FWIW, we do all our DPTs with te engine hot. So I don't think there's any concerns with removing plugs when hot. Same goes for installing.

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Cool! I'll try it next time I fly.

Thanks!

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.

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

I don't have much to offer in the way of advice but I'm sure impressed with your stick-with-it on this issue. You're learning valuable things and getting intimate with your toy. That impresses me! Keep after it, sure a nice looking bird!

Jeredp wrote:I don't have much to offer in the way of advice but I'm sure impressed with your stick-with-it on this issue. You're learning valuable things and getting intimate with your toy. That impresses me! Keep after it, sure a nice looking bird!

Thanks Jered!

I'm trying my best to publish everything I can about this because I've read of others with the same problem and never heard what the root cause was. The fixes I've heard of are usually "I just added a second oil cooler" or things like that. The system SHOULD work like all the others, granted it's in a unique installation. I'm trying to capture what I've done for the next guy.

Well, I spent some time aloft this weekend (6.3 hrs!) and most of it was in class G, thinking about stuff and things.

I was thinking about how on my last flight, in a descent, the oil temps increased. Throttle remained the same, I just pitched nose down and accepted the higher airspeed. No throttle adjustment. It just didn't make sense.

Anyways, at some point over central AL I reached up and flipped my wig-wags and strobes off and saw about an 8 degree OT drop nearly immediately. Pulling the alternator field CB got another 5 or so. Hmm.

I knew there was a problem with the old temp sender and when it got replaced the erratic readings went away. And then I *thought* I'd verified the indicating system with a can of hot oil. What I didn't think about was that the engine, alternator and the electrical consumers were off.

So now that I've got cord showing in one of my tires, I'm bringing the airplane down to do some maintenance that I've been putting off for a little while. One of those things is re-running some grounds. Hotrod 180, I'll also be replacing those exhaust tips you love, haha. I'll also be installing my Pmag, finally. I'll report back when she's flying again.

Pop quiz: how many hours would you guess this oil has on it?

CamTom12 wrote:Pop quiz: how many hours would you guess this oil has on it?

Can you give us a hint...Total Time Since Overhaul/Top?

8GCBC wrote:

CamTom12 wrote:Pop quiz: how many hours would you guess this oil has on it?

Can you give us a hint...Total Time Since Overhaul/Top?

270 SMOH

6.3 hrs. It's doing a lot of ashless dispersing.

CamTom12 wrote:

8GCBC wrote:

CamTom12 wrote:Pop quiz: how many hours would you guess this oil has on it?

Can you give us a hint...Total Time Since Overhaul/Top?

270 SMOH

Thanks...

OK. One more hint:

What's the differential compression: ??/80 ??/80 ??/80 ??/80

This is fun!

73, 75, 74, 77

Survey says....

50 hours on the TACH?

Z was a lot closer, there's just less than 17 hrs on that oil. That's a hot sample, too.

I thought it coated the side of the glass well and although it looks a little dark to me I think it's doing ok. Purely an eyeball inspection though. I'm going to change it early this time for another blackstone labs sample. Shooting for about 30 hours on the oil for the next sample. The last sample had 50 hrs on it.

CamTom12 wrote: Did some maintenance today, pulled and cleaned all the plugs and reinstalled them in the same cylinders, but swapped bottoms and tops.....

FWIW here's a diagram of how Champion suggests rotating the plugs.
Something to do with polarity of the spark, and extended electrode life.

hotrod180 wrote:

CamTom12 wrote: Did some maintenance today, pulled and cleaned all the plugs and reinstalled them in the same cylinders, but swapped bottoms and tops.....

FWIW here's a diagram of how Champion suggests rotating the plugs.
Something to do with polarity of the spark, and extended electrode life.

The mags are spinning opposite each other on the gear train so the spark on one will propogate spark plug tip out and the other will go outside in. Wears the center electrode differently. So yeah, swap top to bottom and left mag to right mag. Or bottom to top and right to left. You get it.

CamTom12 wrote:Z was a lot closer, there's just less than 17 hrs on that oil. That's a hot sample, too.

I thought it coated the side of the glass well and although it looks a little dark to me I think it's doing ok. Purely an eyeball inspection though. I'm going to change it early this time for another blackstone labs sample. Shooting for about 30 hours on the oil for the next sample. The last sample had 50 hrs on it.

Correction: it has 14.6 hours on it. I just re-checked my math.

StampCreek wrote:

hotrod180 wrote:

CamTom12 wrote: Did some maintenance today, pulled and cleaned all the plugs and reinstalled them in the same cylinders, but swapped bottoms and tops.....

FWIW here's a diagram of how Champion suggests rotating the plugs.
Something to do with polarity of the spark, and extended electrode life.

The mags are spinning opposite each other on the gear train so the spark on one will propogate spark plug tip out and the other will go outside in. Wears the center electrode differently. So yeah, swap top to bottom and left mag to right mag. Or bottom to top and right to left. You get it.

Ah, makes sense. I'll do that next time. Thanks guys!