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Expected Turbocharger Time before Overhaul


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How many hours should an M20K Turbocharger last before overhaul or replacement? 

I am planning to purchase an M20K, which has a Merlin Wastegate and TurboPlus Intercooler.

The aircraft currently has an overhauled turbocharger with 532 hours on it since it was installed.  

Any insight will be greatly appreciated.

Thanks

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Lots of discussion on proper operation of turbos going on...

Many people are very particular to controlling TIT...

Making sure the oil flow works is key... oil is the coolant and the lubricant....

OWTs around idling to allow the turbo to cool have fallen by the wayside...

I can invite a couple of K owners that have discussed the topic before... @jlunseth @Yooper Rocketman and @aviatoreb

Expect a well cared for turbo to last a very long time...

Over heated ones have a tendency to suffer from blade elongation and contact with the case... turning the blades into nubs...

Burnt oil has a tendency to block the oil flow, generating more burnt oil until the passage becomes blocked...

The K has a few challenges for best operation... not so many for early OHs...

When buying a TC’d engine... become very familiar with exhaust systems... this is where wear, and V-band clamps can be hazardous... more on that later...

This should help get things started...

Best regards,

-a-

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I had mine overhauled at somewhere between 600 & 700 hrs. on the engine. I think the engine had been run pretty hard before I got the plane. Currently the engine is at a hair over 2000 hours, so the turbo has somewhere around 1350 hours. The last several hundred hours I have run LOP quite a bit at cruise, which for me is 34” MP, 2450 RPM, 11.1 GPH. My target upper limit for this setting is 1600 dF. When I started doing that I was concerned I would be working the turbo pretty hard. Doesn’t seem to be the case. Last year I had my A&P (Oasis Aero at Willmar) give it a good going over and borescoping thinking it was time to rebuild again. They said it is fine.

My take? Your mileage may vary but if you avoid overheating it, it will last a very long time. The JPI is probably responsible for good care. On a handful of occasions over the years I have neglected to make the mixture full rich on takeoff. The JPI starts flashing at me very soon.

I do two preflight checks on it. I inspect it through the inspection door and I push on the exhaust to check for movement in the connections. Occasionally I also rub my finger inside the exhaust to see if the grit is dry or greasy. Dry is good, greasy means a possible oil leak in the turbo. Other than that, I watch the temp on my JPI often.

Footnote, the CDT redline is somewhere around 275, I don’t remember anymore. I learned early on that CDT is to protect the engine from predetonation, it is not to protect the turbo. That seems to be true. I have the intercooler, which means that Induction Air Temp is much lower than CDT, making CDT pretty much irrelevant. It is a non-event if the CDT goes over redline. I have seen that a few times.

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I just had mine rebuilt due to too much play in the turbine shaft. It has 1400 hours or so and original to that engine. No issues or oil burning noted, but an overzealous mechanic deemed it needing overhaul. I suppose better to overhaul before it started grinding the housing, but felt it a little premature.

Note that mine is a 262 with the MB engine and is a different turbo than that in the LB and GB.

 

Adding some further context: I run LOP and keep it less than 1600. but no CDT on mine. Not sure with the previous owner did.

Edited by milotron
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So, what can go wrong with a turbo? The turbine housing can crack, the compressor housing can crack, although I would imagine that is rare. The turbine wheel can get damaged by over temping the turbo. The shaft and bearings can wear out. The compressor wheel can get damaged if something gets past the air filter.

Other than the bearings and shaft, nothing really wears out. 
 

Every problem with my turbo was discovered by inspection. It doesn’t seem like having a functioning turbo overhauled before TBO doesn’t do much for you. 
 

I would be interested In other peoples experience with turbo failures, and what symptoms led them to overhaul them early.

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Incredibly helpful feedback.  I fly via AA to Prescott Sunday.  The stars are beginning to align.  Assuming all goes well, I will be flying the Mooney from Prescott to Huntsville AL towards the end of next week, … 

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1 hour ago, shoyt said:

Incredibly helpful feedback.  I fly via AA to Prescott Sunday.  The stars are beginning to align.  Assuming all goes well, I will be flying the Mooney from Prescott to Huntsville AL towards the end of next week, … 

I’ve made that trip a few times. It is a long trip, but an easy one. I worked on some equipment at the army metrology lab at the arsenal. 

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13 hours ago, N201MKTurbo said:

So, what can go wrong with a turbo? The turbine housing can crack, the compressor housing can crack, although I would imagine that is rare. The turbine wheel can get damaged by over temping the turbo. The shaft and bearings can wear out. The compressor wheel can get damaged if something gets past the air filter.

