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Cylinder #3 scoring, normal wear or something else? Dental cam pics.

designerX

Well Known Member
Running a compression check on an XIO-320 D1A (200 hours since rebuild) with .010 overbore steel cylinders shows that #3 compression is down to 68/80 cold and 70/80 hot (last year it read 74/80 cold.)

During compression check air can be heard in the case by opening the oil filler, I assume is blowing by the rings on #3.

Armed with a newly acquired eBay dental camera marks can be seen at the 12 o'clock portion of this cylinder (within the nice hone/hatch marks.)



The spark plug was generally clean but did have a couple very small kernels of lead. The wear appears to be barely deeper than the cylinder cross hatching but is hard (impossible) to discern w/the magnified images.

Here is an image of the 6 o'clock position of cylinder #3.

 
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Something's not right there, I would pull that cylinder and have a looksee. In the first pic that much wear at 200 hours is not right.
 
I agree with Bob, that cylinder needs to come off. My speculation is that something is stuck in a ring gap or something like that. It almost looks like you have a concentration of deep vertical scratches caused by something going up and down with the ring and causing the gouge. The second pic shows a typical example. In the first picture, it looks like the offending defect is rotating slightly, making me think it is the ring itself or something lodged or stuck to the ring. Either way, that cylinder is likely going to need a re-bore.

Larry
 
I don't know about the cylinder, but your camera images are excellent! Care to share the e-bay link?
 
The dental camera has lots of magnification. Look at size of crosshatch. Also, LED lights may give reflections that make it look worse.
 
Stan;
That's some good photography.
Sometimes the pic makes things look worse than they are.
Did you try to feel the scratches in the bottom with something like a dental pick? you can feel very small scratches.
On the other hand, you have measurable loss of compression. It's still in the 'safe to fly' reading, but I agree with Bob and Larry. If you are tool handy you can save your self a lot of time, money and worry.
 
I had some of the ECI cylinders that were part of the recall. When we took them off we found a similar pattern to what you are seeing and it was caused by the coating on the rings that had delaminated. Apparently this was also and issue that ECI had for a short time period. I has since been corrected. I wonder if this could be your issue?
 
The dental cams can make minor (read normal) things look awful in a cylinder.

With that said, your photo #1 is showing something that looks unusual. If I had that wear pattern (ie., discernible and unique to only that cylinder) and leakage past the rings, I'd pull the cylinder and take a look.

Dan
 
Stan,

I have seen this wear pattern many times over the years, it?s can be caused by rapid expansion of the piston caused by leaning too quickly, rapid cooling of the cylinder by reducing power quickly or a cooling system that is not functioning well. The scratches are in the thrust plane only. I would suggest to you that this cylinder is not going to heal itself it is only going to get worse; it should be removed and repaired.
Once it is removed you will probably find the thrust face of the piston scratched and the rings as well. If you measure the piston to cylinder wall clearance and ring to ring land clearances and they are with in tolerances the piston can probably be reused. If it is not in spec it should be replaced.
If the scratches can be removed by light honing (Not de glazing), replacing the rings and running-in the cylinder will bring back the lost compression.
 
Thanks for the helpful replies

Thank you all for your replies! I plan to remove this cylinder and go from there.

Tom, I checked for ECi parts.. the cylinders are Lycoming and the pistons are Superior.

Excellent Bobby, I was hoping someone out there had seen this same wear pattern. I have cut the throttle at altitude and tried gliding... I had read through the years that our tightly cowled RVs were generally immune to the shock cool? When you say leaning too quickly.. do you mean too aggressively (over leaning?)

For those inquiring about the dental camera here is a link to a newer version of the one purchased (and by the same seller) http://r.ebay.com/7IkF5Q . Note: the head of the camera housing must be cut which is easy and documented somewhere in the Forum.
 
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He means leaning at a rate that heats the piston faster than the cylinder, thus tight jug. You can figure around .002 in. per 100 deg F expansion on a cylinder and .004 in. per 100 deg F on a piston. Pretty close.
 
