Over boosting and High cylinder temps

[MattSet]

Long story short.   Purchased a 1982 M20K 231 with an intercooler and automatic waste gate.    Annual complete.  Plane has not flown for 2 years.  But on first flight.   At 100 feet over a short runway. Engine had a bad vibration like water in fuel, cleared up after a few seconds but sure got my attention.  Manifold pressure on take off was 42.  Backed it down to 35.    Cylinder temps very high.  Number 2 reached 498.    Backed manifold pressure down to 25 before able to cool the temps to normal ranges.  With number 2 still the hottest at 380 or so.   Decided to circle airport and land.  
 Question is.  Would not the  automatic waste gate keep the engine from over boosting?  If working properly.

And why would the cylinder temp still be very high at 35 inches pressure and had to drop to 25 to bring temps back to normal.    And this was on a 35 degree day.     
 Yes during annual, removed and cleaned all injectors.  
Also.  Who is the best A&P for this type of issue in the South east. 

[Ragsf15e]

10 minutes ago, MattSet said:

Long story short.   Purchased a 1982 M20K 231 with an intercooler.    Annual complete.  Plane has not flown for 2 years.  But on first flight.   At 100 feet over a short runway. Engine had a bad vibration like water in fuel, cleared up after a few seconds but sure got my attention.  Manifold pressure on take off was 42.  Backed it down to 35.    Cylinder temps very high.  Number 2 reached 498.    Backed manifold pressure down to 25 before able to cool the temps to normal ranges.  With number 2 still the hottest at 380 or so.   Decided to circle airport and land.  
 Question is.  Would not the  automatic waste gate keep the engine from over boosting?  If working properly.

And why would the cylinder temp still be very high at 35 inches pressure and had to drop to 25 to bring temps back to normal.    And this was on a 35 degree day.     
 Yes during annual, removed and cleaned all injectors.  
Also.  Who is the best A&P for this type of issue in the South east. 

Does it have an automatic wastegate?  They didn’t come with one.  You said it has an intercooler, but the “wastegate”might still be the throttle in your hand if one wasn’t added via stc.

What was fuel flow on takeoff?  What temps did the other cylinders get to?

[MattSet]

Yes.  It has an Automatic waste gate.  I did not take note of fuel burn and the other cylinder temps were running about 50 degrees less.  I also engaged low boost fuel pump on takeoff

[Ragsf15e]

4 minutes ago, MattSet said:

Yes.  It has an Automatic waste gate.  I did not take note of fuel burn and the other cylinder temps were running about 50 degrees less.  I also engaged low boost fuel pump on takeoff

Do you have an engine monitor to download the fuel flow on takeoff?  That would help you know if the engine is set up correctly.  

[MattSet]

 Not that I know of.  I checked the engine monitor I have and it does not down load.   That was the first thing my pilot and I tried to do.  But she is a little dated for that.  Definitely planning to update her.  Just need to get her home safely first 

[kortopates]

Yes.  It has an Automatic waste gate.  I did not take note of fuel burn and the other cylinder temps were running about 50 degrees less.  I also engaged low boost fuel pump on takeoff

There is nothing automatic about the Merlyn wastegate- which i assume you are referring too. it’s still 100% manual.
You can still easily overboost the engine.
To be automatic you need the -MB engine as in a “262” conversion. The picture shows a 231 engine.

What you describe though sounds like detonation and your max FF is likely insufficient. Watch out for TIT exceeding 1450F on takeoff indicating insufficient fuel flow.
Lastly with the intercooler, max or redline boost should be about 37.5”. It’s up to the pilot to add throttle slowly above 30” to avoid over boosting.


Sent from my iPhone using Tapatalk

[Ragsf15e]

22 minutes ago, MattSet said:

 Not that I know of.  I checked the engine monitor I have and it does not down load.   That was the first thing my pilot and I tried to do.  But she is a little dated for that.  Definitely planning to update her.  Just need to get her home safely first 

@kortopates is way better than me at this point, but the Merlin may be “automatic” only in that it holds MP steady(or steadier) as you climb, but it will hold it steady at whatever you increase the throttle to, even way higher than it should.

[PeteMc]

12 minutes ago, kortopates said:

There is nothing automatic about the Merlyn wastegate- which i assume you are referring too. it’s still 100% manual.

Not following you on this one.  There are no manual controls for the Merlyn Black Magic.  It simply measures the difference between the upper deck pressure and manifold pressure and adjusts accordingly... so, what I would call an "automatic" device.   Granted, not the same system that is in the 252, but still no leaver to push or pull to "manually" adjust the wategate. 

 

[gabez]

I think you need to read the POH and the supplement with the intercooler. With the Marylin you are still able to overboost, and you did read this thread (

).

