L. Trotter

Top End on Big Bore Continental (TSIO 550)

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I realize there is scattered info on this topic but would like to update / consolidate  the topic and receive some advice.

I have a (new to me) 2007 Acclaim (1100 hrs TT) no prior engine work. Now burning 1 Qt every 1.5 hrs. Cylinder pressures low 60's throughout. Some leak heard in the breather line on nearly all cylinders. Valves look good on Bore Scope. Engine runs smooth, starts easily. Plane sat for extended periods prior to purchase. I'm told I need a complete top end.

Here is an article from Mike Busch https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2014-06_cylinder-work-be-afraid.pdf which is not very flattering in regards to top overhauls. In essence, catastrophic engine failures are more likely to occur after "proper maintenance practices"! The more cylinders replaced the higher the probability-so "Be Afraid". It seems the large bore turbo Continentals typically only make it to mid-time (about 1000 hrs). OK, I'm afraid! where do I go from here? It seems top end overhauls are routine but is this the right answer? Here is a loaded question.....What have you done when faced with this dilemma? Why?

Complete Top Overhaul ? If so, with what...OEM, Superior Air Parts (Millennium), Engine Components Inc. (ECI), Aircraft Cylinders of America, or recondition my own cylinders.  Where?

Pull the engine and have complete rebuild or factory Remanufactured?

 

 

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Ok, take a deep breath. There is a lot here to deal with.

So, if it were my engine the first thing I would want to know is where is the oil going? 

You mention a whole lot of things some have nothing to do with oil consumption some may and more than others.

If your exhaust valves look good on the borescope, 60's psi on compression is not an actionable item in my opinion.

Background info would be very helpful. Operational profile, typical flight conditions. 

DOES THIS ENGINE HAVE AN OIL RECOVERY SYSTEM ? 

This is were I would start with diagnosis, don't make any decisions without all the facts you can gather.

Finally, you may want to consider joining Mike Busch's managed aircraft program. His experts will have the best knowledge and advice you will ever get.

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If you're going to replace the cylinders it is cheaper to buy a complete balanced set of 6 from Continental than to buy 6 individual ones.  If you're worried about potential risk in removing them, have your shop remove and replace them one at a time.  We do it this way, but in more than thirty years I've never experience the failure that Busch warns of.

Clarence

 

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1 hour ago, Cruiser said:

Ok, take a deep breath. There is a lot here to deal with.

So, if it were my engine the first thing I would want to know is where is the oil going? 

You mention a whole lot of things some have nothing to do with oil consumption some may and more than others.

If your exhaust valves look good on the borescope, 60's psi on compression is not an actionable item in my opinion.

Background info would be very helpful. Operational profile, typical flight conditions. 

DOES THIS ENGINE HAVE AN OIL RECOVERY SYSTEM ? 

This is were I would start with diagnosis, don't make any decisions without all the facts you can gather.

Finally, you may want to consider joining Mike Busch's managed aircraft program. His experts will have the best knowledge and advice you will ever get.

I have taken several deep breaths...with supplemental oxygen, haha.

There is no oil recovery system. The plane is new to me so I have no oil analysis history. I was told the engine burned 1 qt/8hrs. This obviously was not true. Don Maxwell conducted the annual and pre-buy. I was told 2 cylinders had slight widening of the choke, but all else was well. Don was also told oil consumption was low which I likley led him to believe the engine was healthy. I agree the compressions alone are not concerning. However, I am reading that compression testing may not be all that helpful when viewed alone.

I fly 1400nm missions on a monthly basis. I run LOP. 28" 2400 RPM, EGT 1630, 14.5 GPH above 13,000'. Never had CHT > 370, typically 330. Usually 3 hr legs due to oil consumption. I fill oil to 6 Qt level with Phillips XC 20-50.

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I can't access the Continental website, but there is an SB for checking the running crankcase pressure.  If I recall the maximum pressure is 4"H2O or 90mph.  You'll need a replacement oil cap with a pressure connection to a water manometer or an airspeed indicator.