LOP Ops?

For the engine guru's out there: How does this relate to the "Big Pull" advocated by the LOP operators? Wouldn't that be classed as "rapid leaning?"

I have no experience in LOP ops, as I have a carbureted O-360 with two Slick mags. I lean slowly until the engine loses power, then richen up just a bit.

Thanks!
 
From ECI Report

The engine Coughed, and a brief flame was observed coming from the exhaust. However, an engine
analyzer was being used, and no detonation was observed on the scope.
I have placed increasing reliance on the data delivered by the engine monitor
and left tried and true common sense behind in operating my engine.
Although I have reverted my procedures back to what has worked well for me for 30 plus years, I still do the BMP to LOP as soon as I establish cruise at less than 65% power.
It's interesting to hear this information from a Titan Expert and I can't wait to see what the self proclaimed gurus have to say about it.
 
Not over leaning, but how rapidly leaning is done in time. Usually this causes the aluminum piston to expand faster than the steel air cooled barrel around it, this decreases clearances. And can cause scuffing from the extra friction. This can cause a permanent decrease in size of the piston in the thrust plane.
Rapid enriching or large reductions in power suddenly, can cause the reverse to happen sudden cooling of the barrel which has a lot of cooling air flow causes it to shrink over the still hot piston reducing clearances causing the same kind o f problem.
See our report about rapid leaning for more information. http://www.eci.aero/pdf/93-6-7.pdf
 
This explanation fits the reason only cylinder #3 was affected

I have seen this wear pattern many times over the years, it’s can be caused by rapid expansion of the piston caused by leaning too quickly, rapid cooling of the cylinder by reducing power quickly or a cooling system that is not functioning well. The scratches are in the thrust plane only. I would suggest to you that this cylinder is not going to heal itself it is only going to get worse; it should be removed and repaired.


Piston/cylinder temperature differential could also help explain why only the 12 o'clock cylinder portion of #3 has this wear pattern on my -4... the primary air intake is right behind/over this cylinder.

As the ECi article mentions.. yes, I have a fuel flow meter and am familiar enough w/my bird to know what gph rate should be at various power settings and have used it to lean. I will be slowing down and much more reserved on my leaning procedures... a few gallons of 100LL is much cheaper than a cylinder/piston and the time to replace it. Thanks everyone!
 
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I think there is more to it......

I think that in addition to the rate of leaning, you have to consider the level of leaning itself.

If you are running 100* rich of peak, and lean to 100* lean of peak I do not see how a rapid leaning can cause the kind of damage listed in the above document. In face, it would seem that the quicker you lean the better.

Now, if you are at 100* rich, and lean rapidly to peak, or only a few degrees away from peak, that will most likely cause the problem described.

Or, if you are at 300* rich, and rapidly go to 100* lean-----

What is the overall temp change, and what rate is it done at are what I expect are the determining factors.

Big question seems to be how to reliably hit the correct target on the lean side without the temp spike that is going to cause damage.
 
I am not sure that I buy the rapid leaning argument. I also have seen scuffing caused by too tight of piston to wall clearance and I don't believe that this looks the same. I see discrete vertical gouges, which lead me to the conclusion that a foreign object or failed ring is causing scratches. Not exactly sure what it is, but in my opinion, something is causing relatively deep scratches in a pattern that are moving radially.

The problem should become obvious once you pull the cylinder. Please post picture of the cylinder bore, piston and rings once you pull it so that we all can learn from your experience. If possible, try to keep the rings from turning when you pull the jug. This way you can examine the piston and ring in the same vertical plane as the wear areas on the bore.

Larry
 
Interesting! Will be looking for the results after it's pulled.

I flew a C-177 for ten years without any engine monitering at all other than the sputter of over lean and then backing off to make it run smoother. Had no idea about leaning other than it make the engine stronger and burned less fuel. Having all this modern gizmo technology is making me worry a lot about what I never knew before! :eek:
 
If you are running 100* rich of peak, and lean to 100* lean of peak I do not see how a rapid leaning can cause the kind of damage listed in the above document. In face, it would seem that the quicker you lean the better.Now, if you are at 100* rich, and lean rapidly to peak, or only a few degrees away from peak, that will most likely cause the problem described.

