231 cylinders

[DonMuncy]

I had heard about how 231s had "cylinder problems". So I was not surprised to find the engine log showed my plane had a cylinder replaced in 1997 due to "low compression", and another in 99 because of "no compression", (before I bought the plane). I was not too surprised when in '05 my A&P told me I had to replace a cylinder with low compression. And again in 2010, at an annual, I had a low compression cylinder and "had to" replace it.

Then I attended one of Mike Busch's webinars in which he told us about a Continental Service Bulletin (SB03-3) which basically says if you find a low compression reading on a cylinder, you should fly the plane at cruise power for a period of time (about 45 minutes) and recheck the compression.

So at my annual this month, the A&P called and said one cylinder was low and needed replacement. I told him about the SB and asked him to follow Continental's recommendation. He said he would, but he didn't have much hope.

Today he called. He said after the flight, that cylinder pressure was within the normal range.

Are all 231 owners as slow as I am, or am I the only one with a history like this.

[Lood]

A friend of mine bought a 1982 model 231 with 200 hrs total time. He flew it for 25 years before the engine was TIMEX, or actually 50 hours before and replaced with a factory reman. His engine was never opened during this 25 years and I'm sure it must be due to the manner in which he flies.

On take off, he would never go higher than 35", climb at 30" and he always cruises at 26" in the normal non-turbo levels of 10k feet and below. At this power setting, he gets around 165 kt burning only 9.5 gal.

It is my opinion that his engine never really worked hard and it lasted its lifetime - cylinders and all.

[DonMuncy]

I didn't mention how I fly. I generally use 39 inches for take off and cruise at 30-31. If you have never flown a 231, you won't know how difficult it is to use a very specific MP. Anytime you advance the throttle, the MP will lag and then surge. (At lest mine does). If you are at 29 and move the throttle the tiniest amount it will run up to 32, and if you retard a tiny amount it may go to 30, or 28. And any change in RPM will necessitate the tiny see-sawing to get back where you were.

Your friend flies very conservatively. I am not that conservative, but have never felt I abused my engine.

[KSMooniac]

Don, do you fly LOP or ROP, and what are your typical CHTs and fuel flows?

[DonMuncy]

I have occasionally flown LOP, but generally ROP. My wife is almost always with me and she complains when she hears to slight burble with LOP. I generally keep my CHTs under 380. My fuel flow is generally around 12.5, but of course this varies.

[Jeev]

A friend of mine bought a 1982 model 231 with 200 hrs total time. He flew it for 25 years before the engine was TIMEX, or actually 50 hours before and replaced with a factory reman. His engine was never opened during this 25 years and I'm sure it must be due to the manner in which he flies.

On take off, he would never go higher than 35", climb at 30" and he always cruises at 26" in the normal non-turbo levels of 10k feet and below. At this power setting, he gets around 165 kt burning only 9.5 gal.

It is my opinion that his engine never really worked hard and it lasted its lifetime - cylinders and all.

That's all peachy but why not just buy a J if you are going to fly like that?

There are many turbo Mooneys on my field and they are all flown differently but the constant is during the time between overhaul they all expect to buy a couple cylinders. With that being said if you find yourself doing a full top O/H before mid time I would review your SOP.

Your method of flying a low comp cylinder as worked for me in the past. Good luck.

[Lood]

Relax guys, everybody flies his or her airplane whichever way they like. Be it whatever type or model and everybody will defend his or her method with their own explanation, to be the best. Although I don't have any PIC experience on 231's, I was just commenting on the original post, because I know that it's SOP to have cylinder work done somewhere along the way before TBO on most Continentals - also true for the IO360 used in the 231, but in my friends' case, this never happened.

I also know that no two engines of the same model react the same, despite being treated exactly similar. That's seen all the time on twins.

Why didn't he just buy a J? Well, I guess because he could afford to buy an almost brand new 231 back in '82 and fly it like a J for the following 25 years.

[Lood]

Double post.

[231LV]

I have occasionally flown LOP, but generally ROP. My wife is almost always with me and she complains when she hears to slight burble with LOP. I generally keep my CHTs under 380. My fuel flow is generally around 12.5, but of course this varies.

