Engine temps

[Steven B]

Can anyone tell me the accepted temperatures for cruise in the M20 K Continental TSIO 360 engine, I heard anything on CHT from 380 to 440. That seems like a huge range to me. Would love to know a standardized acceptable range for cruise in the CHT/EGT/TIT if possible. Thank you in advance for all of your expertise. 

[hubcap]

My personal practice is to keep the CHT under 380 degrees at all times. If mine are at or above 380 degrees I am doing something to bring them down. 
 

With proper use of cowl flaps, mixture and manifold pressure, it is not a problem to keep them below 380 degrees even in the summer. You may sacrifice a little speed, but I try to take the best care of my engine that I can.

I keep my TIT around 1550 degrees in cruise. I almost always fly lean of peak in cruise.

The resident expert on the 231 is @jlunseth so maybe he will show up and give his .02.

[Steven B]

Thank you for the input. Exactly how I’ve been flying. Although I’m always a bit shy to fly LOP. I feel like gas is cheaper than cylinders but that’s probably just my insecurity!  Thx again!

[jlunseth]

The CHT book limit for the 231 engine is 460 but you should not ever get near that number. My target is also 380, although there are circumstances where I will see higher temps. I fly for Angel Flight which takes me pretty much all over the country except the west side of the Rockies. I will see higher temps in a high hot climb especially from a western airport, e.g. Montana, Colorado, the western Dakotas and the like. My plane is getting a new engine (the old one was 20 years old and several hundred over TBO) and hopefully better baffling, so maybe I will get lower temps from the new engine. 380 is pretty typical at cruise but one or two cylinders would creep up over 400 in those high hot climbs. I keep my climb rate at about 500 fpm partly for passengers ears and to keep the climb temps down. A problem with the 231 is getting your A&P to set the fuel flow high enough. Invariably, when mine would come back from annual, the full rich flow would be 22 something. It really needs to be about 24. I fly LOP quite a bit. 34” MP, 11.1 GPH, 2450 is my standard cruise setting. That works well up to somewhere around 12-16k (depends on OAT), where TIT will become difficult to control. The keeps the CHTs nice and cool. It gives me 71% HP and nifty speeds.

[Pinecone]

I will join the chorus and say I maintain my CHTs below 380.   And I keep my TIT below 1600, preferably lower.

I run LOP.  LOP will NOT harm your cylinders.  If anything, it helps their life.

I also run below 65% power, typically cruising at about 10 GPH which is 62%% on my -SB.  A few minutes are cheaper than cylinders.

A couple of months ago, this translated to 175 KTAS at 17K, 7 hours Denver to NE MD non-stop on about 80 gallons.

[Z W]

CHTs below 380.  Easy to maintain even in climb if you climb full power and about 120 KIAS.  Plenty of air and fuel to cool the cylinders.  If one creeps up, I have an alert set in the panel at 380, and just level off for a moment.  Climbs in the teens on warm days do sometimes result in temperatures creeping up towards 400.

Open and close the cowl flaps as required to maintain CHTs under 380 in cruise.

My plane's TIT runs hotter than most seem to post here, and it does not run smooth LOP.  I keep it under 1625 TIT, as close to 1600 as I can get, which varies with ambient temperatures.  Usually flying 27-28 MP, 2500 RPM, 12-13 GPH.  Gives me 135-140 KIAS, which is 150-185 KTAS, depending on altitude.  Somehow that's always 5-10 knots slower and 2 GPH higher than all the other posters with the same engines and airframes but I think the internet adds 10 knots and subtracts 2 GPH.  Your experience may vary.

Keep in mind also some are using the old factory TIT and CHT gauges, some are using modern glass panels and sensors of different varieties, and some are more sensitive to feeling or noticing LOP "roughness" than others.  I think we each pick our own comfort zone and hope for the best.

[Steven B]

Thanks for the info. When you say “full power,” do you mean firewall the throttle, or full power as recommended by the POH. My POH says never go above 38 inches. Firewall would probably be 40, which I never do. TYIA. Btw I have the 81, m20 k with a merkin black magic waste gate. 

[Pinecone]

44 minutes ago, Z W said:

but I think the internet adds 10 knots and subtracts 2 GPH.  Your experience may vary.

Keep in mind also some are using the old factory TIT and CHT gauges, some are using modern glass panels and sensors of different varieties, and some are more sensitive to feeling or noticing LOP "roughness" than others.  I think we each pick our own comfort zone and hope for the best.

Which is why I post pictures.

