Millennium cylinder wall "washboarding"

ColinD

ColinD

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Jacques de Gatineau
I'm witnessing some really nasty wear patterns in a couple of Superior Millennium cylinders on the Lycoming O-235-L2C in my airplane. I installed one cylinder last September (approx. 180 hours ago) and another a couple weeks ago (approx. 25 hours runtime.) The two Millennium cylinders in questions are installed up front in positions 1 & 2. In both instances, I set the ring end gaps in accordance with the Superior L04-01 service letter and followed Lycoming's 1427C break-in service instruction with a few deviations (For example: first flight was truncated from 2 hours down to 90 minutes due to the airplane's limited fuel capacity.) I used Phillips X/C 20W50 from the onset. The rings aren't installed upside-down.

The airplane's engine instrumentation is extremely spartan, with only oil temperature and pressure. I have no way of monitoring cylinder head temps, so I have been avoiding steep climbs and prolonged WOT operation but always keep the power above 65% (and preferably 75%) until short final. I've avoided pattern work, continued with cross country flights waiting for the oil consumption to stabilize, but it's never gotten down to a level I'd consider acceptable. Looking at the following borescope images, I can see why.

After installing the first Millennium cylinder, oil consumption never exceeded 5 hours/qt, and now it's down to 3.5-4 hours/qt. Compressions measured at TDC are 75/80 or better on both cylinders, but I suspect rings' seal radically changes every 1/16 inch of stroke as the piston travels up or down the bore. Lots of oil pooling in the top end, lots of blowby out the breather.

Wondering if anyone here has encountered this 'washboarding' wear pattern, and if they were able to determine a cause. I think I heard Mike Busch briefly mention a bad batch of Superior cylinders on an older episode of the 'Ask the A&Ps' podcast, and I'm finding a few mentions of this type of wear on other forums and older Reddit posts. My first instinct is always to blame myself, I'm just not seeing where I screwed up. I've built a bunch of engines in my life and never had trouble like this. Is it really bad metallurgy or machining practices?

An interesting comparison: Being a cheapskate, I overhauled the rear cylinders on this same engine by restoring the crosshatch with a ball hone, lapping the valves, and installing new-old-stock Superior rings from an eBay parts liquidator. They were the same part numbers as the rings included in the new Millennium cylinder kit. The refreshed rear cylinders have no unusual wear, with the same ring gapping and break-in protocol.

The gruesome images (taken today, disregard the timestamps):

IMG_0003.JPG
IMG_0001.JPG
IMG_0009.JPG
IMG_0019.JPG
IMG_0005.JPG
 
I hadn't borescoped the 180-hour one in a while, but I had the cowling off and the borescope handy to inspect the recently-replaced cylinder so I decided to take a look in the other three holes.
 
ColinD said:
I used Phillips X/C 20W50 from the onset.
Click to expand...
What made you use the 20W50 vs the recommended 100% mineral oil in both the Superior and Lycoming break-in bulletins?
Do you run MOGAS?
At 180 and 25 hours I would expect to still see some of the original cross-hatch. So my initial guess would excessive scuffing which is the loss of the oil film between the rings and cylinder wall. And your consumption levels seem to point to that as well.
Regardless, if you think it could be cylinder related, simply contact Superior for some input.
 
Fair enough. I have heard a good deal of first hand testimony from mechanics and engine builders advocating for XC 20W50 during break-in, and Phillips advertises it as being suitable for break-in. My understanding is that the oil with the Camguard-like anti-scuff additives are to be avoided (like Victory 20W50.)

I pulled the plugs and borescoped after the first run and the wear pattern was already somewhat visible, albeit more faint. No MOGAS during the initial break-in flights.
 
Phillips XC20-50 is mineral oil, but with ashless dispersent added. It breaks engines in just fine.

Fretting. Have you asked Superior?
 
Is that a 360 degree pattern? Your gaps may well have been fine, but what about ring land back spacing and ring land vertical clearance? If the rings were out of spec from the factory or the piston ring lands were, then I could imagine this pattern, though never laid hands on it in person. Potential ring flutter. I’m no aviation engine builder however, but been living & breathing engines over 45 years and that’s my educated guess. The only way to tell is to dismantle and measure your existing equipment. If it’s indeed flutter, you might see some erosion on the piston-to-ring contact surfaces?
 
Google suggests something called fuel washing. A flooded engine on initial start or during early break in washes the oil coating from the cylinder walls, damaging the surface.
 
455 Bravo Uniform said:
Is that a 360 degree pattern? Your gaps may well have been fine, but what about ring land back spacing and ring land vertical clearance? If the rings were out of spec from the factory or the piston ring lands were, then I could imagine this pattern, though never laid hands on it in person.
Click to expand...

Yeah, the wear pattern goes 360°around the bore. I didn't make an attempt to measure the vertical clearance of the rings as they were installed between the ring lands, but it didn't strike me as abnormally sloppy when I assembled it.

I'll reach out to Superior after the weekend and see if they have any ideas.