Flying ROP, the CHT's can get really hot which would explain the relatively frequent replacements (whether necessary or not) you have undertaken. Given that you keep the CHT's below 380 while running ROP, heat would not account for your experience however, while ROP, your flame front is burning more quickly in the cylinder causing the piston to barely be on the downstroke as it receives a huge "hammer" from the power stroke.....this doesn't help the longevity of the jugs or the pistons.

Since this isn't a ROP/LOP thread...I will say no more.......

[kortopates]

I really don't believe ROP per se is burning up cylinders any more than LOP does. Its all about how much ROP or LOP in the context of power setting. I can't tell from MP and fuel flow alone what power setting is being targeted for cruise. But it appears near the POH's recommended MAX cruise. If so, FWIW, I found the POH recommendations for fuel flow at max cruise to close to peak for my comfort. To get all the cylinders > 100F ROP, (mostly near 150 ROP at max cruise), I found I needed to add ~1 GPH - thus my ROP max cruise @78.6% power is with 13.6-8 GPH vice POH of 12.5GPH. (On the other side, my max LOP cruise is 70% at 11 GPH, 80 LOP - limited conservatively by JPI TIT of 1575F.) If you haven't already, you may want to check just how far ROP your cruise settings really are.

Overall though, our TSIO cylinders really take a beating operating at max cruise power levels, but I didn’t get a Turbo to fly it like a J. So I too planned for a cyl replacements but so far I have only had an issue with my coolest front cylinder that probably hasn’t ever gotten above 350F. Go figure. All the others, including my middle hottest running cylinders are all doing extremely well at 1200+ hrs.

Incidentally, there is much more to the TCM SB mentioned, including real minimum pressure based on the calibrated orifice reading, not to rely on the first low reading as you pointed out and the need to borescope etc.

[KSMooniac]

Paul, do you borescope your cylinders regularly? Getting to 1200 hours is commendable, and I wonder how your exhaust valve heat patterns look. Any idea when the cylinders were made or overhauled?

[kortopates]

Scott, Yes until recently my shop on the field, CrownAir, borescoped every annual. Although I took over most of the maintenance a few years ago, this was the first year I did my own annual (with an IA) and I procured an Autel 8.5 borescope to keep it up.

My engine was majored with J&J overhauled Cerminil cylinders (from Texas) that have 1225 hrs on now. Although the pistons and everything else in the cylinders were replaced with new (except for the rocker arms which were rebushed), the cylinders themselves were not new and I have no idea how many hrs the cores may have had. That's always given me some concern for their longevity but I've been pleased so far - knock on wood. So far though I am pretty impressed with J&J cylinders and they are very competively priced. WRT to burn pattern, I didn't have any center orange/red going near the edges and the orange/red centers were pretty symmetrical as best as I recall. Given these new borescopes have video and picture capability it really makes sense to capture pics for historical purposes; especially as I learn more about what to look for. I just need to put a memory card in the scope to do so.

[Parker_Woodruff]

I need to take a look at the logs, but my cylinders are approaching 1000 hours in service.

11.6 - 12.0 GPH LOP all day if I'm travelling. 9.0-10.8 GPH LOP if I'm just cruising locally.

Need to call up GAMI for a small adjustment on #2 and possibly #6 now that I'm certain all induction and ignition issues are fine.

[KSMooniac]

My IA and I just started recording pics this year for historical trend tracking, and I think it is a great way to use this new (affordable) technology. I always understood the trouble with Continental cylinders to be the valve geometry issues, so I'm not surprised an overhauled unit and unknown hours but (presumably) good valve installation to give good service past 1000 hours.

[gfhughes]

In one annual of my 231 by Paul Lowen, he found low compressions and flew it at full power for half an hour. Compressions became normal and all cylinders went to engine final removal.

My current (third) LB1B needed #2 cylinder replaced at 1300 hours. "Just worn out, not "overhaulable."

[chrisk]

Hi All,

I'm thinking of buying a 231, and this discussion seems to be very appropriate. The plane I am looking at has about 900 hours on the engine and all cylinders are around 75/80, except one. It is at 60/80 and has been this way for the last 3 annuals. The owners mechanic says this is nothing to worry about. Opinions sought.

Thanks

Chris

[DonMuncy]

My opinion only: If I found this on my plane, I would not worry about it. I don't think it is a problem. However, if I was about to buy the plane, I would want a 1AMU discount off the price, to offset the possibility it would have to be replaced somewhere down the line.