Engine Cooling Fixes

[Gilbert Pierce]

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.!

That was convient wasn't it?��

[Gilbert Pierce]

I see the same CHT's this time of year. When the OAT's come up to normal mid-south temps your CHT's will respond accordingly I believe.

[CamTom12]

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!

[Steve Pierce]

Nice cool OATs, we got into the mid 80s this weekend and expecting 90 plus today.

[CamTom12]

77 today, 78 tomorrow, 62 on Wed

[Gilbert Pierce]

Delta P front to rear of oil cooler?

[CamTom12]

Sort of. High pressure probe is on top of the engine and the low pressure probe is behind the oil cooler.


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[CamTom12]

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

#4 top

#1 bottom

#3 bottom


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.


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.




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.


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.

[CamTom12]

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.


Here's the oil after 4.9 hours of flying (cold reading, thicker oil):





Here's the oil after 8.3 hours of flying (hot reading, thinner oil):





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.

[CamTom12]

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.