Running a M20K231 to TBO

[231DF]

Looking for input from people with real world experience of running a 231 all the way to TBO without IRAN/ Top Overhaul etc. 

Thanks, 

Adam

 

[hubcap]

25 minutes ago, 231DF said:

Looking for input from people with real world experience of running a 231 all the way to TBO without IRAN/ Top Overhaul etc. 

Thanks, 

Adam

 

Reach out to @jlunseth he just completed an overhaul on his engine at ~2300 hours. I know several guys who have gone to TBO on their 231. With modern engine monitors it is  quite easy to manage temperatures and take better care of our engines.

[DonMuncy]

231s have a bad reputation for not making it to TBO. I am not sure whether they will or won't, but I do firmly believe that most of them will do far better than the reputation. Mine had about 4 cylinder replacements before I got it, and on bad advice, one after I got it. This was before I figured out what was going on.  All of them were "for low compression". If you follow Continental's recommendations, when you get a low compression reading, fly it a few hours and recheck it. In virtually all cases, the compression will read different.

Also, turbo Continentals are ripe for engine temperature mismanagement. If you push the throttle full forward for take-off and leave it there, you will get in trouble. Turbo Continentals are not difficult to take care of, but you have to watch your P's and Q's.

 

[jlunseth]

I ran my engine to 2400 hrs before replacing it. It had an IRAN at about 1100, but the reason was an incident where I lost oil pressure at 19k and had to make a rapid, no power descent to a safe no power landing. According to my A&P, that caused piston slap that scored the cylinder walls, hence the IRAN. It also had a turbo rebuild at about 700 hrs, right after I got it. That turbo made it all the way to TBO without further incident. 

I firmly believe that the TSIO360LB can run to TBO and beyond, if the engine is run correctly. Unfortunately, I think that many of the original engines were not, and part of the fault falls on misleading information in the POH. For example, the CHT redline is 460 dF. If you ever hit 460 dF it is probably time for a top overhaul at least. The goal is 380 dF. During high, hot climbs in the summer, such as out of a western airport, the engine might creep up a little over 400, but if the fuel flow is set up correctly to generate at least 24.0 GPH in a full rich full power climb, the CHTs will routinely be around 380, and in the spring, fall and winter they will be lower than that. The POH also has cruise power settings with the engine at or just slightly rich of peak. This is the worst possible place to run an engine and will generate the highest Internal Cylinder Pressures. From my experience, any cruise power setting in the range of 70-75% HP or higher, where the fuel flow is 12 something GPH, is a “red box” setting, hard on the engine.

I was able to run the now-replaced engine for hundreds of hours at 11.1 GPH/2450 RPM/34” MP. The reason for the 34” is that lean of peak operation is a fuel/air ratio and you can make the mixture more lean either by reducing the fuel flow while the MP remains constant, or by adding MP while the fuel flow remains constant. So I used the 34” to make the mixture sufficiently lean to be reasonably healthy for the engine. I was concerned about the extra work this puts on the turbo so after it hit 1000 hours from the replacement I had it borescoped by my A&P several times and there were no ill effects.

The other thing to watch is cooling of the cylinders, which is affected primarily by the baffling. My old baffling was not great, but with the new engine I have been a stickler on keeping the baffling in good shape, no gaps or creases. Creases where the baffling meets the top cowling were the primary issue with the old baffling.

I am at about 150 hours on the new engine. Had to run it ROP for the first 100 hrs per TCM’s break-in instructions, and just beginning to work up LOP operations again.

The biggest issue when you buy a used aircraft is that you have no idea how the prior owner ran the engine. If they believed everything that is in the POH the engine may be doomed to an early top or IRAN already.

[Jim F]

Great writeup jlunseth thank you

I think I can add to this discussion.  I have an 81 231 with a GB, fixed waste gate, no intercooler, and 1961 hours since new.  I purchased the AC in 2010 with 1200 hours and it had two cylinders swapped out in that time.   In the 761 hours that I have put on it, I replaced one cylinder due to a crack in the exhaust port that started at a void in the aluminum that was the stress pint to start the crack.   I have always taken off at full power and climbed to cruise altitude at full power.  Full power adds the extra fuel to aid in lowers CHTs in the climb.  If you pull back to a cruise climb you will not get the extra fuel added for cooling.  Fuel is cheaper then and top overhaul.

