One cylinder hotter than the others, should I worry?

[AndreiC]

Now that the temperatures in my part of the country are getting higher (high 80s, low 90s -- I know, we are lucky this way in Wisconsin), I started to pay attention to CHTs. Yesterday on a regular flight at 6500ft my CHTs were 335, 353, 318, 319 for #1-#4.  Obviously #2 is much higher than the others, but still well below 380. My question is if I should worry, or if I should operate the engine in any way different from what I am doing. Maybe it should be mentioned that cylinders 2 and 4 have just had their intakes pulled off for an unrelated reason, filed and reinstalled with new gaskets; #2 was always the hottest running cylinder, even before this gasket replacement.

Stats for the flight were WOT, 23.5" MP at 6500 FT, OAT at altitude 70F, 2500 RPM, 9.4 GPH leaned to peak. I think that is 71% power for the IO-360 I have. My plane has the LASAR guppy mouth closure. Cowl flaps were closed. 

Any thoughts on this? Thanks!

[GeeBee]

I would not worry. As I remember, the Sky Ranch manual said up to 20% of the highest in differential is acceptable.

[Shadrach]

1 hour ago, AndreiC said:

Now that the temperatures in my part of the country are getting higher (high 80s, low 90s -- I know, we are lucky this way in Wisconsin), I started to pay attention to CHTs. Yesterday on a regular flight at 6500ft my CHTs were 335, 353, 318, 319 for #1-#4.  Obviously #2 is much higher than the others, but still well below 380. My question is if I should worry, or if I should operate the engine in any way different from what I am doing. Maybe it should be mentioned that cylinders 2 and 4 have just had their intakes pulled off for an unrelated reason, filed and reinstalled with new gaskets; #2 was always the hottest running cylinder, even before this gasket replacement.

Stats for the flight were WOT, 23.5" MP at 6500 FT, OAT at altitude 70F, 2500 RPM, 9.4 GPH leaned to peak. I think that is 71% power for the IO-360 I have. My plane has the LASAR guppy mouth closure. Cowl flaps were closed. 

Any thoughts on this? Thanks!

Are you running bayonet probes on each cylinder?

[Ragsf15e]

For a guppy mouthed vintage Mooney, those temps are actually pretty even and not actually that warm.

[Fly Boomer]

1 hour ago, AndreiC said:

Obviously #2 is much higher than the others, but still well below 380.

Unless he has changed his mind, Mike Busch says 380 for Continental and 400 for Lycoming.  It's on PDF page 6 of this document:

Temperature, Temperature, Temperature.pdf

 

[AndreiC]

1 hour ago, Shadrach said:

Are you running bayonet probes on each cylinder?

Yes, I think so. I mean, the ones I have are the ones that thread into a specially designed socket in the cylinder, and not something on the spark plug.

[AndreiC]

1 hour ago, Ragsf15e said:

For a guppy mouthed vintage Mooney, those temps are actually pretty even and not actually that warm.

Yes, but as I said the opening has been closed up using the LASAR mod.

[AndreiC]

BTW, my oil temp was 202F. My guess is that this is a good oil temp to be operating at, but just checking. 

[PT20J]

6 minutes ago, AndreiC said:

BTW, my oil temp was 202F. My guess is that this is a good oil temp to be operating at, but just checking. 

Should be fine. It depends on where the probe is.

If you want to check the instrumentation, two easy checks are swapping probes to see if temperature follows probe or stays with the cylinder and heating each probe with a heat gun to check that they are connected to the proper channel.

[Ragsf15e]

36 minutes ago, AndreiC said:

Yes, but as I said the opening has been closed up using the LASAR mod.

Yes, mine too, same mod.  That being said, the remaining opening isnt optimized like a J model which keeps temps a bit closer.  Yours are actually a little more even than mine.  My 3 is hotter due to the known issue with the fins (or lack) against the back baffles but it depends on which cylinder is leanest or richest.

[MikeOH]

@AndreiC

Your numbers look a little better than mine at 70%.  My #2 has always been hottest, as well.  Spread isn't any worse than mine either.  I normally run closer to 65% with numbers a little lower, but not by much.  My observations are based on nearly 7 years of ownership of my F.

[Shadrach]

#3 is typically the hottest in this application under most scenarios but close to #2. That reading is amplified by using a spark plug ring thermocouple and reduced by using a piggy back on a bayonet.

