PROPER CHT'S (CYLINDER HEAD TEMPS)

[BRBENNETT]

Mooney M20F, Lycoming IO360-A1A

I thought would put this out there for some advice & feedback.  Recently I had my mechanic examine my engine and he mentioned pooling of oil and possible cylinder glazing.  Cylinder glazing is a condition that occurs where oil film left on the bore "glazes" to a hard coating and can prevent optimal sealing of ring to bore.  The oil here is the result of cylinder head temperatures, CHT'S, not getting hot enough to burn this oil film and. thus prevent the glazing.  Optimally, he says, the CHT'S should run about 360-380 F. 

My engine is seeing a range of 300-320 deg F with an OAT of around 34 F.  This is with cowl flaps completely closed all the way, they are closed and flush with the rest of the cowling.  All cylinders are running about within 10-15 degrees of each other & measured by JPI930 engine monitor.

Of course, my goal is to get these temps into the suggested range.

Just wondering if anyone is running into the same issue?  what temps do you typically see?  Has anyone found a way for the cowl flaps to create more flow restriction?  has anyone done anything with engine baffling as to affect the cooling of the engine?

Thanks for any feedback.

04/19/2018 -- ADDITIONAL INFORMATION:

Thanks for everyone's feedback!  what a great resource!

I thought I would share what led to the inspection of the cylinders and a give a clarification of the above statements.

On a couple of occasions, a ramp guy took notice of a puff of white smoke when taxiing up the ramp.  Curiously, I mounted a go pro camera and focused it on the exhaust to try and observe it myself and of course, it never showed up.  Recently, I pulled the cowl to check a few items and noticed oil coming out between the exhaust manifold and tube flange at cylinder#4.  I immediately sent it in for service and it ended up being a bad valve guide.  With all that said, cylinder#4 has undergone a rebuild and will require break-in, hence, the recommended higher CHT's.  After clarification and reading all the great comments, this is why he mentioned the glazing and the importance of running  higher CHT's.   My fault on the interpretation.  Fortunately, I do not have any cylinder glazing as all cylinders. were checked at this time.

For those that asked, oil consumption has been in the normal range.  I have 2 years of history (about 400hrs worth) and it ranges from 0.10 to 0.15 qt/hr.  This looks to be well below even what Lycoming says is normal.  I found this formula in their manual Normal Oil Consumption (Qt/hr) =(0.006 * BHP * 4) / 7.4.  At a BHP of 0.59, this equates to 0.19 qt / hr.  Compressions are all good ranging from 77 to 80.  

One question I do have for all of you, When do you typically add oil?  Do you wait til it gets down below the 6qt mark, or, do you add it when it is hovering just above around the 6qt mark?  I have been doing to latter.  I have heard that these engines typically find their happy spot and then do not vary much.  I may be adding too early as it may stabilize at 6qt.  Any thoughts here appreciated.

 

 

Edited April 19, 2018 by BRBENNETT

[Cyril Gibb]

Your mechanic doesn't know his a** from a hole in the ground.  Glazing is usually a result of poor break-in.  Your cylinder temps are perfect.

edit: was that worded too strongly?

[Marauder]

Mooney M20F, Lycoming IO360-A1A

I thought would put this out there for some advice & feedback.  Recently I had my mechanic examine my engine and he mentioned pooling of oil and possible cylinder glazing.  Cylinder glazing is a condition that occurs where oil film left on the bore "glazes" to a hard coating and can prevent optimal sealing of ring to bore.  The oil here is the result of cylinder head temperatures, CHT'S, not getting hot enough to burn this oil film and. thus prevent the glazing.  Optimally, he says, the CHT'S should run about 360-380 F. 

My engine is seeing a range of 300-320 deg F with an OAT of around 34 F.  This is with cowl flaps completely closed all the way, they are closed and flush with the rest of the cowling.  All cylinders are running about within 10-15 degrees of each other & measured by JPI930 engine monitor.

Of course, my goal is to get these temps into the suggested range.

Just wondering if anyone is running into the same issue?  what temps do you typically see?  Has anyone found a way for the cowl flaps to create more flow restriction?  has anyone done anything with engine baffling as to affect the cooling of the engine?

Thanks for any feedback.

 

I’ve been flying my F for 27 years with temps in that range (and even lower in the winter) and the glaze monster (pun) hasn’t gotten me.

 

 

I don’t buy that low temps are your issue. And I don’t buy you have a legitimate issue. Since you have a 930, sign up for SavvyAnalysis and let them (Paul) look over your data. You temps are in the ballpark with a number of F models.