With in the first year, I installed a JPI830, and I believe that for my AC the 830 is required equipment.  It is just too easy to overheat the engine with the single point factory installed instrumentation. 
Can you keep a GB cool enough to get to TBO, yes.  How to do that, well you need a little luck that the previous owner didn't hurt it too bad.  If there is an engine analyzer on now grab the historical data.  The LBs have a larger opening throttle body and the front intake tubes from the throttle body to Cyl #5 & #6 are a different part number and i believe they have a larger ID.  I believe that both larger IDs must be to reduce the restriction is air flow.  I reason I say it this way is that I have heard on this forum that LB run cooler, and I have a list of the GB to LB differences, but I have never seen an explanation from continental as to why these changes make the LB run cooler.  At overhaul mine will be converted to an LB.

I am blessed that I am the A&P/IA for my 231 and I am an engine guy.  Back in the day I have overhauled >500 GA engines and maybe 30ish TSIO-360s, I have set >1000 Continental fuel flows.    

To dos:

Engine baffle seals must be tight with NO leaks.  All cooling air must go through the cylinder fins.  You can have these replaced with new seal material.

Fuel flows must be set correctly by a mechanic that in experienced with fuel flows.  To set the fuel flows correctly I first ultrasonically clean the fuel injectors to remove the buildup on the metering orifice, once the injectors are reinstalled, I pressurize the intake and exhaust system with the pressure side of a clean shop vac to look for leaks.  I spray soapy water to find, and leaks and I fix any leak. 

Now I set the fuel flows with a reference to SID97-3G low unmetered fuel pressure to at 700rpm to 6.5 +/-.1psi and at full RPM(2700) and max MAP(~40ish) the metered fuel flow of ~26.7gpm and this gives me ~1400df TIT.   You can see that the metered max fuel flow I use has the added 1GPM to aid in reducing the CHT in full power takeoff and climb.  I first heard about the added 1GPM from kortopates on this forum.  This is the best single change that I have made to keep my engine cool at high power.  

(SID97-3G TSIO-360-G, GB 700 2700 40.0 6.25 - 6.75 45.0 - 49.0 16.7 - 19.3 135 - 145 23.0 - 24.7)

I would recommend that you use Savvy to review your engine data.  They do a great job giving input as to what areas need to be looked at.

Enjoy

Jim

 

 

[DonMuncy]

Does full power mean full throttle movement? Does the MP ever go above 42 inches?

[kortopates]

Does full power mean full throttle movement? Does the MP ever go above 42 inches?

No not on a 231, with a manual or fixed watergate.
Full power is redline MAP and RPM full rich.
But it is full throttle on engines with a hydraulic wastegate and controller to maintain redline like the 252, Encore, Bravo and Acclaims.


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[Steve Dawson]

Just curious on the setup for a 231 (TSIO 360 LB) with an intercooler and a Merlyn wastegate. I take off trying to hold the MP to a maximum of 37 inches / 2700 RPM then pull it back to 2600RPM, however the MP has crept easily to over 42 " where I quickly pull it back to 37".

First question: Is this the proper way to run this engine per MP and RPM and what should the fuel pressure be at 37"?

Second question: Is there a way to control MP other than the throttle? 

Steve 

[PeteMc]

On 11/13/2024 at 7:30 AM, 231DF said:

Looking for input from people with real world experience of running a 231 all the way to TBO without IRAN/ Top Overhaul etc. 

My plane had had a prop strike before I bought it and the required tear-down.  They had the shop pretty much do an overhaul and tried to sell it as XXX SMO, but the logs didn't have the signoff.  So I ended up getting a good deal.  But at around 1700hrs I had an issue with a piston pin plug.  Sure, I could have delt with the one cylinder, but figured with that time, even with the earlier work, I was not sure if I was going to be tossing money into the engine.

Current engine is at 1500hrs and still going strong.  I did have one cylinder burn a hole in the side around 1100hrs, so replaced it.  But otherwise no issues and hope to get to or beyond TBO.  The one thing that may change that is how long it currently takes to get an engine.  I'm going to be watching closely to see if the parts and shop availability gets better or not.  But as I get closer to TBO I may just get on the list to either have my engine rebuilt to get a factory reman.  Then when my date comes do I'll make the change.  The other option is to suddenly have an issue and just then start the waiting period for the engine I know I'm going to need in the not to distant future.