[1980Mooney]

18 hours ago, AndreiC said:

Now that the temperatures in my part of the country are getting higher (high 80s, low 90s -- I know, we are lucky this way in Wisconsin), I started to pay attention to CHTs. Yesterday on a regular flight at 6500ft my CHTs were 335, 353, 318, 319 for #1-#4.  Obviously #2 is much higher than the others, but still well below 380. My question is if I should worry, or if I should operate the engine in any way different from what I am doing. Maybe it should be mentioned that cylinders 2 and 4 have just had their intakes pulled off for an unrelated reason, filed and reinstalled with new gaskets; #2 was always the hottest running cylinder, even before this gasket replacement.

Stats for the flight were WOT, 23.5" MP at 6500 FT, OAT at altitude 70F, 2500 RPM, 9.4 GPH leaned to peak. I think that is 71% power for the IO-360 I have. My plane has the LASAR guppy mouth closure. Cowl flaps were closed. 

Any thoughts on this? Thanks!

You never mentioned exhaust temperatures.  Do you have an engine monitor that measures exhaust temperatures on each cylinder?  If so is #2 in line with the others?

[AndreiC]

18 minutes ago, 1980Mooney said:

You never mentioned exhaust temperatures.  Do you have an engine monitor that measures exhaust temperatures on each cylinder?  If so is #2 in line with the others?

Yes, the EGT's on 1, 2, and 3 are all within maybe 30 degrees of each other. #4 has a lower EGT for some reason (while leaned to peak), maybe 50-60 degrees total difference between highest and lowest.

[TheAv8r]

On my M20E the #2 cylinder always runs the hottest, it has done so on both my old engine and my freshly overhauled one. My A&P and I speculate it's because of p-factor, the #1 cylinder runs the coolest and receives the most airflow from the prop, which supports that theory. 

[Ragsf15e]

20 hours ago, AndreiC said:

Yes, but as I said the opening has been closed up using the LASAR mod.

I took pictures of my engine temps running ROP and LOP today at 7500’, warm OAT (at least for Washington).  I have the same Lasar cowl closure.  I’m thinking your temps are pretty normal.

(I’m in “normalize”, so the bars look even, but look at the actual values)

100 ROP

 

~10 LOP

Edited July 16 by Ragsf15e

[MikeOH]

@Ragsf15e

Please tell me you aren't counting on that cardboard CO detector, and have something better elsewhere in the cabin.

Numbers wise, those CHTs look very close to what I see at 70% and 65%, respectively.

[Ragsf15e]

1 hour ago, MikeOH said:

@Ragsf15e

Please tell me you aren't counting on that cardboard CO detector, and have something better elsewhere in the cabin.

Numbers wise, those CHTs look very close to what I see at 70% and 65%, respectively.

Ha! No, I have a sensorcon mounted at eye level on the canopy bow.  I should take that one down, it’s old.

[M20F]

I would only add that it would be useful to post +/- ISA versus ambient.  We go through these posts every summer when here in Atlanta as example it was +15C ISA today, what would one expect?  I flew back from MN yesterday at 9000 and got better cooling at 3500 on leg 2.  It’s hot and humid. 
 
To @AndreiC if #2 is substantially different then usual (see similar post by @Shadrach) then reason for concern.  If the spread is the same and they are all hotter than normal, welcome to summer. 

[Ragsf15e]

42 minutes ago, M20F said:

I would only add that it would be useful to post +/- ISA versus ambient.  We go through these posts every summer when here in Atlanta as example it was +15C ISA today, what would one expect?  I flew back from MN yesterday at 9000 and got better cooling at 3500 on leg 2.  It’s hot and humid. 
 
To @AndreiC if #2 is substantially different then usual (see similar post by @Shadrach) then reason for concern.  If the spread is the same and they are all hotter than normal, welcome to summer. 

Yeah, that’s fair (isa temp dev).  I included the temp but was too lazy to look up isa.  It’s 0c at 7500’, so I was isa +16c.  The other thing that can be counterintuitive is that you can get higher cylinder temps at higher altitudes even in an NA engine.  The air is much thinner as you go higher, so even though it might be cooler and you’re making less power, you can still end up with warmer chts just because you can’t cool them as well with the less dense air.  I find that effect pretty noticeable by about 7000’ and above with the mooney, especially when it’s also hot.