Clarence

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The IO550 has a few things that it is known for...

  • Lots of power that can be run hard to go fast at the cost of cylinders near the halfway point...  can you pull up data from the engine monitor?  CHTs could tell a lot about its history...
  • Plenty of power when run LOP with an eye constantly on the CHTs...  Cylinders will go the whole distance....  CHTs can be in the range of 280° to 320°F...
  • oil use isn't very much, not like the Lycoming quart per 10 hours or so...
  • Continental cylinder assemblies have a less than stellar history of valves not being concentric to their guides.  I have no experience with this issue.
  • some NA IO550s have the same challenge, so it is not specific to the TN'd version...
  • full rich, full rpm (2700), at SL can have a FF or 27.2gph, some people set the FF even higher...
  • There is a blue box to help run/set the mixture on the EGT during ROP climbs.  A white box, if you have a G1000... 

See if you can pull up any history of high climb rates, high speeds, at the cost of high CHTs... these would explain why or how the cylinders are worn.  Engine monitors and flightaware can be helpful to the sleuthwork...

As far as what a worn cylinder looks like, gets one of those dental cameras that goes down the spark plug hole, it can see the surface of the cylinder...take a look at the cross-hatch pattern and see if it is in good condition... post some pics!

The choke that was described earlier, is the part of the cylinder at the top.  It is dimensionally choked, like a cone.   It expands to be cylinder like when heated...  The part that gets traditionally the hottest is the parts closest to the exhaust valve.

The whole point of keeping the cylinders cool... is the strength of the metals...  at temps above 380°F, the rate of wear starts to increase because the metals soften as a function of temperature...

There is nothing wrong with flying in full fire breathing dragon mode.... the cost is measured in gph and hours per cylinder...

It takes a fair amount of self control to avoid the desire to fly in full fire breathing dragon Mode...  :)

There is a Rocket owner that went through a similar decision process a few years.  Check in with @aviatoreb

This is only PP thinking, not a mechanic.  All this detail is from old fuzzy memories.  Earlier today I couldn't remember the words cotter pin...

Best regards,

-a-

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Turbos kill cylinders , Mooney turbos kill cylinders faster , because the cowls are so tight....  Just a thought ,  If this was a Lycoming ,  I would try to see the burn rate keeping 5 qts in the engine , sometimes they don't burn past a certain level......  I would do some testing trying to keep 8 qts in it or even 7 qts..... You might be surprised....

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I don't know how to access engine data from the g1000. I don't believe the 2007 version has the ability to down load historical data. I could be wrong.

For argument sake lets consider multiple cylinders are bad due to poor engine management as this is most likely.

How would you approach the top end overhaul...OEM, Superior Air Parts (Millennium), Engine Components Inc. (ECI), Aircraft Cylinders of America, or recondition my own cylinders.

Does anyone have a favorite engine repair shop? 

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Just now, L. Trotter said:

I don't know how to access engine data from the g1000. I don't believe the 2007 version has the ability to down load historical data. I could be wrong.

It takes a G1000 software upgrade before it will start logging to the SD card on the top right. On the last AUX page, check to see if you're on 0401.34, which is the latest approved version for Mooneys.  You'll see files on the SD card that are named like log_170824_212532_KAUS.csv, which can then be uploaded  https://www.savvyanalysis.com/ for a graphical view of the data.

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While Mike's article was interesting I think there is a little drama to his writings, Having a Rod failure after a Cylinder R&R was more likely due to a Rod that would have failed anyway or my guess is someone tapping (or worse) the wrist pin out because they never just push out and there is noway to support the rod, thus causing flat spots on the rod bearing. He also mentions 20,000 lbs of force trying to pull the cylinder off the engine, my guess is its more like 9,500 lbs, then we get into the tensile strength of the studs, a grade 2 bolt (which I hope they are not) has tensile strength of 43,000 psi so a 5/16 bolt has and area of  0.0767 sq in resulting in around 3298 psi which is much higher than his 2500 psi needed, my dirty math is more like each stud needs to hold around 1200 psi. Anytime an engine is opened up there is the risk something will get over looked, an A&P that pays close attention to detail and has the correct tools can replace my cylinders and it would bother me a bit, well maybe the cost would....