 

[Ethan]

I have been nicely surprised with the TSIO-360-LB. I have had two of them. The first made it to 2400 hours before overhaul and it could have gone way longer. It was topped at about 1000hours before I flew it. Then in 2018, I put a TCM remanufactured engine in the airplane and now have over 1000 hours on it. The only significant work on the engine was I refurbished the #2 cylinder because of really low compression. I run the airplane at conservative values: 31" x 2450 RPM and no more than 1500 TIT. I will run the airplane LOP if I have time to spare, but usually at 28" x 2500 rpm and I lean it to 1500 TIT - sometimes as high as 1560 - 1580 TIT.

[Jim F]

23 hours ago, DonMuncy said:

Does full power mean full throttle movement? Does the MP ever go above 42 inches?

Hi Don,

What Paul said. 

That is why I said full power and not full throttle.  With the manual waste gate if I push more throttle, I get more power.  The popoff valve (upper-deck over pressure valve) looks like it opens at 43-44in based on the max MAP readings that I have seen in the past and they can stick.  I set 37in on the takeoff roll and adjust during my scan during my takeoff roll.  I see 38-41in during my climb to altitude.  The manual wastegate makes MAP part of the primary scan.  The JPI830 is blinking red at any MAP over 40.1in so it gets my attention pretty quick.

Jim

[Ricky_231]

17 hours ago, Steve Dawson said:

Just curious on the setup for a 231 (TSIO 360 LB) with an intercooler and a Merlyn wastegate. I take off trying to hold the MP to a maximum of 37 inches / 2700 RPM then pull it back to 2600RPM, however the MP has crept easily to over 42 " where I quickly pull it back to 37".

First question: Is this the proper way to run this engine per MP and RPM and what should the fuel pressure be at 37"?

Second question: Is there a way to control MP other than the throttle? 

Steve 

This is the first time I've heard something like that. I flew a K until very recently. Same engine setup. I'd set power at 38" and 2700 RPM for take off and never saw it creep up. it'd just hold there until I would transition to "climb power" at 33" / 2600 RPM. I've seen MAP creep down if the friction lock wasn't tightened properly, but never up.

That being said, I've always increased power very gently. Increase to ~28", let the turbo pick up, which would bring it up to ~33", then add the rest to 38". Maybe you're advancing the throttle to fast and the when the turbo catches up with it it shoots up to 42"?

 

[jlunseth]

23 hours ago, DonMuncy said:

Does full power mean full throttle movement? Does the MP ever go above 42 inches?

No, not full throttle movement. "Full power" depends on your TSIO360 engine configuration. I have an intercooler so it is a little different in my engine than in the factory, non-intercooled engine. Full power in the factory engine is 40MP at 2700 RPMs per the POH. You can, but never should, exceed that limit as it is an overboost.

With the intercooler the information is a little more complicated but can be reduced to simple for actual flying. The intercooler theory is that cooling the induction air that comes out of the turbocharger increases its density and therefore its oxygen content. So there is a chart that comes with the intercooler that the pilot uses to adjust the POH settings down, depending on the Differential Temperature. The DT is the amount by which the air coming out of the turbocharger has been cooled before going into the induction system. The DT is pretty good, it ranges around 85-125 dF at cruise. Lots of people use 36" and 2700 RPMs as full power and there is nothing wrong with that. It comes out of an old article recommending using the 252 settings for the intercooled 231 engine. However, the STC for the Turboplus contains instructions for adjusting the MP downward from the POH setting in order for the A&P to make a full power fuel setting on the ground. Per the STC instructions the actual MP varies with OAT and approaches 37", although as I recall it does not quite get there. In practice, say for takeoff, I use 36" as max power even though it is a little low. But as the aircraft picks up speed that may increase a little. I don't take offense unless it reaches 37, then I will adjust it down a little. I don't like adjusting during takeoff if I can avoid it because you wind up chasing your tail (you adjust down, that slows the turbo so the adjustment winds up being more than you wanted, so you adjust back up, etc.).

The odd thing is that a setting that is a little less than full power can make the engine quite a bit hotter. I don't know the mechanics of it, but it is my perception that the fuel flow bumps up more rapidly as the engine approaches full power. So although it may be counterintuitive, a cure for a fuel flow that is showing too low and CHTs that are getting a little too hot may be to add MP rather than to subtract, because that allows the fuel flow to get to its max setting.

