil was bypassing all the time.
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I only attached the cooler by the flanges on one side. Is that kosher? Will they crack unless support from the rear flanges as well?
I still wouldn't mind lower temps. I'm seeing 210+F in a long climb. 200-205 cruising at 12K with 60F OAT. It's hard to run too cool up here. I'm going to try Phillips 25-60 oil since Aeroshell is scarce here.

DJ, it’s not attached to anything. More of an interference fit of sorts. Viewed from above it used to be an “L” shape, with the short leg pointing forward towards the prop. I trimmed the short leg to fit the contour of the cylinder the same as my baffle section where the cylinder bore fins change. The long leg is pretty tall and goes all the way to the bottom of the baffle section. Once I got it fit into place, I bent the top part of the long leg forward to allow more air into the SCAT for the oil cooler.

Let me know if that’s not a great description and I’ll draw some pictures. It’s tough to describe.

What were your OTs before the swap?

My theory is this:
-the air above the engine is *essentially* stagnant with little relative flow. The pressure differential between the top and bottom of the engine creates a “suction” that accelerates the air through the fins of the cylinder/oil cooler.
-once the air starts accelerating in a direction, like down through the fins, it would take a stronger pressure differential to accelerate it in a different direction and curve its path through the oil cooler fins.
-when the oil cooler has some space between it and the cylinders, I think it creates a space that the “stagnant” air can spread into. From there it’s either accelerated through the fins or the oil cooler.
-I think that the less space there is between the oil cooler and the fins, the less air will travel through the oil cooler. I think the effect is seen more in installations with more of the oil cooler “covered” by the fins. Since the stagnant air is accelerated, it’s speed is slower at the top of the fins and is more likely to get accelerated through the oil cooler. The further down the engine fins the air gets the faster I think it’s going and the less likely it is to get accelerated through the oil cooler.

Just my thoughts.
 
Thanks Tom. I ran out of Aeroshell and had to switch to Phillips 25-60. Should have been an improvement but instead, I saw an immediate jump of at least 10 F oil temps. Pressure dropped 5-10 psi at idle. Now in the 40s. They tell me it's impossible to get Aeroshell here. Guess I'll be trying a baffle like yours.

Sent from my SAMSUNG-SM-G900A using SuperCub.Org mobile app
 
Replaced the vernatherm with a spring and plunger. Each change helped 10-15 degrees. Running Aeroshell 100w plus. My vernatherm was not moving as much as the specs say so I'm sure some oil was bypassing all the time.

Is (was) your vern a part of the oil filter housing, or...? Simple cap replaced the vernatherm body/cap?

I am tempted to go to the spring and plunger for your exact reasons.
 
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