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Oil Coal on Cylinder Wall

Hi,

This is an XP-IO-360..

After the first 25 hours of run time I performed an inspection as recommended in the XP-360 operators manual. In addition to changing the oil and ignition inspection I did a borescope inspection on all cylinders.

No. 1,2 and 4 cylinders showed no anomalies and are blank and shiny, however in No. 3 cylinder I found a fair amount of discolouration on the cylinder wall (see attached pictures).

After close examination I‘m positive that this is not corrosion but seems to be oil coal. The discoloration is located on the top half/upper part of the cylinder (plenum side..).
The engine has been run according run in recommendations (e.g full rich for the first two hours, then leaned to 75° ROP for the remaining 23h) with oil consumption stabilised at around 10 hours.

Overview
SingleShot0006.jpg

Closeup top left corner
SingleShot0002.jpg

Is this something that I need to be concerned off? :confused:

Appreciate all your inputs..

Daniel
 
I have had glazed cylinders and the color was an semi-opaque, light brown. I don't see how you can get jet black, coaked oil on a cylnder wall (constant scraping by the rings prevents a build up). With glazing, the coaked oil is very thin, as it only exists inside the valleys of the cross hatch and that is why the color is so light.

My first guess would be some kind of metallurgical flaw with the barrel material. Are these the cermanil style cylinders with a coating? I would send those pic's to superior.

Larry
 
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These are „standard“ Superior Millenium cylinders, through hardened steel barrels.
Pictures are already sent to Superior, waiting for an answer..

Has anyone had a similar thing?
 
You have a very badly glazed cylinder from getting it too hot. The "black" part is normal but I dont see crosshatch. The only reasonable fix is remove cylinder, hone, new rings. Don't let it get hot! This is why I completely disagree with recommended breakin procedures.
 
RocketBob, I was going to send you an email, but I can't find your email address anywhere.

Pete

hunter (dot) navy (at) gmail DOT com
 
though a hangar neighbour and friend of mine, haven't had a 1st hand view inside the cylinders... as far as I know Touchdownzone followed the break-in procedures religiously, so not really sure what could have happened :confused:

rocketbob, all due respect, but I'm not sure it is glazing. Seen a few of those and didn't look like this.

Mahlon, if around, any take on that?
 
That really looks like rust to me. Look at the left side of the close-up. That stuff looks more brown than black there.

If this was "oil coal", I'd expect it to be uniformly around the cylinder, not localized in one area. Plus, you can see where a ring sat for a while; there's more rust in that area.

Have you cut open an oil filter yet?
 
rocketbob, all due respect, but I'm not sure it is glazing. Seen a few of those and didn't look like this.

No its glazed. The coffee color on the sides is glazed oil. The center "black" is where the piston scuffed the cylinder wall.
 
I agree with Rocketbob that this looks like glazing, but I don’t agree that the Lycoming recommended break-in procedure is not right. They caution about not letting the CHT’s to get too hot (>400*). But they recommend an agressive power setting (75%) so there is enough pressure to force the new rings outward against the cylinder walls to break them in. Unfortunately, the only way to fix a glazed cylinder is to hone it. I think you should consult a reputable engine shop before you pull a cylinder.

https://www.lycoming.com/content/hard-facts-about-engine-break

Cylinder #3, and usually #4, has a cooling challenge because of the cylinder fin casting in conjunction with our standard baffle, that prevents cooling airflow to migrate to the lower barrel fins where the rear baffle is mounted (discussed on this site in detail - see the DanH remedy). This challenge would be most evident during engine break-in when cylinder head cooling is critical because of excess piston ring friction for this period.
 
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I agree with Rocketbob that this looks like glazing, but I don’t agree that the Lycoming recommended break-in procedure is not right. They caution about not letting the CHT’s to get too hot (>400*). But they recommend an agressive power setting (75%) so there is enough pressure to force the new rings outward against the cylinder walls to break them in. Unfortunately, the only way to fix a glazed cylinder is to hone it. I think you should consult a reputable engine shop before you pull a cylinder.

https://www.lycoming.com/content/hard-facts-about-engine-break

Cylinder #3, and usually #4, has a cooling challenge because of the cylinder fin casting in conjunction with our standard baffle, that prevents cooling airflow to migrate to the lower barrel fins where the rear baffle is mounted (discussed on this site in detail - see the DanH remedy). This challenge would be most evident during engine break-in when cylinder head cooling is critical because of excess piston ring friction for this period.

The original poster indicated that he ran at 75 degrees ROP while at 75 percent power or above. 75 degrees ROP is just about the worst possible place to run an engine while at high power settings as far as cylinder temperatures are concerned!

Skylor
 
Yep, I missed that detail in the original post(75* ROP). Lycoming recommends “best power” after the initial couple hours at full rich, which would be 100-150 for this phase of break-in. If the cylinders get too hot prior to break-in due to a too lean mixture, approaching peak EGT (high temp, high pressure), you could have a problem, especially on the most stressed cylinders - #3 & #4.
 
That really looks like rust to me. Look at the left side of the close-up. That stuff looks more brown than black there.

If this was "oil coal", I'd expect it to be uniformly around the cylinder, not localized in one area. Plus, you can see where a ring sat for a while; there's more rust in that area.

Have you cut open an oil filter yet?

The other clue that points away from glazing is the affected area is on top, which is the coolest part of the barrel. I have only seen glazing on the sides or bottom of the barrel. It is also odd to have zero glazing on the other three jugs. If one was that bad, I would expect at least light glazing on another jug or two.

It looked black to me, but the edge shaping does resemble corrosion.

Larry
 
Thanks for all replies and opinions.

I agree its hard from the blurry pictures to see whether its corrosion or baked oil.
Before first engine start I did a borescope inspection as well and found all cylinder corrosion free (might have missed that particular spot though:().