Someone on the VAF forum reported similar wear on ECI cylinders. There's some interesting discussion about rapid leaning in that thread - something, by their definition, I'm certainly guilty of. (I don't fly this plane high enough to lean in the climb, and don't spend several minutes gradually leaning to the onset of roughness.)
 
Interesting discussion on VAF. A pic of those rings looked like their outside edges got rounded. I’d say in that case, they possibly “rocked” within the ring land and caused the rippling in the cyl. Because the width of the land or thickness of rings was off.

The discussion on leaning rate and resultant temperature impacts on metals sounded weird to me. I’d think we would see more of this if it was operator error (dang pilots)

I wonder if the number of ridges in your cyl match the number of cooling fins??? If that were the case, maybe temperature or cyl metallurgy are the root cause and not flutter or ring rocking?
 
Yeah, I was suspicious of the rapid leaning theory for the same reason. You'd think every flight school airplane would exhibit this type of wear if that were truly the culprit.

This plane doesn't get flown in the winter (open cockpit,) so I'll tear the cylinders off and inspect before too much longer.
 
ColinD said:
I have heard a good deal of first hand testimony from mechanics and engine builders advocating for XC 20W50 during break-in, and Phillips advertises it as being suitable for break-in.
Click to expand...
Just a note, warranty is warranty and if an alternate break-in method is used it can become an easy decline for the OEM. Something to keep in mind.
 
Talk to tech support at Superior. They may be able to help; the lack of mineral oil break in may or may not hinder a warranty claim (cylinders, not labor).

In general, turbos can be broken in if permitted by manufacturer with a fully non-synthetic oil (Phillips 20W/50 XC) but I think most are recommending a mineral oil, whether a Shell straight weight or a multi-viscosity like 20W/50 Type M from Phillips, for NA engines.

Doubt it's leaning, fuel washing, or magic pixy fairy dust.
 
Presume these are later millenniums and not early type with a steel Liner
that was inserted into the aluminum fin pack?

Seen this condition on a O-320 E2D in a 172 Fish Spotter. Most likely were
Lycoming jugs at that time. Never a definitive culprit but we many hours at
low power could have been a factor.
 
I'm not familiar with the early style Millennium cylinders, but mine are the ones that are currently on the market. Funny you mention the fish spotting plane, I just came across your reply about that airplane in this thread regarding the same wear pattern. Also came across this discussion on Reddit and this one on supercub.org (I joined the forum to view the attachments, which are the screenshots from a Facebook group reposted below.)

IMG_5194.jpegIMG_5195.jpeg

Kind of looks like it's becoming a known issue, or maybe a bunch of us are just bad at cylinder break-in. I'll call Superior.
 
ColinD said:
Yeah, I was suspicious of the rapid leaning theory for the same reason. You'd think every flight school airplane would exhibit this type of wear if that were truly the culprit.
Click to expand...
They teach students to lean? :rofl:

I'm skeptical of the rapid leaning hypothesis as well, but it is a good reminder for me to slow down just the same. It's not like I'm doing the big mixture pull to run LOP in my 140...
 
That is a problem with tooling or the walls being too thin, almost has to be. Having an AD in the oil did not cause that and "leaning too fast" is just crazy talk.
 
Dixiebluesky said:
That is a problem with tooling or the walls being too thin, almost has to be. Having an AD in the oil did not cause that and "leaning too fast" is just crazy talk.
Click to expand...
Walls too thin? What does that even mean? OP will get best response from Superior. Not net speculation.
 
O
Steamflyer said:
Walls too thin? What does that even mean? OP will get best response from Superior. Not net speculation.
Click to expand...
Well sure, but speculating and pondering on these things is part of the fun of internet boards. The cylinder walls are not going to be too thin in this instance. I have just seen sort of similar looking patterns in an engine when liners were pushed just a bit too far. Not nice symmetrical rings all around like this, it was mostly down one side from what I recall but that was years ago. I wish I had pictures of some of that stuff from back in the day.

But lines aside something is extremely wrong here. They look like they have 2000 hours at 200. Heavy vertical striations no cross hatch at all and the top picture looks like it has a chunk missing. While the honed cylinders look good. It would be interesting to see a couple pics of them if they get taken off. It is almost as if the metal looks soft.
 
Dixiebluesky said:
Well sure, but speculating and pondering on these things is part of the fun of internet boards. The cylinder walls are not going to be too thin in this instance. I have just seen sort of similar looking patterns in an engine when liners were pushed just a bit too far. Not nice symmetrical rings all around like this, it was mostly down one side from what I recall but that was years ago. I wish I had pictures of some of that stuff from back in the day.

But lines aside something is extremely wrong here. They look like they have 2000 hours at 200. Heavy vertical striations no cross hatch at all and the top picture looks like it has a chunk missing. While the honed cylinders look good. It would be interesting to see a couple pics of them if they get taken off. It is almost as if the metal looks soft.
Click to expand...
While speculation is perhaps fun, in a maintenance section, feels like it should trend more towards solid information. But hey, that's perhaps just me.

