CHT temps at altitude

[warrenehc]

Hello,

Today I flew for the first time at 16,500.

Normally I fly at 12,500/11,500.

CHT temp on number two was lower then normal. 
16,500

80 ROP

0 Celsius OAT

Is this normal or am I over thinking since #2 normally runs cooler.

[kortopates]

it’s not an approved for primary engine monitor - meaning one of the CHT’s is not using a standard CHT probe, but an adapter or spark plug probe. Is it on cyl 2?
Cyl 2 isn’t the usual spot for this but i’ve seen anything goes after reinstalling after a overhaul. bottom line, given the monitor, need to know what kind of probe is in cyl 2 before trying to properly interpret.


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[M20F]

Would add those CHT’s do not align with that oil temp.  I would check the accuracy of the probes as well. 

[Will.iam]

Even cyl 1 is almost 100 degrees cooler than cyl 3. Is cyl 3 normally that much hotter than the rest in a lycoming 360 or is there a cooling issue there?

[81X]

To me, it seems like your #2 CHT probe is going bad.  180F seems questionably low especially with your EGTs being pretty consistent. 

[carusoam]

Often, we discuss ranges for CHT…

a number was tossed in the other day….

all cylinders are usually within 50°F of each other…

When EGTs are close, and baffling is working well…

 

The pic above shows EGTs being pretty close together… and CHTs not following along at all….

Could be instruments…. Could be baffling…  but, you are asking the right questions…

Got any data from lower altitudes?

Best regards,

-a-

[A64Pilot]

I think the comment on oil temp is key, it’s unlikely for an engine in cruise to have a cyl head temp significantly lower than oil temp.

‘If it’s not a probe problem, I’d do a compression test to just rule that out.

[Ragsf15e]

On 9/4/2022 at 7:37 AM, Will.iam said:

Even cyl 1 is almost 100 degrees cooler than cyl 3. Is cyl 3 normally that much hotter than the rest in a lycoming 360 or is there a cooling issue there?

#3 is commonly the hottest.  The baffling is pretty tight against the back of it and can restrict airflow.  There are several tricks to open up airflow around the back.  #1 is usually coolest.  Mine will have a difference of ~60 degrees or so depending on power setting and oat. 2/4 fall between 1/3. 
 

His #2 temp and oil temp both seem unlikely.