 

 

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[Marauder]

Here is another datapoint. My analysis of CHTs when compared to other IO-360s.

As Cyril says, you may want to look for someone a little more knowledgeable. 

[jaylw314]

46 minutes ago, Cyril Gibb said:

Your mechanic doesn't know his a** from a hole in the ground.  Glazing is usually a result of poor break-in.  Your cylinder temps are perfect.

edit: was that worded too strongly?

+1.  AFAIK, glazing only occurs if oil is not wiped off the cylinder walls by the rings, and that is why you break them in at high power.  once the rings are broken in, they will wipe off the oil with each stroke.

I should also point out that your CHT's measure the cylinder head temp, NOT the temp during combustion.  As such, flying in cold air will reduce your CHT even if the internal cylinder temp is actually the same.  I will generally get only 310 degF during the winter and 360 degF during the summer at the same power settings.

[Nomad Pilot]

Cylinder temps are not perfect!!! Your mechanic is correct on CHT range.


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[MyNameIsNobody]

49 minutes ago, Nomad Pilot said:

Cylinder temps are not perfect!!! Your mechanic is correct on CHT range.


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NOPE.

[kortopates]

CHTs in the low 300F’s are envy of many. You have nothing to be concerned with, but your obviously running low power cruise. But if you have glazed cyl it suggest it was broken in at too low a power too. But how is your oil consumption ?


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[carusoam]

BRB,

Trying to help you a bit... a summary of what has been covered above... 

1) Your first paragraph is not based in reality... did you miss something the mechanic said?

2) If you transcribed exactly what he said... you have since been approved to... Go ahead and start the search for the new mechanic...

3) Glazing of the cylinder walls occurs when the break-in procedure doesn’t get followed properly... I think your mechanic may have described the diamond making processes of compressing carbon based material under extreme temperatures and pressures... your CHTs didn’t get hot enough for that...

4) if your cylinders have been broken in properly, you get the proper oil useage... 1qt every 10 hrs or so...

5) 380°F is not an optimum CHT.  It is a temperature that provides a level of protection against early cylinder wear.... great for getting to TBO on the original cylinders...

6) If you are cruising around with CHTs in the 320°F range and oil only being added every 10 hours or so... angels are singing in the background when you look at your aviation budget...

7) why would somebody say you should raise your CHT?

8) It is possible in the depth of winter when some CHTs fall out the bottom of the range... the lead chemistry for converting the LL doesn’t get activated....  search around MS it gets mentioned in the really cold days...

9) Does this sound familiar? Or is this all new to you? Your POH has the real limitations in it...  the 380° Recomendation comes from outside cylinder metallurgy experts.  Probably won’t find that in the POH...

10) MS is a great place to get Mooney educated...  

PP thoughts only, not a mechanic...

Best regards,

-a-

Then comes the after thought...

On the other hand...

1) Your break-in didn’t go as well as you hoped...

2) The cylinder walls have evidence of being glazed...

3) Your oil usage hasn’t stabilized anywhere near one qt per ten hours...

4) you brought this to the attention of your trusted mechanic.

5) he explained that he photographed the walls of the cylinders with a tiny dental camera, shared the pics with you via email, and explained what you need to do to resurface your cylinders, and how to re-run the break in procedure...

6) Break in procedures are that important.  It helps to bring somebody along to be SIC while you are PIC for the first couple of hours...  the main part of the break-in can be done in the first 1-10 hours... an engine monitor will tell you when the procedure completes itself...

7) re-surfacing cylinders requires taking them to a cylinder shop to get re-honed... put that nice waffle cross hatch pattern back onto the surface where it belongs...

8) Break-in is typically a high MP operation, done down low, alternating RPM through a range from max to less than max, changing every 15minutes or so.... at full rich and as much cooling you can get....

More PP ideas only.  Did I miss anything?

I hope you found this helpful. Writing about it was helpful for me. 

Best regards,

-a-

 

 

[PTK]

12 hours ago, BRBENNETT said:

... Optimally, he says, the CHT'S should run about 360-380 F...

That's sounds slightly high to be considered "optimal." I normally see lower 300's and have set my EDM to alarm at 390° F. 

Do you keep track of oil consumption?

[Nomad Pilot]

Don’t drink the Mike Bush Kool-Aid!


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[MyNameIsNobody]

1 hour ago, Nomad Pilot said:

Don’t drink the Mike Bush Kool-Aid!


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Troll.

[PTK]

1 hour ago, Nomad Pilot said:

Don’t drink the Mike Bush Kool-Aid!

What’s the Mike Bush Kool-Aid you’re referring to?