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So who makes a decent cmi cylinder? I haven't heard good things about the factory jugs, eci had an ad so I wouldn't buy from them... Any others one should consider?

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3 hours ago, M20Doc said:

I can't access the Continental website, but there is an SB for checking the running crankcase pressure.  If I recall the maximum pressure is 4"H2O or 90mph.  You'll need a replacement oil cap with a pressure connection to a water manometer or an airspeed indicator.

Clarence

from Beech talk:  

After doing some research, my mechanic and I determined it was time to replace the crankshaft seal on the front of the engine. All of the symptoms indicated it was leaking, allowing the crankcase to become internally pressurized by incoming airflow. This pressurization was causing oil to be blown out through the breather.

We pulled the prop to begin the replacement process. Sure enough, once the prop was off, the old seal showed signs of age. The glue that goes around the outside of the seal had broken down, allowing the seal to spin in its seat. Not good. Clearly the seal was worn and was ineffective in keeping the airflow out of the crankcase.

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5 hours ago, peevee said:

So who makes a decent cmi cylinder? I haven't heard good things about the factory jugs, eci had an ad so I wouldn't buy from them... Any others one should consider?

Superior Airpart seems to make better cylinders.  Nickel carbide used by RAM hold up quite well, I've only seen one failure of the surface coating.

Clarence

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7 hours ago, RLCarter said:

While Mike's article was interesting I think there is a little drama to his writings, Having a Rod failure after a Cylinder R&R was more likely due to a Rod that would have failed anyway or my guess is someone tapping (or worse) the wrist pin out because they never just push out and there is noway to support the rod, thus causing flat spots on the rod bearing. He also mentions 20,000 lbs of force trying to pull the cylinder off the engine, my guess is its more like 9,500 lbs, then we get into the tensile strength of the studs, a grade 2 bolt (which I hope they are not) has tensile strength of 43,000 psi so a 5/16 bolt has and area of  0.0767 sq in resulting in around 3298 psi which is much higher than his 2500 psi needed, my dirty math is more like each stud needs to hold around 1200 psi. Anytime an engine is opened up there is the risk something will get over looked, an A&P that pays close attention to detail and has the correct tools can replace my cylinders and it would bother me a bit, well maybe the cost would....

Not to burst your bubble , but on the compression , power , and exhaust strokes of the engine , there is absolutely ZERO stress on the rod bolts , ZERO , I will say it again ZERO ...... Do you really think there is 10000 psi against the cap on the intake stroke ????

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Alan is right.  The studs and rod bolts are torqued to a value that is much higher than then cyclic stresses imposed on them.  So they are always in tension. If one is under torqued (or there's paint under the cylinder base nuts) the stud fails in cyclic fatigue.  Then the remaining ones fail as well but due to the overstress. 

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22 minutes ago, Alan Fox said:

Not to burst your bubble , but on the compression , power , and exhaust strokes of the engine , there is absolutely ZERO stress on the rod bolts , ZERO , I will say it again ZERO ...... Do you really think there is 10000 psi against the cap on the intake stroke ????

I never said anything about rod bolts, but since you did they are under the initial stress from the torque so it is greater than zero and goes up during the intake stroke

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All of those stresses are below the yield limit of the bolt or stud. Which means no life limit 

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2 hours ago, M20Doc said:

Superior Airpart seems to make better cylinders.  Nickel carbide used by RAM hold up quite well, I've only seen one failure of the surface coating.

Clarence

Thanks

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12 minutes ago, jetdriven said:

All of those stresses are below the yield limit of the bolt or stud. Which means no life limit 

So what your saying is there is no limit on the number of times rod bolts can be used?