I have a JPI 830 and the stock TIT setup.  A while ago I noticed that for the same power setting, the factory TIT was reading lower and lower.  But the JPI was about the same as always.  So I had my shop replace the TIT probe and suddenly, the JPI and factory guage are very close.

The failure mode of the TIT probe is to read lower than actual.  

[Fly Boomer]

On 8/28/2023 at 2:24 PM, Steven B said:

Can anyone tell me the accepted temperatures for cruise in the M20 K Continental TSIO 360 engine, I heard anything on CHT from 380 to 440. That seems like a huge range to me. Would love to know a standardized acceptable range for cruise in the CHT/EGT/TIT if possible. Thank you in advance for all of your expertise. 

440 (or probably anything in the 400 range) will get expensive.  LOP generally produces lower temperatures, not higher.  If your engine will tolerate LOP (plugs, wires, magnetos, GAMIJectors, etc.) you can generally get lower temperatures by going leaner.  But you have to know when you are LOP and how to get there.  Best knowledge base is a live class at APS in Ada OK.  Second best is online class at APS.  APS is another business run by the GAMI guys.

https://www.advancedpilot.com/

[Steven B]

That’s great information. Thank you so much 

[jlunseth]

3 hours ago, Steven B said:

Thanks for the info. When you say “full power,” do you mean firewall the throttle, or full power as recommended by the POH. My POH says never go above 38 inches. Firewall would probably be 40, which I never do. TYIA. Btw I have the 81, m20 k with a merkin black magic waste gate. 

No, not firewall. I generally use 36” and 2700 RPM as full power. The 36”, as best as I can determine, comes from an old article on the 231 which suggests using that. Actually, full power appears to be in the vicinity of 37”. That comes from the Turboplus intercooler STC, which modifies the instructions for setting the full power fuel flow. According to the STC, full power varies depending on OAT at the ground when the work is done, but generally the number is 37”. I use 36, but if the power rises toward 37 I just let it. (The fuel flow does tend to rise on takeoff because airspeed is changing.) Although it seems counterintuitive, if you are doing a high hot climb and have an intercooler in a 231, it may help cool the engine a little to set power at 37 rather than 36 or lower, because the fuel flow will come up with the increased MP, and you need more fuel flow.

If you do not have the Turboplus in your aircraft, full power is 40” and 2700. 

The MP only ever gets firewalled if you attain and/or exceed Critical Altitude, which varies a little with the day, but is about 22,500 in my Merlyn equipped engine. It will be quite a bit lower in the non-Merlyn equipped engine.

The Merlyn does not affect the full power setting, the intercooler does affect that setting.

[jlunseth]

It is worth saying that while I agree completely with FlyBoomers statement that LOP yields lower CHTs, if you come from a mainly Normally Aspirated background, you need to understand that does not apply to climb. LOP in climb in a turbo will generally yield bad things, such as high temps. There is an NA technique - leaning in the climb - that has no application in turbos frankly. The difference is that the NA makes less and less power, and will experience a lower and lower MP as it climbs, and if fuel flow is not changed the mixture will get richer. In the 231, we also experience a reduction of power in the climb because the wastegate controller is not a truly automatic one, it does not maintain a set MP. But we pilots do, we adjust the MP in and we are back at full MP. Effectively, the engine does not experience a reduction in MP and therefore does not need a downward adjustment in fuel flow. The engine needs full fuel flow at full power (plus open cowl flaps and a decent airspeed) to stay cool in a prolonged hot climb.

[Steven B]

Thank you. All super helpful information. I have that exact setup. 231/merlin fixed wastegate(black magic? I think). And I use about 36/2700 on takeoff. The difficult part is there are a lot of opinions that are conflicting. Example, I had my fuel flow set and the AP told me the book says full power and wanted me to firewall the throttle which I had never done, nor work I.from what I understand full power and firewall are different (at least in that plane). Subsequently I found another mechanic. But for a naive pilot who’s fairly new to Mooney’s, I could have easily followed his misinformation and damaged my engine. I sincerely appreciate all your guidance!