 

Additionally, and here folks have to check me (since I don't have one), the intercooler take off MP is more like 36 as you are getting more cold air in. 

So basically you overboost the crap out of that plane, no wonder why you hit 498. There maybe some damage done 

[PeteMc]

1 hour ago, MattSet said:

Would not the  automatic waste gate keep the engine from over boosting?  If working properly.

The Merlyn Black Magic can easily over boost pending what altitude you are at.  I used to fly out of a airport at 79ft MSL, so if I quickly cranked in full throttle, as soon as the turbo spun up it could go way past 40".  So for a basic Takeoff with the 231 and the Merlyn are to slowly bring in the power and let the turbo spin up an then set your TO power.. and then check it again after a few seconds.  Whether you're comfortable at glancing over before TO of if you want to do it right after TO, but do check.  

And if you fly around the country, it will be different as you are departing Airports at different elevations.  So never go with muscel memory to assume you've got the right power setting for TO because you pushed the throttle in the same amount you always do at your home Apt. 

[MattSet]

I believe you are correct.  When it felt like water in fuel, rough running.  I noticed manifold pressure at 42 and said to my pilot.  Manifold is 42.   He reduce throttle and got it below 38 and the roughness cleared up quickly.  He said he wasn’t watching it as he thought the auto waste gate would handle any over boost.  We were in climb out in a critical area.  Once up safe to an altitude he reduced it more.  But it took 25 to bring all the temps to normal.    

[Guy123]

I am going to guess you have at least 2 problems.   

As pointed out earlier sounds like you were probably running LOTS of power with unknown fuel flow. Probably not enough. My understanding is fuel flow is what keeps these engines cool.  This is the first problem that needs attention.

Later after you get the primary problem figured out, I'm guessing you will probably still have trouble keeping it cool in the summer in cruise.    From your picture it kinda looks like your baffle seals are in need of some attention.  Hopefully other more experienced members will weigh in and let you know if they are seeing the same thing as me from your picture. 

[Falcon Man]

Do you or your AP/IA have a copy of the TCM TSIO360 maintenance and OH manual? IThere is a copy in the downloads section.

Additional things worth checking are:

1)  Fuel flow at max rated MP for your engine type - GB, LB?

2) Once FF is in the correct zone, perform a GAMI lean test flight to see what the FF spread is. Ideal would be no more than 0.5 gph spread.

2) Are the metal cylinder baffles installed correctly?

3) It looks like there is a lot of surface corrosion on the engine and induction tubes. You may have an induction leak as the seals between the tubes are off color and may be leaking.

4) At cooler OAT's and sea level the MP can easily overboost on the GB/LB engine. Has to be controlled by the pilot via throttle as earlier mentioned.

5) Overboost can destroy the lower end of the engine in short order. Consider draining the oil and check the filter for metal. Also a borescope can be put up thru the oil sump drain hole to look around for damage.

 

 

 

 

 

[MattSet]

Thank you all for your input.  We tested compression again.  All in the low 70’s.   Borascoped the cylinders and the A&P said they were the cleanest he had ever seen and found no issues with valves or with anything in them, guess running it hot for a few seconds on take off burned out any carbon LoL.    After careful review we have tested and found no issues with fuel flow for each cylinder, all even flow from the spider and decided to order a set of Gami injectors to even out cylinder temps and to keep the manifold pressure 36-38 on take off. 

[Ragsf15e]

3 hours ago, MattSet said:

Thank you all for your input.  We tested compression again.  All in the low 70’s.   Borascoped the cylinders and the A&P said they were the cleanest he had ever seen and found no issues with valves or with anything in them, guess running it hot for a few seconds on take off burned out any carbon LoL.    After careful review we have tested and found no issues with fuel flow for each cylinder, all even flow from the spider and decided to order a set of Gami injectors to even out cylinder temps and to keep the manifold pressure 36-38 on take off. 

Just be careful about total ff.  If that’s not set at the upper end of the takeoff range, you will quickly end up too hot.  Yes, balancing ff with injectors is nice, but you need max ff at full power to keep these engines cool.  Too low will also be evident in a higher tit as @kortopates mentioned.

[Pinecone]

Does your mechanic KNOW how to set up a Continental fuel system?  It is not the same as a Lycoming.

[WilliamR]

4 hours ago, MattSet said:

 After careful review we have tested and found no issues with fuel flow for each cylinder, all even flow from the spider and decided to order a set of Gami injectors to even out cylinder temps and to keep the manifold pressure 36-38 on take off. 

As noted, the balance of flow is not what people were talking about. The concern was/is takeoff power total flow. 