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13 hours ago, L. Trotter said:

[snip]s on a monthly basis. I run LOP. 28" 2400 RPM, EGT 1630, 14.5 GPH above 13,000'. Never had CHT > 370, typically 330. Usually 3 hr legs due to oil consumption. I fill oil to 6 Qt level with Phillips XC 20-50.[/snip]

The dipstick on the Acclaim is not great.  the gradations above 6qt are very close together, and they may not correspond to what's actually in the crankcase.  I measured mine after an oil change and the 7-8qt measures were rather "off".  On the ground, a full 8 qts reads at the top of the 8, not at the line below.  Maybe the oil filter wasn't completely full.

Other comments:

Filling to 6 is insufficient. While the engine will "make" a quart of so when it sits for a week, I fill to 7 or 8.

Do you observe oil on the belly?  When my 231 needed a top, the tail tiedown ring would drip oil in the hangar.

Are the exhaust pipes coked or oily?

Figure out if you are really losing oil, and if so, where it is going.

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21 minutes ago, RLCarter said:

So what your saying is there is no limit on the number of times rod bolts can be used?

Negative , They are stress to yield , in aviation we are only allowed to use them once , In automotive , we are instructed to inspect for "necking" , and if the threads are straight , we may reuse them ....

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16 hours ago, L. Trotter said:

I realize there is scattered info on this topic but would like to update / consolidate  the topic and receive some advice.

I have a (new to me) 2007 Acclaim (1100 hrs TT) no prior engine work. Now burning 1 Qt every 1.5 hrs. Cylinder pressures low 60's throughout. Some leak heard in the breather line on nearly all cylinders. Valves look good on Bore Scope. Engine runs smooth, starts easily. Plane sat for extended periods prior to purchase. I'm told I need a complete top end.

Here is an article from Mike Busch https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2014-06_cylinder-work-be-afraid.pdf which is not very flattering in regards to top overhauls. In essence, catastrophic engine failures are more likely to occur after "proper maintenance practices"! The more cylinders replaced the higher the probability-so "Be Afraid". It seems the large bore turbo Continentals typically only make it to mid-time (about 1000 hrs). OK, I'm afraid! where do I go from here? It seems top end overhauls are routine but is this the right answer? Here is a loaded question.....What have you done when faced with this dilemma? Why?

Complete Top Overhaul ? If so, with what...OEM, Superior Air Parts (Millennium), Engine Components Inc. (ECI), Aircraft Cylinders of America, or recondition my own cylinders.  Where?

Pull the engine and have complete rebuild or factory Remanufactured?

I hate to say it, but what you're seeing is typical of the Turbo Continental 550. If you made it to 1100TT without a top end overhaul you are doing well. David Behrens at Dugosh was telling me that he has seen quite a few Acclaims that need top ends at 500 or 600 hours. But I sure wouldn't overreact and consider a complete rebuild or reman unless it was absolutely necessary.

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19 hours ago, M20Doc said:

If you're going to replace the cylinders it is cheaper to buy a complete balanced set of 6 from Continental than to buy 6 individual ones.  If you're worried about potential risk in removing them, have your shop remove and replace them one at a time.  We do it this way, but in more than thirty years I've never experience the failure that Busch warns of.

Clarence

 

That's my understanding of the situation.

For that reason, I decided to get 6 new cylinders to install when I need a top, rather than remove all 6 of my cylinders and send them in for overhaul.  This way, when the cylinders are replaced, they can be replaced one at a time.  Remove and replace and torque.  That way the engine always remains under torque, and in effect you are getting 6 single cylinder replacements rather than an all 6 at once replacement.

As far as I understand it, the main reason that continentals, turbo or not, need overhauls by or before 1k hours is that continental cylinders are crap.  Mostly the workmanship, rather than the design, and especially the valve lapping work.  They just don't seat well.  Even a highly skilled pilot who properly manages the engine, gingerly, at low temps and low power, only operating on Sunday flies to church....can't go to tbo if the valves are crap when they come new from the factory.  So the thing to do, even with new continental cylinders, is to have them overhauled by a high skill 3rd party shop before building your engine.  If that is done, then supposedly you have a much better shot at making tbo.

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