[Shadrach]

1 hour ago, jlunseth said:

It is worth saying that while I agree completely with FlyBoomers statement that LOP yields lower CHTs, if you come from a mainly Normally Aspirated background, you need to understand that does not apply to climb. LOP in climb in a turbo will generally yield bad things, such as high temps. There is an NA technique - leaning in the climb - that has no application in turbos frankly. The difference is that the NA makes less and less power, and will experience a lower and lower MP as it climbs, and if fuel flow is not changed the mixture will get richer. In the 231, we also experience a reduction of power in the climb because the wastegate controller is not a truly automatic one, it does not maintain a set MP. But we pilots do, we adjust the MP in and we are back at full MP. Effectively, the engine does not experience a reduction in MP and therefore does not need a downward adjustment in fuel flow. The engine needs full fuel flow at full power (plus open cowl flaps and a decent airspeed) to stay cool in a prolonged hot climb.

For those of us that fly NA Lycomings, The RSA fuel injection does reduce FF as available MP decreases.  The system is not perfectly precise, but it does hold a ballpark air/fuel ratio once set by the pilot. The mixture does not really get richer and richer so much as the mixture set at lower altitude is more rich than needed for the power produced as MP decreases in climb.  LOP climbs are not really worth it for a high performance single, too much fiddling with the knob for a short lived, minor gain in efficiency and reduced climb performance.  I would think the opposite would be true when you have a turbo that can hold a constant MP up to cruising altitude.  As I recall both Walt Atkinson (RIP) and John Deakin (RIP) spoke of using LOP climb settings when operating their TN'd Bonanzas. Something else must be a play.  Are you not able to run sufficiently lean to keep temps in check?  It's as if you're saying that when LOP in cruise, CHTs and ICPs are lower but not when the aircraft changes to climb pitch and airspeed. I know you don't believe that, so I am curious what the issue is.

[Fly Boomer]

14 minutes ago, Shadrach said:

As I recall both Walt Atkinson (RIP) and John Deakin (RIP) spoke of using LOP climb settings when operating their TN'd Bonanzas.

I don't have direct experience but, when I went to Ada, I think I recall that their Tornado Alley system wouldn't go to 38 inches.  Again, not sure, but I suspect that makes a difference.  The Rocket book says "balls to the wall" (or something like that) to push the most fuel.  Also, Rocket wants that Continental fuel system set at the top end of the spec, or slightly richer.  Rocket didn't like the idea of LOP when they created their documentation, but some Rocket people are able to do it.  Of course, the issue is always heat.  While I don't remember the exact question, I remember asking Deakin some question regarding the 252 at 28,000 and his one-word answer was "heat".

[Shadrach]

7 minutes ago, Fly Boomer said:

I don't have direct experience but, when I went to Ada, I think I recall that their Tornado Alley system wouldn't go to 38 inches.  Again, not sure, but I suspect that makes a difference.  The Rocket book says "balls to the wall" (or something like that) to push the most fuel.  Also, Rocket wants that Continental fuel system set at the top end of the spec, or slightly richer.  Rocket didn't like the idea of LOP when they created their documentation, but some Rocket people are able to do it.  Of course, the issue is always heat.  While I don't remember the exact question, I remember asking Deakin some question regarding the 252 at 28,000 and his one-word answer was "heat".

TAT system is not even close to 38".  It's a standard NA engine with a turbo normalizer. Max MP is likely something like 31".  Given the higher C/Rs, TIT limits are likely not an issue for the TAT system.  Those guys would run 80-85% power in LOP cruise.

My guess is that it's challenging to run high power LOP in most K models below MP redline and no one wants to climb at 65% or less.

 

[kortopates]

My guess is that it's challenging to run high power LOP in most K models below MP redline and no one wants to climb at 65% or less.
 

Exactly, K’s rarely can do better than 25-35F LOP. And TIT is typically going over 1600F at 70% and up HP.
Generally K’s are a bit better than the Bravo. But the NA and Turbo 550’s have by far the best LOP performance in that they can do 100F+ LOP easily; which well beyond what is ever required.


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[GMBrown]

2 hours ago, Steven B said:

Thank you. All super helpful information. I have that exact setup. 231/merlin fixed wastegate(black magic? I think). And I use about 36/2700 on takeoff. The difficult part is there are a lot of opinions that are conflicting. Example, I had my fuel flow set and the AP told me the book says full power and wanted me to firewall the throttle which I had never done, nor work I.from what I understand full power and firewall are different (at least in that plane). Subsequently I found another mechanic. But for a naive pilot who’s fairly new to Mooney’s, I could have easily followed his misinformation and damaged my engine. I sincerely appreciate all your guidance!

Not the expert, but as a K owner without the Intercooler or Merlyn (but soon to have the Merlyn installed) it is my understanding that the reduction to 36" for recommended max MP is for the intercooler only and there is no reason to reduce to 36" with the Merlyn only.  If you don't have the intercooler and you're running with 36" at take off, you are discarding 4 inches of MP that you could be using.