Amen!
Anyone who has played with the mixture knob and is capable of LOP knows that temps go DOWN when you lean past peak. Common sense says to lean rapidly from ROP to LOP to eliminate/minimize the time with peak temps. Me thinks John Deakin and Mike Busch have rolled their eyes a few times over claims of cylinder damage from too rapid leaning. Fits right in with claims of burnt valves from "over-leaning". Funny how no one claims cylinder damage due to rapid advancement of the throttle during takeoff. Time to abandon these myths.
 
If your pistons have a oil scraper ring on the bottom of the piston skirt, check which direction the large chamfer is oriented. I had to rebuild my O235 because the chamfer on that ring was installed incorrectly causing dry cylinders. I know the Lycoming manual instructs the rings to be one way for the O235 and the other way for the O320.
 
Amen!

Anyone who has played with the mixture knob and is capable of LOP knows that temps go DOWN when you lean past peak. Common sense says to lean rapidly from ROP to LOP to eliminate/minimize the time with peak temps. Me thinks John Deakin and Mike Busch have rolled their eyes a few times over claims of cylinder damage from too rapid leaning. Fits right in with claims of burnt valves from "over-leaning". Funny how no one claims cylinder damage due to rapid advancement of the throttle during takeoff. Time to abandon these myths.
Not only that, but wouldn't ALL the cylinders exhibit the same symptoms if leaning were the cause?
 
forensics

Take a look at how high the scratches go, either on cam or when you get it apart. You might be able to determine which ring the damage is attributable to. For example, if it only extends up as high as the oil ring travels, that tells you it is probably the oil ring.

If it stops well below the top of the oil ring travel, look for something up with the piston.
 
Not only that, but wouldn't ALL the cylinders exhibit the same symptoms if leaning were the cause?

I was wondering the exact same thing, Noah. Unless the cooling of this particular cylinder makes it unique. ????????????
 
For those inquiring about the dental camera here is a link to a newer version of the one purchased (and by the same seller) http://r.ebay.com/7IkF5Q . Note: the head of the camera housing must be cut which is easy and documented somewhere in the Forum.

Counting mine just now, 17 sales in 24 hours, after only one on April 24th. That vendor owes you a commission! :)
 
Not only that, but wouldn't ALL the cylinders exhibit the same symptoms if leaning were the cause?

I was wondering the exact same thing, Noah. Unless the cooling of this particular cylinder makes it unique. ????????????

I believe Titan Expert was addressing the issue of temperature differential.. not just leaning. Yes the air intake is behind cylinder #3 not at the bottom of the cowl like many RVs. The engine monitor displays very similar CHT for all 4 cylinders but if there were a case of (overly?) aggressive leaning or shock rich/cooling most likely this cylinder would be affected.
 
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Counting mine just now, 17 sales in 24 hours, after only one on April 24th. That vendor owes you a commission! :)

Hah. The unit pictured looks exactly the same but a 4 mp image will make every minor hone mark that much more frightening. :)
 
Shock cooling and thrust side of cylinder barrels

I, too, have had reservations about shock cooling theory, given that the thermal stresses on a cold engine at start-up must be many times greater than leaning under power. On the other hand, an engine under power is producing much more heat with much more internal pressure. So I don't know what to think, but I move the red levers slowly after giving the engines time to catch their breath after a long climb, for tradition's sake if nothing else. As an aside, the man who taught me to fly told me a hard side slip on a winter's day in an airplane with an OX-5 with short stacks was a sure recipe for warped exhaust valves.

Lovely pictures for a $30 camera. I must have one. Does anyone have a link to the camera modification page?

This hasn't been mentioned yet. The thrust side of the cylinder barrel is 12 o'clock for cylinders 1 and 3 on a four cylinder Lycoming, and 6 o'clock for cylinders 2 and 4. The barrel scoring at 12 o'clock suggests something happening as a consequence of that thrust. I hope the OP posts pictures of the tear down.
 