Not sure what GAMI's will do with cylinder temps although maybe you mean exhaust gas temps. Also not sure how GAMI injectors would impact manifold pressure. Not sure what engine data set you sent GAMI either. Obviously, it wasn't the short flight where you just about blew up the engine (sorry to be tough but that is very much a risk).

Without being harsh and based on what you've written so far, you really need to find two things:

1. A mechanic who understands turbocharged engines. Even better would be someone who has experience with these older version small block turbo Conti's and understands the variations of turbo Conti's setups wrt wastegate, fuel and air intake, and intercoolers. Unfortunately, I don't have any mechanic references. 

2. A sharp pilot/instructor who understands turbo charged engines and has access to the supplements and POH for operating said engine who can teach you how to operate the engine. Actual experience would be even better.

I only have a few thousand hours in various turbo piston engines including as a CFI, but what you've written is very scary to me. I don't write that lightly.

I get you don't know what you don't know, but you really need a good resource. Lots of really good instructors available who know and have experience in this engine including the aftermarket setup. Seek them out. 

Best of luck

William

Btw, I would also check the sparkplugs. Those are usually the first to go in a detonation event like you seem to have had. See recommendation 1 above.

[kortopates]

Excellent recent advice above by @WilliamR and @Ragsf15e about what the priority should be - max FF not Gami's, which I am sure is why @Pinecone is asking about your Fuel set up. Since this is a 231 with an aftercooler, it needs to get the max FF specified by both TCM and the aftercooler manufacturer at the reduced redline MAP (generally about 37.5" MAP depending on manufacturer) not the original 40" - which many mechanics without experience with this engine fail to do.

I teach my transition students to monitor TIT as they go to full power and start the takeoff run and abort any takeoff if they see the TIT get to 1450F - with countless Savvy clients I've see a partial loss of power occur after takeoff from this. The K's didn't get this warning their POH's but its in every modern Continental turbo engine POH to flip on the boost pump if TIT gets to 1450F.

So make sure max FF is adequate at your max MAP.

Secondly find an instructor that actually has time in type including a 231. Its critical and almost cost you your engine from overboost - if it got a couple inches higher I am sure it would have been much worse.

If I had more time I would provide a better explanation on Merlyn's limitation. But @PeteMc actually did a fine job of explaining why it's not an "automatic" wastegate. An "automatic" wastegate is also known as a "set and forget" wastegate. Its flies just like a NA engine and won't overboost as your CFI pilot expected. This is where the marketing material on Merlyn's website is so misleading and you and your CFI are not the first to misunderstand this since anyone with real turbo experience reads automatic wastegate expects exactly that - a set and forget. But the Merlyn is sill manual, as Pete explained, it will still overboost and as ambient atmospheric pressure changes in climbs and descents you have to keep adjusting the throttle for MAP setting you want. How the throttle behaves is no different than how the throttle behaves without the Merlyn, but what the Merlyn brings to the table is "adjustable" wastegate over the original fixed bolt. By adjusting the wastegate, it's able to greatly increase the critical altitude of the turbo installation from 15K DA to around 22K DA, which does make it a whole new airplane with respect to altitude performance. But the pilot still has to manually manage their MAP after any change in ambient atmospheric pressure or altitude unlike any real automatic wastegates which are all hydraulically controlled wastegates. However, given the price point for a Merlyn pneumatic wastegate, its a bargain compared to how much a hydraulic wastegate installation adds up to in 252 or Encore which is why most 231 pilots are happy with its limitations. I originally owned a 231 as well before upgrading to 252 now converted to the Encore - but night and day differences.

[kortopates]

Since your in FL, although its probably too late now, but you could learn a lot about your Mooney by attending our next PPP in Ocala FL weekend after next Jan 30, see https://www.mooneysafety.com/event-details/ocala-florida

We do a 5 across the country each year so maybe you can join us at a future one,

Edited January 21 by kortopates

[jrwilson]

9 hours ago, MattSet said:

Thank you all for your input.  We tested compression again.  All in the low 70’s.   Borascoped the cylinders and the A&P said they were the cleanest he had ever seen and found no issues with valves or with anything in them, guess running it hot for a few seconds on take off burned out any carbon LoL.    After careful review we have tested and found no issues with fuel flow for each cylinder, all even flow from the spider and decided to order a set of Gami injectors to even out cylinder temps and to keep the manifold pressure 36-38 on take off. 

I think redline is 37” with intercooler…so maybe keep it lower.  I use 36” as max takeoff power.  