JimF - thanks for the comments. I too like Paul K's idea of setting the max fuel flow to 25 GPH rather than the 24 in the POH, you can always adjust it down, but once it is set on the ground you can't adjust it up, and the usual problem is that it just starts to drift down on takeoff to 20-21, and the CHTs then get warm. Also, I completely agree on the baffles, keep them as tight as possible. You are lucky you are an A&P, I keep trying to get my A&P to do what Paul recommends, sometimes it happens and sometimes not. They are getting better.

[DonMuncy]

That is why I asked. I didn't figure anyone (at least anyone with good sense) would just push the throttle to the firewall and leave it.

[Steve Dawson]

10 hours ago, Ricky_231 said:

This is the first time I've heard something like that. I flew a K until very recently. Same engine setup. I'd set power at 38" and 2700 RPM for take off and never saw it creep up. it'd just hold there until I would transition to "climb power" at 33" / 2600 RPM. I've seen MAP creep down if the friction lock wasn't tightened properly, but never up.

That being said, I've always increased power very gently. Increase to ~28", let the turbo pick up, which would bring it up to ~33", then add the rest to 38". Maybe you're advancing the throttle to fast and the when the turbo catches up with it it shoots up to 42"?

 

I'll set the MP to 37" while rolling and taking off then watch it stay there however it will creep to over 42" while climbing and cleaning up the plane unless you're constantly watchful. I'd like to be able to be able to adjust  either the wastegate or the pop off valve similar to a normal system to stop any over boosting. Unfortunately it looks like it's not possible with this system. 

[A64Pilot]

Most any engine will go to TBO if it’s not run hard. There have been a few problem children though that have defects in design. The H2AD Lycoming comes to mind.

For those that run it like they stole it or “I bought a Mooney to go fast” it’s very likely they will have less engine longevity than one run at lower power. Now there is nothing wrong with running one hard and enjoying the speed, just accept that it will impact engine longevity. The point of boosting an engine is of course to increase power whether in total or to maintain it at altitude so running one at high power is sort of the point of having a turbo.

TANSTAAFL 

I know we aren’t talking Lycoming here, but Lycoming states in a few of their pubs that for maximum engine longevity to cruise at 65% power or less.

If your trying to make an engine last first control temps, ITT and cyl head, then secondly slow down some.

 

Edited November 19 by A64Pilot

[jlunseth]

On 11/17/2024 at 5:46 PM, Steve Dawson said:

Just curious on the setup for a 231 (TSIO 360 LB) with an intercooler and a Merlyn wastegate. I take off trying to hold the MP to a maximum of 37 inches / 2700 RPM then pull it back to 2600RPM, however the MP has crept easily to over 42 " where I quickly pull it back to 37".

First question: Is this the proper way to run this engine per MP and RPM and what should the fuel pressure be at 37"?

Second question: Is there a way to control MP other than the throttle? 

Steve 

You will get a ram air effect that increases MP somewhat during takeoff. As the aircraft rolls down the runway it picks up speed, and the ram air effect is particularly pronounced immediately after liftoff when you clean the plane up. The ram air increases MP, and that increases engine output, and that increases turbo output which increases engine output further. What I do if it helps any is pretty much what you are doing, put in about 30”, let the turbo kick in, then I put in 36”. The ram air effect may add another inch to 37 or slightly higher. After I have cleaned up the plane and have control of the climb out I will adjust it back to 36”. 

There is no need to use a lot of power on takeoff. I have not found any airport anywhere, including Leadville, where 36” won’t do it for the takeoff. The 231 has ample power. Truth be told the 231 has enough power that you can do a perfectly good takeoff with 34 or 35 inches. I wouldn’t put the engine in a position where it might get to 42, which is an overboost. Keeping the power and therefore the fuel flow up during a long climb, especially a high hot climb out of a western airport, is the more important time for long term engine health IMHO.

[Steve Dawson]

Good point, I hadn't considered the ram air factor.

99% of the time I do catch or control the MP still there must be a way to limit the MP. I understand the large differences between a 252 system or for that matter most other wastegate/ turbos so I was hoping that an adjustment or different style of waste gate/ upper deck controller might have been designed for our Merlyn systems. 

One positive mention of the issue is that the turbo system is working very well 

[jlunseth]

As far as I am aware, the only aftermarket wastegate controller that is STCd for our 231s is still the Merlyn. It’s not perfect but works pretty good.