I have seen this wear pattern many times over the years, it?s can be caused by rapid expansion of the piston caused by leaning too quickly, rapid cooling of the cylinder by reducing power quickly or a cooling system that is not functioning well.

Old Wives Tale alert. From folk who have done the research on this and measured this stuff (STC work on cooling mods) I am pretty confident in saying that the other causes for scuffing are more likely than leaning quickly. That claim is simply and scientifically not true nor possible.

Parade Rest.
 
David, what do you consider are the "other more likely" causes of the scuffing often(or not often?) seen on the piston skirts?
 
One other possibility that could cause this type of damage is the cam beginning to fail or lifter spalling. Did you see an increase of metal in the last filter change? If you remove this cylinder make sure you inspect the cam and lifters for damage.
 
David, what do you consider are the "other more likely" causes of the scuffing often(or not often?) seen on the piston skirts?

I am not answering for David here, his view is awaited. But . . .

We only have a part of the data we need here. The piston needs to be removed and inspected visually. Was there smearing of the skirt? Were ring butt gaps large enough? Was this a new piston or was the old one cleaned? At one time glass bead cleaning was approved. YIKES!, Never on my engine, I spent $300K (OPM) having my manufacturing people relearn how to clean parts after beading. (long story not for here)

Metal transfer would indicate higher piston temps. Typically, piston to cylinder clearances are monstrous compared to automotive and liquid cooled engines, even marine and racing, due to potential seizure. Seizure from a cooking hot engine flying into a heavy rain!!, that will close the clearances much faster, and to a smaller number than throttle off or leaning procedure.

Since this engine is 200 hr old, and over bored, I would consider cleanliness of the build, roughness of the suspect cylinder, build clearances of piston/bore, piston ring gaps, advanced ignition timing to start the process.

It is hard enough, sometimes, standing and looking at all the parts with all the information to determine a cause, and here we only have a small part of the story.

Lets see what the teardown shows.
 
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For those of you who (like me) purchased the aforementioned dental camera and do not have accommodations to load the program to your Mac from a CD, how did you get the software? Thanks
 
No software

On Macs, just use photo booth and plug the camera into a USB,
no need to load software at least not on mine.
 
update

It's been a long time since I started this thread and figured it was a good time for an update.

After consulting with my trusty mechanic he recommended to continue flying the airplane (while paying attention to #3 cht/egt and be on the lookout for any oil consumption.)

He put little merit in these photos and made his decision based on the compression and the fact that I have practically no oil consumption (1 quart every 12+ hours or so.. and that's with turning her upside down on occasion.)

After flying for 35+ hours my oil consumption is the same, filter and oil are good AND the compression on that cylinder read 74/80! With excellent leak down and zero signs of air escaping past the ring!

As you can imagine I'm very pleased, especially since I was braced for removing that cylinder. After all this I'm a bit hesitant to put much weight into the dental cam images... I think the lighting and magnification makes for an greatly exaggerated surface.

I don't know how a cylinder tests 70 and then tests again 6 months later at 74... but that's exactly what happened in this case. I used the same compression gauge and even the same helper (thanks Ron!) And thanks to all that helped contribute, speculate and share their cylinder experiences.
 
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It would be recommended to take regular oil samples for analysis to see if the scuffing is progressing. Aluminum would be elevated. Just in case it does not heal itself.
 
Thanks for the update

Stan, glad to see you are not having any major issues of concern.
I think you did well in following the advice of your trusty mechanic.

The highly magnified and thus exaggerated images of dental cameras used for
cylinder and valve inspections leads to much uhhh and ahhh but rarely leads to revealing a potential problem.
I do believe bore scopes, even the cheap ones have their place when used in conjunction with
other diagnostic tools and findings such as poor compression checks or
unusual cylinder temps.
Simply poking around inside a cylinder and looking at a magnified buildup of carbon deposits is enough to scare the "puhjeebers" out of most novice
engine "experts".
 
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