Winter Cylinder Head Temps

[M20F-1968]

I took the plane out 2 days ago.  OAT at 6500 ft., 70% power, about 2300 RPM and 23 MP, cowl flaps closed, cylinder 1-3 were in the 315-325 range, and #4 was 298.  

What is the lowest acceptable temp and why?  I know that carbon buildup is more at lower temps.  Also, when leaning to 100 ROP, my TIT runs up to about 5300 degrees.  I think the redline is about 5800 and the yellow arc starts at 5000.  Does this seem to be set correctly.  I have an aftermarket turbonormalizer on the F (now mostly a J) so the turbo TIT is set without factory guidance.  What ranges of TIT has Mooney used on the 231 over the years?

John Breda

[N201MKTurbo]

The #2 on my engine, before I rebuilt it, would always read low. Around 275. I was concerned about it, but it never seemed to cause any issues.

[M20F]

Fairly certain your TIT is not 5300 degrees. 

[A64Pilot]

IF power is high, the. low cyl head temp isn’t nearly as big an issue, remember combustion temps, exh valve etc are still very close to the same temps as always.

Low Cyl temp along with low power settings is however more of a problem with carbon build ups etc and lead, biggest issue in my opinion is getting sticking exh valves.

I can’t advise anyone to put MMO in their oil, but I’ve seen a few R-1340’s that will stick valves without it, and not stick valves when it’s used.

People in Ak who fly bush regularly block off some of the cooling air at the inlet to keep normal operating temps, many older aircraft also had “winteraziation” kits that consisted of sheet metal pieces that partially blocked off cooling ducts, my C-140’s kit even had an asbestos blanket that wrapped around the oil tank.

Now if no one else in the Mooney world is doing this up there where you live, then it’s not likely you should as you can overdo it and overheat a motor if you’re not careful.

I am not a turbo pilot, but I believe often the TIT is what determines position of the red knob and not X EGT like we use on N/A motors, but actual turbo drivers will chime in I’m sure. I’d try to find one with a similar system as you have as a K model may act differently, and it seems even with them they differ based on mods done.

[Shadrach]

If it’s not fouling plugs than it’s fine regarding CHTs.  

Sustained Oil temps below 180 are not desirable. I’ve seen water dripping out of the breather after flights where the oil did not come up to temp.

[Red Leader]

I thought the higher temperatures were better for lead scavenging? I have heard that if the temps are lower, you are more likely to have lead deposits in the exhaust (though that may be just for EGT, so correct me if I am wrong). As far as TIT goes, I fly a K and the redline on my bird is 1650. I understand temps up to 1750 are allowable for no more than 30 seconds but that is for an engine designed from the factory to work with the turbo. I try not to run it much above 1600 and ideally closer to 1550. Yes, your red knob will dramatically affect TIT. A recent MS'er who just purchased his K, made the comment that he feels he is just chasing temperatures - he is correct, that is what we do but getting to a perfect balance can be done (but tricky). Since yours is turbo-normalized, I cannot say with any degree of certainty if those numbers will apply to you. Is your POH updated to cover the operational specifics of the turbo-normalization?

[Shadrach]

18 hours ago, Red Leader said:

I thought the higher temperatures were better for lead scavenging? I have heard that if the temps are lower, you are more likely to have lead deposits in the exhaust (though that may be just for EGT, so correct me if I am wrong). As far as TIT goes, I fly a K and the redline on my bird is 1650. I understand temps up to 1750 are allowable for no more than 30 seconds but that is for an engine designed from the factory to work with the turbo. I try not to run it much above 1600 and ideally closer to 1550. Yes, your red knob will dramatically affect TIT. A recent MS'er who just purchased his K, made the comment that he feels he is just chasing temperatures - he is correct, that is what we do but getting to a perfect balance can be done (but tricky). Since yours is turbo-normalized, I cannot say with any degree of certainty if those numbers will apply to you. Is your POH updated to cover the operational specifics of the turbo-normalization?

Lead scavenging is more about plug temp than CHT.  Plugs need to be above about 800° For the ethylene dibromide to do its job. As I said, if it’s not fouling plugs, than the temp is sufficient. My #1 and #4 CHTs run in the 280-300 range and even cooler when OATs are in the teens. John is running a Turbo Normalizer with stock compression ratios. His TIT will run considerably cooler than your lower compression K model.

[M20F-1968]

On 11/26/2022 at 11:29 AM, M20F said:

Fairly certain your TIT is not 5300 degrees. 

Sorry I had 5 in my mind - that should read 1530

John Breda

[Will.iam]

Just got my airplane back from annual today and high temp for the day was 50 degrees F. I flew back home at 22” and close to peak tit. Thought the oil had come up to temp as cht had gone up to 360 in the climb but after level off and bringing power back they settled on 325 to 290 but apparently only a 30 min flight wasn’t enough as i had water dripping out of the breather tube. Also noticed it took my dehumidifier and extra hour to get most of the moisture out of the engine where normally 30 mins will purge it.