[Bob_Belville]

For one thing it's Busch. 

If "drinking his Kool-Aid" refers to using Savvy Aviation expertise and being grateful for @kortopatescontributions to this space then there are a great many Kool-Aid drinkers here, including me. 

[Sabremech]

Mike Busch has some good information for owners/pilots. Being a professional A&P, I don’t agree with him on some things though. That may be why there are differing opinions. Mike is after all trying to make money.

[Bob_Belville]

17 minutes ago, Sabremech said:

Mike Busch has some good information for owners/pilots. Being a professional A&P, I don’t agree with him on some things though. That may be why there are differing opinions. Mike is after all trying to make money.

Ain't we all? Well, not me, I'm busy spending my children's inheritance.

[kortopates]

The only time we have a concern for running too cool is if you are not fully scavenging the lead. Avgas contains a lead scavenging agent" called ethylene dibromide. However the agent needs sufficient combustion temps (not necessarily CHT) to do its job. If combustion is too cool, it results in lead fouling of the plugs. Its true that the scavenging is most effective in the 350-400F range but so what, we hardly operate our engines to maximize lead scavenging. Most of us prefer to operate for maximum cylinder longevity which likes cooler CHTs. Although from a CHT perspective, lead deposits have shown to form with CHTs below 300F,  typically we find this is only a concern with very low power ROP cruise where see both very low EGTs and CHT  (CHTs of 250F and lower). But leaning to peak EGTs when operating at low power does much better and exposure to lead fouling is much less likely. Hopefully all this will be mute soon when we can run lead free avgas.

This is just like the OWT that oversquare is bad for your engine!

The bottom like on Mike is that all of his work is dedicated to educating the pilot community and has been for years. Its been a few years since he started Savvy to work with clients directly for fee, but his business model is all about saving clients money by educating owners on the difference between discretionary maintenance and required maintenance, saying "no" to scheduled maintenance that is neither required nor proven to be helpful - like cleaning injectors on annual schedule and giving the owner control back on their annual invoices by separating the inspection from maintenance and getting estimates for discrepancies before the work is started. He's also all about data driven maintenance rather then premature wrench turning and throwing parts at it. Of course he does not advocate all maintenance be done on condition and is a very vocal on the need to comply with timed Magneto IRAN inspection too. 

If that's cool aide, its the most sensible, logical and scientific reasoning I've been exposed too in the aviation world to date. All of us at Savvy are proud to be associated with him and all he has done for GA.

Edited April 19, 2018 by kortopates

[kmyfm20s]

10 hours ago, Nomad Pilot said:

Don’t drink the Mike Bush Kool-Aid!


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You have mentioned this in a few of your post so pour us a glass of your Kool-aid! I’m always up for hearing another educated point of view. Let the forum discuss it!

[Guest]

Strange that there is no company called “Nomad Pilot Analysis Service”.  When it goes public Savvy should be worried.

Clarence

[Nomad Pilot]

Pouring the Kool-Aid... The original post was an question of low CHT and oil glazing on the cylinder walls. So the first thing I looked at was oil temp (170F). That’s at least ten degrees lower than it should be. My concern was that the he was managing his engine in “no mans land” or specifically below BSFC. This could cause both cylinder glazing and low CHT readings. Running an engine on the back side of lean of peak is a dangerous place to be.

Mike Bush (Savvy) has some very educational webinars on EAA on lean of peak. Bill Ross also has written an excellent pamphlet on engine management (http://superiorairparts.com/files/1715/0273/3473/EM101.pdf) engine management 101. The problem I believe has stemmed from the thought that if 380 CHT is good, 370 is better and 300 is amazing... That’s not so! If your running on the backside of BSFC, your doing harm to the engine.

CHT below 400 is what the manufacturers suggest, but look first at oil temp when you have low CHT.

Side note: Just because I have a different point of view on the subject does not make me a “troll”. We’re all here because we can for our Mooney’s and I’ve learned much from other owners experience with these classic machines. 30+ yrs A&P and I’ve peered though a Boro a time or two.


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[gsxrpilot]

Sorry but it appears your mixing up some of the ingredients in your kool-aid. The 170 degree oil temp is from @Marauder not the OP who's complaining of cylinder glazing. In that post @Marauder says he's been running his airplane this way for 27 years without any ill effect and doesn't have any of this "glazing" either.

I've also read the Bill Ross pamphlet and frankly lost count of how many times he says to follow the manufacturers recommendations. It seems to be on every page. As a "Pro" subscriber to SavvyAnalysis and a graduate of the Deakin/Braly/Atkinson APS class, I'll go with data instead. I'm pretty sure my turbo engine at over 1300 hours on all original cylinders is better for it. 