The aircraft cylinders we use in Lycoming and Continental air cooler aircraft engines consist of machined steel barrels mated via a threaded-and-friction connection to a cast aluminum head. There is no pressed in liner like in many cars which have aluminum blocks. The manufacturing process for the barrels (the part in question here) is highly automated and rife with multiple very close tolerance quality inspection/control steps. From the raw material through the finished and honed product.

OP was seeking guidance; in this case the correct guidance is to call Superior tech support if OP feels like this is abnormal and warrants a warranty claim. They are very good about warranting their products. As you note, this is not the first time washboarding has been observed, but this is early.
 
New pistons and wrist pins in addition to the new rings and cylinders?

This almost looks like the wear you'd get from - grace requested for the odd phrasing - "chattering". What you'd see on a tire that is out of alignment. I have no idea how that would come into play. What a puzzle. What mechanical forces can give you wear that is perpendicular to the direction of motion of the piston?

Besides the suggestion to ask Superior, I've got nothing to offer but curiosity and best wishes.

Edit: Just re read more carefully. This is an interesting idea.

455 Bravo Uniform said:
Potential ring flutter
Click to expand...

Extra Edit:
The folks who I bought my plane from did some "top end work". They put in new rings, not new pistons, and supposedly reworked the cylinders. Since then I've done a complete top end. Point being that I getting the idea that you need all new / a "fresh start" of pistons, rings, and wrist pins in a new/overhauled cylinder or things just aren't going to work.
 
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Yeah, it was the whole shebang - cylinder, piston, and rings as supplied by Superior. (EDIT: Reused the original wrist pins; Millennium cylinders do not include a wrist pin.)

Left a voice mail with Superior customer service today. Hopefully we can reach a conclusion, I'll keep this thread updated.
 
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Just got off the phone with the Superior customer service rep, and he's shipping out a pair of replacement cylinders. He was familiar with the issue, and said they suspect it has to do with their honing process. I asked if it seemed to affect a certain range of serial numbers and he said it's been appearing sporadically since about 2021.

Hope the next batch hold up!
 
ColinD said:
Just got off the phone with the Superior customer service rep, and he's shipping out a pair of replacement cylinders. He was familiar with the issue, and said they suspect it has to do with their honing process. I asked if it seemed to affect a certain range of serial numbers and he said it's been appearing sporadically since about 2021.

Hope the next batch hold up!
Click to expand...
I mean, having to change cylinders sucks, but shipping you new ones is pretty good.
 
Totally. I'm satisfied with the resolution as long as the replacements don't exhibit the same issue. This plane is about as simple to work on as they come, a cylinder swap isn't particularly arduous work.
 
Cool beans!!

I would love to understand what part of the honing process would cause such an outcome. It’s very interesting from a scientific and engineering standpoint. I’ll buy you beers or cigars or sodas if you can get more detail out of them.
 
ColinD said:
Just got off the phone with the Superior customer service rep, and he's shipping out a pair of replacement cylinders. He was familiar with the issue, and said they suspect it has to do with their honing process. I asked if it seemed to affect a certain range of serial numbers and he said it's been appearing sporadically since about 2021.

Hope the next batch hold up!
Click to expand...

That’s a bit scary, seeing that I bought 4 new Superior cylinders for my recent overhaul.

Is it limited to any particular models?
 
Not sure. I don't necessarily think the guy was being evasive, but he didn't volunteer a lot of details. The replacement cylinders were offered right off the bat without showing borescope images, so I get the impression they were already well aware of the issue.
 
I had a Superior IO-400 installed when Superior recalled them. I went to their shop and saw it torn down, along with a few others. I believe I was the first customer to be told they were condemning all IO-400s and IO-382s and buying them back, including freight costs. They were more than fair and the settlement was quick. They sold me back any bolt-on components like Emags and API injection at 50 cents on the dollar. I asked what their stockholders thought of the deal. The answer? No stockholders. It’s a privately held company owned by a wealthy Chinese businessman, and he directed the buyback. That gentleman is a stand-up guy. He took a big hit to do right by his customers.
 
ColinD said:
Fair enough. I have heard a good deal of first hand testimony from mechanics and engine builders advocating for XC 20W50 during break-in, and Phillips advertises it as being suitable for break-in. My understanding is that the oil with the Camguard-like anti-scuff additives are to be avoided (like Victory 20W50.)

I pulled the plugs and borescoped after the first run and the wear pattern was already somewhat visible, albeit more faint. No MOGAS during the initial break-in flights.
Click to expand...
Oh no.

PRIOR TO START-UP:


• Engine should be filled, according to the operator’s manual, with 100% mineral oil (specific grade
depending on ambient temperature).
 
Timbeck2 said:
Wonder if that model has tapered cylinders and they didn’t hone it with a taper
Click to expand...
Their ring gap information indicates checking gaps at two locations in bore, suggesting they are choked cylinders. Usually when these things go sideways, it's not dimensional, it's material and/or material treatment.
 
They were definitely choked. I measured the ring end gaps at the prescribed depths, and they were tighter near the top of the stroke than upon initial insertion.
 
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