I did cut open the oil filter, did not find anything unusual.

Running the engine 75° ROP is according Superior Airparts XP-360 operators manual for break-in. I checked my engine monitor and found cylinder #1 and #3 to run about 10°F cooler than #2 and #4, with #3 often showing the coolest temperature (I did the baffle mod suggested by DeeCee and DanH).
During the first couple of hours I did not see CHT above 420°f during climb out and during cruise the CHT stabilised in the 380°F region.

Tomorrow I will try to scrape the cylinder wall with a small tool I made out of some scrap aluminium to find out more. Wiil keep you informed..
 
75 ROP vs 150 ROP is unlikely to be an issue here. Concern for operation in the 50~75 ROP region is based on being near/at the detonation limit, assuming CHT is near 475, hot intake air, poor fuel, etc.

That scope photo is too fuzzy to tell much of anything.
 
Is this black area on the bottom (ie. closest to the ground) of the cylinder? The edges of this look like corrosion to me. The pattern looks like what you'd get if there was some moisture collected in the bottom of the cylinder while it was stationary for a while.

You can even see two lines that run circumferentially out of the affected region. That immediately says "rings" to me, suggesting that's where the cylinder was sitting. Moisture started corrosion in the lowest part of the cylinder, and moisture wicked up along the rings starting corrosion along those lines around the circumference.

How long did the engine sit before first start? And where was it stored?
 
the blackened sector is furthest away from the ground, so it's the top section.

The engine has been sitting for a while, but was well conserved and looked after.

In the mean time I found some pictures that I took before first engine start. Although not the same detail, I can clearly see that there was no corrosion present then.

SingleShot0038.jpg

SingleShot0039.jpg

SingleShot0040.jpg

SingleShot0041.jpg

SingleShot0042.jpg

SingleShot0043.jpg

These shots are from the 18th May 2020. I have flown 25h since then.
I think its very unlikely that this is corrosion on #3.. :(
 
anything else?

Daniel - do you have any other issues with the cylinder besides the borescope concerns? EGTs or CHTs running differently? Might also do a compression check to see if the rings are leaking.

What kind of oil? Are you running 100LL or UL91 or mogas?

Anything strange with the spark plugs?
 
Ground Run

Did this engine see much ground run time and high-power run ups without the cowling before it was flown?
 
the blackened sector is furthest away from the ground, so it's the top section.
...
The engine has been sitting for a while, but was well conserved and looked after.
...
These shots are from the 18th May 2020. I have flown 25h since then.
I think its very unlikely that this is corrosion on #3.. :(
Hmm... Well, the only other thought i'd have then is condensation... Which may form at the top first. But I admit i'm reaching here. I can't get my mind to stop seeing the witness marks where the rings sat.

Could that cylinder have been "less well" preserved? Could there have been moisture in there before it was preserved, and the prop not moved while it was sitting?

Are you 100% sure of the orientation of the cylinder, I know I have trouble tracking which is "up" when i'm using my borescope.

Could this be residue from any preserving oil that was fogged into the cylinder while it was parked?

Trying the buckshot approach here... Hopefully something triggers some further ideas/suggestions...
 
EGT's and CHT's run pretty close together..
Using 100LL and PHILLIPS 66 X/C 20W50..
Spark plugs indicate mixture on the rich side..
Did not perform a compression check so far..

The engine did not see any high power runs with cowling removed.
For certification I had to do a static thrust check on ground, but this was done with cowling on and CHT in view..

Today the cylinders were examined again with a high resolution/contrast borescope by a local A&P mechanic and an experienced forum member.

The bad news is they both agree that this is corrosion :(
The not so bad news, they both state its safe to fly, and check again in a few hours :cool:

Personally I find it hard to believe that a cylinder goes from shiny to corrosion in 3 months time while flying 25h.. :confused:

On the other hand, there is also a chance that I loose weight. Its highly unlikely, but.. :D
 
engine dryer

Might want to think about an engine dryer - I use the Black Max. I did check the humidity reduction and it was pretty good. No idea really if it will save my engine from corrosion, but for the price, it's pretty cheap insurance. They have it in 220v as well as 110v. https://flyingsafer.com/2065

2065.jpg


Most aircraft in my hangar have a battery charger, I have an engine dryer. Reminds me of the F-4 GPUs. I hook it up right after every flight, even if it's just for a lunch break. Check back in 20 years to see if it was worth it. :)
 
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Question about the dryer

Might want to think about an engine dryer - I use the Black Max. I did check the humidity reduction and it was pretty good. No idea really if it will save my engine from corrosion, but for the price, it's pretty cheap insurance. They have it in 220v as well as 110v. https://flyingsafer.com/2065

2065.jpg


Most aircraft in my hangar have a battery charger, I have an engine dryer. Reminds me of the F-4 GPUs. I hook it up right after every flight, even if it's just for a lunch break. Check back in 20 years to see if it was worth it. :)

The dryer sounds interesting but on my installation, I believe that it is typical, the end of the crankcase breather is coped and fitted close to the engine exhaust header. Did you install the breather just exiting parallel to the engine exhaust to allow insertion of the dryer connection?
 
breather tube

The dryer sounds interesting but on my installation, I believe that it is typical, the end of the crankcase breather is coped and fitted close to the engine exhaust header. Did you install the breather just exiting parallel to the engine exhaust to allow insertion of the dryer connection?
I have my breather just above the exhaust pipe so it will drip onto the exhaust, and I have space to put the tube in it. The end is perpendicular to the exhaust. I could have made it a bit easier to install, and might change it in the future. Some put it in the filler cap, replacing it with a 3d printed cap with a hole. The problem with that is you need to find a good place to leave your dipstick.
 
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