BTW looking at the SavvyAnalysis of today's flight, my Oil Temp was between 150 and 165 and the CHT's between 290 and 350 the whole flight.

Just my $0.02 

[kmyfm20s]

10 hours ago, Nomad Pilot said:

Pouring the Kool-Aid... The original post was an question of low CHT and oil glazing on the cylinder walls. So the first thing I looked at was oil temp (170F). That’s at least ten degrees lower than it should be. My concern was that the he was managing his engine in “no mans land” or specifically below BSFC. This could cause both cylinder glazing and low CHT readings. Running an engine on the back side of lean of peak is a dangerous place to be.

Mike Bush (Savvy) has some very educational webinars on EAA on lean of peak. Bill Ross also has written an excellent pamphlet on engine management (http://superiorairparts.com/files/1715/0273/3473/EM101.pdf) engine management 101. The problem I believe has stemmed from the thought that if 380 CHT is good, 370 is better and 300 is amazing... That’s not so! If your running on the backside of BSFC, your doing harm to the engine.

CHT below 400 is what the manufacturers suggest, but look first at oil temp when you have low CHT.

Side note: Just because I have a different point of view on the subject does not make me a “troll”. We’re all here because we can for our Mooney’s and I’ve learned much from other owners experience with these classic machines. 30+ yrs A&P and I’ve peered though a Boro a time or two.


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 But Bill Ross only mention low oil temperature in the context that anything less than 180 degrees doesn’t boil of the water and Leeds to engine products causing corrosion. I don’t see how this pertains to the op concern about glazing of cylinders?

cylinder glazing occurs from hot cylinder not cold cylinders with residual oil left oil the walls causing a varnish. Similar to seasoning a cast iron skillet.

[ArtVandelay]

FWIW, im about to run in a new engine on AL, there is a lycoming service bulletin that tells you EXACTLY what to do (not with to hand so ill quote from memory).

1. run engine for one (the first) hour at 75% power continuously, ensure that all turns are gentle and smooth and there is no variation in altitude as this will affect the mo setting and reduce the power.
2. for the second hour (of the SAME flight, ie the flight has to be continuous  with the first)  alternate between 65% and 75% power every 15 minutes. Again fly the aircraft as in 1.
3. for the last half hour of the above flight, (ie you minimum flight length will be 2.5 hours) fly the aircraft at maximum power for 30 mins.
4. land the aircraft, check for oil leaks and "change the oil" (not sure about oil change). 

This will stop glazing on the cylinders as the rings will be worn in.  
Hope this clears up the glazing confusion.   

At what RPMs for 1&2?
At what altitude for 3?

[Nomad Pilot]

When someone mentions low CHT, as a mechanic I would ask about oil temp. A combo of Low CHT and oil temp might lead me to believe he’s on the back side of BSFC. The OP mech mentioned oil pooling and possible cylinder glazing and was questioning low CHT. The mechanic should have started asking a few questions of how the pilot manages the engine so the answers can lead him to a possible problem or a tweak in engine management.


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[jaylw314]

1 hour ago, Nomad Pilot said:

When someone mentions low CHT, as a mechanic I would ask about oil temp. A combo of Low CHT and oil temp might lead me to believe he’s on the back side of BSFC. The OP mech mentioned oil pooling and possible cylinder glazing and was questioning low CHT. The mechanic should have started asking a few questions of how the pilot manages the engine so the answers can lead him to a possible problem or a tweak in engine management.
 

I've got to imagine OAT has a larger effect on low oil temp than how far LOP you run.  Both the OP and @Marauder are apparently flying in the norther tundra, presumably with non-winterized oil coolers.  I can barely crack an oil temp of about 200 degF on full power climbs in the summer heat, even with CHT's above 380 degF, so those oil coolers must work pretty well...

I also have a hard time imagining that most IO-360's are capable of being run smoothly in the 75-100 LOP region that has the increased BSFC?  

13 hours ago, Nomad Pilot said:

If your running on the backside of BSFC, your doing harm to the engine.

Do you have any specific evidence to support the claim that "deep" LOP is harming the engine in some way that normal LOP doesn't, or is this the 30+ year A&P experience? 

IIRC, on engines that are approved to run LOP, I don't remember a specific limitation on HOW far LOP.  In fact, the Cirrus SR22T AFM addendum referencing approved LOP operations states that while the FF shows a "target FF" in the 50-75 degF LOP range, it also specifically states "Other than lower cruise power, the only undesirable affect of an overly lean-of-peak setting is engine misfire".