Other than the bearings and shaft, nothing really wears out. 
 

Every problem with my turbo was discovered by inspection. It doesn’t seem like having a functioning turbo overhauled before TBO doesn’t do much for you. 
 

I would be interested In other peoples experience with turbo failures, and what symptoms led them to overhaul them early.

This was automotive (track car), but was the result of a cascading failure caused by a spark plug core separating, which led to a valve failing (from getting beaten up by the spark plug pieces), which led to a piston partly disintegrating.   The debris from all that got distributed around into all of the cylinders via the intake manifold and various small pieces of everything that got beaten up eventually went out the exhaust and through the turbo turbine. 



No photo description available.

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13 hours ago, N201MKTurbo said:

So, what can go wrong with a turbo? The turbine housing can crack, the compressor housing can crack, although I would imagine that is rare. The turbine wheel can get damaged by over temping the turbo. The shaft and bearings can wear out. The compressor wheel can get damaged if something gets past the air filter.

Other than the bearings and shaft, nothing really wears out. 
 

Every problem with my turbo was discovered by inspection. It doesn’t seem like having a functioning turbo overhauled before TBO doesn’t do much for you. 
 

I would be interested In other peoples experience with turbo failures, and what symptoms led them to overhaul them early.

When I bought my aircraft it had a cracked turbo that was not repaired as it should have been by the prior owner. I just took care of it myself. The crack was through the upper and lower decks. The exterior sign of it was a grayish powder on the outside of the housing. That was a long time ago. That and other engine problems led me to believe the prior owner had run the thing pretty hard. I don't pamper it, my LOP cruise is 71% power and I have taken it into the flight levels quite a bit, where cooling is not very good. I have to say, the turbo seems very durable and pretty much maintenance free if you don't look for ways to kill it, like leaning on takeoff. 

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24 minutes ago, gsxrpilot said:

One other note on this... I never sit and "let the turbo cool down". For anyone still thinking this is a thing, it's been thoroughly debunked by the APS guys. 

I just land, taxi to my hangar or parking, and shut down.

+1

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Well - I decided to overhaul my turbo - when - as it turns out - it failed catastrophically during a flight - enroute at 16000 ft and caused me to make a very scary but happily successful emergency landing dead stick to an airport that was attainable in part because of the altitude and long glide abilities of Mooneys.  That story is here somewhere - search either saki, or Holy Yikes!

Knock on wood.

I am hoping to change my next turbo before getting "maximum" service out of it like I did last time.

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2 hours ago, GeeBee said:

After running a fleet of C402 freighters the biggest problem in turbos is shaft coking. Another reason to move to unleaded fuel. Shaft coking is nearly non-existent with synthetic lubrication.

 

 

The RaJay turbos used on 231s (and turbo 201s) has a dual sleeve shaft bearing that is practically immune to that problem. 
 

I was talking to the turbo shop recently and he said that he can overhaul one of those giant twin Cessna turbos for half the cost of one of our little RaJays.

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6 hours ago, EricJ said:

This was automotive (track car), but was the result of a cascading failure caused by a spark plug core separating, which led to a valve failing (from getting beaten up by the spark plug pieces), which led to a piston partly disintegrating.   The debris from all that got distributed around into all of the cylinders via the intake manifold and various small pieces of everything that got beaten up eventually went out the exhaust and through the turbo turbine. 



No photo description available.

Can’t blame that on the turbo! I bet that turbo was still making boost.

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14 minutes ago, jlunseth said:

How many hours were on it Erik. Do you know?

Just shy of 900 hrs.  They say 1000 is a magic number.  But my thought is it did have a period of inactivity several years before I purchased.  I had made a thorough inspection of the engine and it checked out beautifully. I have 1100 hrs on my engine since I purchased so the the checks of cylinders and lowers was legit.  But its hard to look inside a turbo.  They say turbos themselves hate inactivity.  I have always operated the engine carefully with temps carefully monitored but who knows about the prior?  Anyway - I learned a lot.  

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My 231 with a similarly configured Merlyn and intercooler has 1500 SOH on the engine including the cylinders and turbo.  
 

Having a great engine monitor and operating the components with good margins can certainly help out with longevity.  Knowing how it has been operated can be one of the better indicators of when to expect overhauls.  The factory gauges are terrible on the 231’s if you like engine and component longevity. 
 

I plan to overhaul my turbo when the engine goes out for overhaul one of these years. 

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