[kortopates]

Hi @MattSet I keep forgetting to point out that from your picture it sure looks to me like you still have the TCM Diverter valve on your Mooney. Back in 2019 TCM issued Critical Service Bulletin CSB19-01A  for fuel diverter valve malfunctions, requiring owners to remove the assembly and reroute fuel to prevent power loss, a critical safety issue due to potential leaks and hydrostatic lock. Apparently it brought down at least one plane. This never made it too required AD status but nevertheless its been taken seriously enough we only rarely see one still in the field - especially after all these years. 

Recommend you verify if it hasn't been complied with implement it soonest if so. After sitting for a couple years the seals in the diverter are even more likely to cause an issue in flight. 

[gabez]

16 hours ago, MattSet said:

Thank you all for your input.  We tested compression again.  All in the low 70’s.   Borascoped the cylinders and the A&P said they were the cleanest he had ever seen and found no issues with valves or with anything in them, guess running it hot for a few seconds on take off burned out any carbon LoL.    After careful review we have tested and found no issues with fuel flow for each cylinder, all even flow from the spider and decided to order a set of Gami injectors to even out cylinder temps and to keep the manifold pressure 36-38 on take off. 

so please read about GAMI. 1. they may actually not do anything out of the box, you need to go through a process and potentially swap the injectors to level them. I would actually not touch the injectors. Spend time making sure the FF at take off is what it needs to be and the temps are right at take off, cruise and descent. GAMI won't do magic 

[PeteMc]

12 hours ago, kortopates said:

But @PeteMc actually did a fine job of explaining why it's not an "automatic" wastegate.

Sorry...  I still say you're wrong on this one.

au·to·mat·ic
1. (of a device or process) working by itself with little or no direct human control.  

Merlyn Products, Inc. "...A pneumatic operated controller automatically senses engine parameters and adjusts to maximize engine and turbocharger efficiency..."  Note they also refer to it as "automatic" in their description.

I have never once "adjusted" my Merlyn Black Magic, nor do I have a manual control to do so if I wanted to.  I get that it is different device than what you describe as "set and forget" wastegate in later Mooneys.  And yes, they are an imporved device and prevent overboosting, but preventing overboosting is not the definition of automatic.  And just because the Merlyn, or any other device,  may have operational limitations, it does not excude them from being "automatic." 

[Will.iam]

On 1/22/2026 at 1:37 AM, PeteMc said:

Sorry...  I still say you're wrong on this one.

au·to·mat·ic
1. (of a device or process) working by itself with little or no direct human control.  

Merlyn Products, Inc. "...A pneumatic operated controller automatically senses engine parameters and adjusts to maximize engine and turbocharger efficiency..."  

And that right there is the fallacy and false misleading. For maximum engine efficiency for takeoff would be 36-37 inches of manifold pressure but it doesn’t automatically goto or adjust to the pressure. It goes right up to 42 inches and stops there only necause your safety blowoff valve opens to keep the pressure from going higher. Now compare that to the MB engine where you shove the throotle full forward and the turbo boost controller maximizes the manifold oressure to exactly 36” of pressure and maintains that 36” all the way up to 24,000ft. Where as the Merlin controller starts losing manifold pressure as you climb requiring throttle readjusting every couple of thousand of feet to maintain your set 36” mp. Same issue going down. I do not touch my throttle from FL to pattern altitude but a 231 has to keep pulling back on the throttle as you descend as the air gets thicker and you the pilot have to make those MANUAL adjustments not like the 252 where the wastegate makes that adjustment automatically for you. 

[PeteMc]

2 hours ago, Will.iam said:

but it doesn’t automatically goto or adjust to the pressure.

WRONG!  You are stating that because one device does not work/perform the same way as a different device that it is not an "AUTOMATIC" device.  Sorry, it doesn't work that way. 

Show me the MANUAL CONTROLS on the Merlyn Black Magic and I will then agree it is not an AUTOMATIC device.  

I am not disputing that the Wastegate on the MB is a better device.  But that is not the question here.  There are no smoke and mirrors, I change the power on my LB and the Merlyn, by itself, adjusts.  So that would... say the word with me... make it automatic by definition.   Sure, if I go outside of the operating range of the Merlyn it cannot keep up with the changes I've made (e.g. craming in full throttle at sea level) or an over boost or a fast descent from altitude. 

But I'm perplexed how a few of you belive operating outside of a devices range suddenly makes it a "manual" device.  I delt with various "automaic" audio and video controls for decades that could be pushed passed their limits.  But none of us (engineers or operators) would suddenly start calling it a "manual" device since it wasn't.  Sure, you occasionally would get beyond the operating limitations and someone would "manually" have to bring it back into range, but then it would continue to perform its "automatic" functions as designed.  The Merlyn is no different.  

 

Edited January 25 by PeteMc