My cylinders are currently removed for overhaul due to a broken ring.
My oil temps had been running higher than normal all summer. I presumed it was due to warm weather operations. Looks more likely due to blow by.
My oil consumption went from a quart every 5 hours or so to a quart every hour or two; this change in oil consumption was acute between one flight and the next.
Compression test showed 75+ all around. Engine was still producing good power. It had an occasional hickup transient loss of power. Strangely, when I blew into the air-oil separator I could hear an air leak from somewhere near the front of the motor, and a quarter turn of the prop would make it come and go. I still don't understand what was causing this; it wouldn't replicate when I got the plane to my mechanic.
I decided to investigate. We found a broken ring on cylinder #3. It's spark plugs were slightly oily. Engine is a Titan X-340 with approx 350 TTSN
Advanced timing can not only give high CHT, but very high piston temps causing skirt scuffing. That aluminum transfer to the walls will stick rings and yield a lot of blow-by. High probability that broken rings were a result of this and nothing to do with the cylinders, new or old.
I might guess your engine does not have oil jets under the pistons?
My engine lacks oil squirters. Not sure if that is related to the ring breaking. Just citing as a data point. My CHT's never go above 400; they typically max out in the 390 range during climbs. Standard mags timed 25 degrees.
Wonder how effectively my AntiSplat crank vacuum gizmo would mitigate the blow-by pressurization if a ring broke.
I have an AntiSplat exhaust air valve with the Napa CRB 229000 valve. There was still enough pressurization that oil was being pushed out the whistle slot in the hose leading to the exhaust air valve.
I have done some reading as to possible causes of broken rings. Many possible causes...
This may have been a ring flutter incident. As slippery as this plane is, I do occasionally close the throttle and flatten the prop pitch in descent. If I haven't done that in descent, it is always done in the pattern or prep for landing. I found some mentioning this practice as bad such as here:
https://forum.cubcrafters.com/showthread.php/2256-Engine-management
https://www.euroga.org/forums/maint...ter-applicable-to-our-aircraft-engines?page=1
And then there's this:
The Titan service letter for ring installation comes with this bold warning:
http://www.continental.aero/xPublications/xService Bulletins/Experimental PMA/SIL004/
WARNING
Hard bumping of the piston ring during installation can cause
the formation of cracks in the piston ring that may not fail
immediately; however, piston ring breakage can introduce
pieces of the ring expander between the piston and bore. This
can result in the formation of grinding type cracks on the bore
surface and may cause complete catastrophic engine failure.
In reading I found an educated post on another forum by Kevin Mead:
https://www.pilotsofamerica.com/community/threads/lycoming-stuck-ring.67359/page-2
We have this problem all of the time with the Mirage and Matrix Lycoming engines. At first nobody wants to believe it's a cylinder problem. I have found the oil control ring stuck, but in most cases it's broken.
The oil consumption will drop immediately, normally as bad as 1 qt per hour. I've seen one broken oil ring cause a consumption of 4 qts in an hour. The 2 compression rings will be good and the compression check will be 80/80. There is so much oil in the cylinder leading to great compression. Another symptom will be a bad mag check on the first flight of the day. Oil consumption is at it's worst in the flight levels too.
What's funny is that I can pull pieces of the oil control ring and it's spring out of the suction screen but the cylinder wall is not damaged.
I had two calls in the last month about sudden high oil consumption on the Lycoming TIO540 engine. So much consumption that they landed with very little oil. In both cases it was a broken oil control ring. Sudden consumption has been a bad turbo many times too, oil loss is so fast in those cases. This problem has been going on since the introduction of the new chrome edge cast iron oil control rings in 1994, So many times the people that where forced down continued flight after adding 6 qts of oil or more at the last stop.
My common findings.
Compression will be good. There's extra oil providing a better seal.
Normally a bad mag check, oil on a plug. An engine monitor will take you to the offending cylinder.
Many times pieces of the oil control ring are in the suction screen.
Normally the cylinder wall isn't damaged, I don't know how.
I find the rings broken in the box that is in a new cylinder kit.
I have also had the same problems on the Turbo Saritoga and the Machen converted Aerostar TIO540-S1AD and -U2A engines.
Want to see higher consumption? Take it up high.
Many of the people that continued flight had a dead and destroyed engine by the time they made it down from the flight levels.
The training must be good, very few off field emergency landings.
It's really bad that nothing has been done to end this problem.
Kevin states sudden high oil consumption. This is important as it was the case with my broken ring. While I don't know when the ring broke, I did see sudden high oil consumption. It changed from a quart every 5-6 hours to a quart an hour the next flight. I also had an oily plug on the #3, the cylinder with the broken ring. The compression test was 75+/80 on all cylinders in spite of the broken ring. I would suggest that a broken ring be high on ones differential diagnosis list when confronted with these symptoms. Unfortunately, the only way to know is to make the decision to pull the cylinder.