[Shadrach]

14 minutes ago, kortopates said:

 

Exactly, K’s rarely can do better than 25-35F LOP. And TIT is typically going over 1600F at 70% and up HP.
Generally K’s are a bit better than the Bravo. But the NA and Turbo 550’s have by far the best LOP performance in that they can do 100F+ LOP easily; which well beyond what is ever required.


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A lot of NA IO360s will go run acceptably at 100LOP at low altitude, there's just no operational utility in doing so. Down low in cool weather I can lean to a second EGT rise just before it starts to miss. That's typically a bit beyond 100LOP. At lower MP it gets a bit buzzy for my taste beyond about 60LOP.  So many of these engines will smoothly run quite a bit leaner than is needed for the power being produced.

[Steven B]

Yeah. I have both the Merlyn black magic fixed wastegate and the intercooler

[GMBrown]

I didn't see that you had the intercooler, so yes, you're max MP would typically be in the 36"-37" range. I haven't seen the 38" figure before but if your POH says your max MP is 38", then I would run with that.

[Steven B]

That’s exactly what the POH says. 37. I may have typed incorrectly previously. Thank you!

[Z W]

11 hours ago, Steven B said:

Thanks for the info. When you say “full power,” do you mean firewall the throttle, or full power as recommended by the POH. My POH says never go above 38 inches. Firewall would probably be 40, which I never do. TYIA. Btw I have the 81, m20 k with a merkin black magic waste gate. 

I just meant maximum manifold pressure according to your POH.  I believe with your setup, that requires you to set power at takeoff, and then slowly advance the throttle as you climb to maintain your maximum rated manifold pressure, as it will naturally decrease with altitude.  Later models with the TSIO-360-MB and TSIO-360-SB got a fully automatic wastegate, which is what I fly, and we do in fact go throttle full forward to the firewall, and the wastegate holds it at 36" of MP all the way up.  Maybe some modified TSIO-360-LB and TSIO-360-GB's are the same, I'm not sure.  But the idea is to maintain maximum manifold pressure for best takeoff and climb performance.  Never overboost your engine if it's one that's capable of doing that.

Some pilots used to (and some still do) advocate a "cruise climb" power setting where they reduce power to something like 32" and 2500 RPM, and then pitch for 500 FPM in the climb.  In my plane, that results in 1) higher CHTs due to increased angle of attack, decreased fuel flow, and decreased air flow, 2) longer climbs to altitude, 3) increased total fuel burn for the trip due to lost efficiency, and 4) higher overall trip times due to it taking forever to get to altitude.  So while I started out flying that way, I no longer do.  Full power and full rich mixture to top of climb, then reduce power and lean for cruise. 

If I'm at cruise altitude and have to go up say 2-3 thousand feet for some reason, I might use that cruise climb setting just to avoid drastic changes.  It will quickly spike your CHT's if you watch it.  If a larger altitude change than that is required I will go back to full power, full rich mixture, and cowl flaps open to help keep the engine cool and minimize the time in the climb.  You can regain all that stored energy in the descent.

Never lean in the climb, and never lean for takeoff.  That's a naturally aspirated thing.  Your turbo is always pushing full air, and so you always need full mixture.  If you lean in those conditions, you will spike your temperatures, at best, and not be making full power, or even cause your engine to shutoff, at worst.

Edited August 30, 2023 by Z W

[Z W]

11 hours ago, Pinecone said:

Which is why I post pictures.

I have a JPI 830 and the stock TIT setup.  A while ago I noticed that for the same power setting, the factory TIT was reading lower and lower.  But the JPI was about the same as always.  So I had my shop replace the TIT probe and suddenly, the JPI and factory guage are very close.

The failure mode of the TIT probe is to read lower than actual.  

I flew for long time with an old JPI 930.  It developed some issues, so we swapped it for a G500Txi.  All the readings changed significantly.  Kept the stock RPM and MP gauges and it disagrees a lot more with them than the old JPI did.  Still don't know which unit was more accurate, but on average, my true airspeed is lower if I trust the settings on the G500Txi and keep it within the limits we've been talking about than it used to be on the same settings with the JPI.  All within a few inches or degrees, but enough to make me wonder how much good we all do trying to fine tune these engines. 

[Steven B]

Thank you ZW. Such great information. I will completely follow your guidance. I think I can definitely use some help. Thanks again.