What is a colder cylinder telling me

[AggieMike88]

Today, I flew 55WB (1975 C182P) to the Texas Panhandle to deliver some PnP dogs and pick up a monkey. Frogs97 accompanied me.

One hour into flight, he asked about the CHT monitor on the panel and I told him how he could switch through each cylinder to see the reading and how the system shows me which is hottest at that moment.

He pointed out that the #6 cylinder (as shown on the instrument) was being shown 80-90° cooler than the rest. The others were around 350°-360° at 8000 feet, cowl flaps closed, 21.5 MP WOT, 2300 RPM. This condition continued through the flight. No other roughness or problems were detected.

We made sure to observe this on the return flight. Similar conditions, 7000 feet, and we saw about a 70° degree cooler differential.

What should I be learning from this?

I don't remember the brand/model of the gauge, but if you check out the panel photo, it's the instrument in the upper right above the circuit breakers.

 

[Jay Honeck]

What was the EGT spread like?

Here's why I ask: My plane is currently a 3-cylinder, as I await delivery of my new Lycoming cylinder. We had been watching #4 after it had shown lower (68/80) than normal compression at annual last February.

Last week on a routine flight I received an EFIS alarm due to the engine monitor detecting a "too-far-apart" EGT range of 100+ degrees. Sure enough, it was #4, so I did a compression check after landing and found it to be 58/80.

We pulled it.

If #6 is running that much cooler than the rest, I would do a compression check on it just to allay your worries. Heck, it might just be a bad probe.

 

[AggieMike88]

We're not equipped to see EGT on all the cylinders. I just have the single gauge. And I didn't make note of what it said specifically.

 

[timwinters]

#6 is your front cylinder on the pilot's side. It will run the coolest.

#5 is your front cylinder on the co-pilot's side. It won't run as cool because the oil cooler is in front of it.

Likely nothing wrong.

 

[AggieMike88]

How is your oil consumption?

Low... Because were equipped with a screen, we're changing oil every 25 hours. Per the useage log, I'm seeing none or 1 quart added between changes.

 

[N801BH]

Low... Because were equipped with a screen, we're changing oil every 25 hours. Per the useage log, I'm seeing none or 1 quart added between changes.

Fly it.......

Sounds like a CHT sending unit has lost it's value...

 

[Henning]

#6 is your front cylinder on the pilot's side. It will run the coolest.

#5 is your front cylinder on the co-pilot's side. It won't run as cool because the oil cooler is in front of it.

Likely nothing wrong.

Yeah, that, #6 is the only one in clean cool air.

 

[AggieMike88]

#6 is your front cylinder on the pilot's side. It will run the coolest.

#5 is your front cylinder on the co-pilot's side. It won't run as cool because the oil cooler is in front of it.

Likely nothing wrong.

Flew today between KDTO and T35 with 6PC on board. Our observation today was more in a normal range with the #1 being the hottest around 355° and the #1 being about 298°. 5000ft MSL, 23/2300, cowl flaps closed, ambient temp about 55°F

I think you all are correct that the noticeable difference is because it's the only cylinder with direct air flow.

And perhaps yesterday's larger differential was because we were higher and the OAT was much cooler.

 

[Checkout_my_Six]

#6 on mine was the hottest....

your #6 could be the leanest cylinder....or the richest....depending on how you were running it.

 

[timwinters]

#6 on mine was the hottest....

On your what?

And with a Conti or Lyco?

 

[Ted]

It most likely means it's running the coldest. Don't worry about it.

 

[GLMS_NC]

You can swap the egt probe with another cyl to rule out a bad probe.

 

[Checkout_my_Six]

On your what?

And with a Conti or Lyco?

Conti.....

 

[flyingron]

It's also important to note if you have a CHANGE from previous observations. CHT probes aren't always an absolute number. My #3 cylinder reads way different than the others on my JPI because the probe is different on that cylinder (The main probe hole has the "official round cht guage" probe in it).

Note while the answer above is true for the 182's continental, just for others watching Lycoming engines have the reverse numbering (The cylinders are numbered from the prop end on Lycomings). Most lycomings also have the #1 cylinder on the right side, though there are a few oddballs that have the #1 on the left.