M20K engine cylinder #2 low CHT and strange sound when running

[JC2020]

I recently realized two stand-alone issues with the TSIO-360-LB engine. Cylinder #2 has a CHT lower than others by 70F during taxi or low-power settings (<30%), spark plugs in this cylinder tend to be fouled as if this cylinder always runs richer than others. Cruising performance seems normal (CHTs same for all cylinders, EGTs same for all, and all other parameters are green). all compression numbers are normal. Could this problem result from a bad fuel distributor?

When the engine is running, there's a noticeable sound in a fast rhythm like '"Dah, Dah, Dah, Dah", or a roll with paddles surrounding and hitting things. Again, performance and instruments seem normal. Don't know for sure if it's normal.

 

[carusoam]

JC,

In the modern days…

People often share their engine data when discussing their observations…

videos captured in flight, with the sound on… often fill in many details…

1) First steps are to determine if you have an instrument problem, or an engine problem…

2) Instrument problems are easy…

3) Engine problems are expensive….

4) what is the background of your motor… age and hours are always helpful…

5) If you have an engine monitor… lets get the data out of it… posted to savvy, then click the share button… copy the link here…

6) It is difficult to discuss the weather around here without confusing everyone…. Engine challenges are 4X more difficult…. 

7) Complexities of typing, reading, and understanding…

Let’s start at the top!

Best regards,

-a-

[anthonydesmet]

Engine data with a gammi lean test would be nirvana….

[jlunseth]

10 hours ago, JC2020 said:

I recently realized two stand-alone issues with the TSIO-360-LB engine. Cylinder #2 has a CHT lower than others by 70F during taxi or low-power settings (<30%), spark plugs in this cylinder tend to be fouled as if this cylinder always runs richer than others. Cruising performance seems normal (CHTs same for all cylinders, EGTs same for all, and all other parameters are green). all compression numbers are normal. Could this problem result from a bad fuel distributor?

When the engine is running, there's a noticeable sound in a fast rhythm like '"Dah, Dah, Dah, Dah", or a roll with paddles surrounding and hitting things. Again, performance and instruments seem normal. Don't know for sure if it's normal.

 

The induction system in the TSIO360 LB or GB is not ideal. There is a straight log or manifold that splits the induction air at the front and runs along both sides of the engine. It ends in a flat cap near the firewall. This means that the rearmost cylinders, which are #1 & #2, are at the far end and the induction air gets tapped off by 6, 5, 4, & 3 before it can ever get to #1 & 2. On startup and low idle, the turbocharger is not boosting much and hence 1 & 2 are barely operating. If you give it a little throttle, say 1100-1200 rpms, they will come on line. In my engine 1 & 2 may not even show a CHT at low idle because the minimum that my monitor displays is 240 and they are operating below that. It is not abnormal and does not mean there is something wrong with those cylinders. Actually, at cruise, my #2 is the hottest because it is furthest back and gets the least cooling airflow and because the baffling is not great back there. Like you, I worried about it when I first got the aircraft and a good monitor and saw the temps, but after 12 years of the same thing I don’t worry. I know what is happening.There is actually a way on my monitor to get the low temps on 1 & 2 displayed (put the monitor in “Normalize” mode) but I don’t bother, it is not important. What is important is that 1 & 2 show up operating normally during your run up.

As for the sound, would have to hear it to tell you if it is abnormal. We have a thing called “autoroughs” when flying over a large open body of water. Every pilot’s engine starts to sound weird. The point is our ears are not the best indicator. That said, I always check out everything that seems abnormal about the engine because sometimes it is.

Edited April 6, 2023 by jlunseth

[carusoam]

Awesome post again JL!  
 

Great M20K details and a pic!

Best regards,

-a-

[jlunseth]

Thanks Anthony. Took that pic at last annual because I got tired of explaining it all in words.

To the OP. I noticed you have trouble with plug fouling. Maybe you know this, but on start up and for taxi you need to lean to what is called “idle rise.” So if you set the power to make, say, 1100 RPMs at full rich right after start up, you then lean the engine out. If you have a good monitor you will see r the RPMs rise by around 75 as you lean. That should be your fuel setting for idle and taxi. That will help with the fouling, I don’t get fouling or if I do it is minor.

The other place to stay lean is on final. The standard advice is to put the mixture in full rich just in case you have to go around. However, if you do that  in the TSIO360LB the engine will burble on final. It is not a true miss, but some of the cylinders are drowning in fuel and early in my 231 career I had people on the ground tell me my engine was missing. I keep the engine pretty lean on final. If I have to go around I just put the fuel in full, along with the manifold pressure. Once you are on the ground you need to make the mixture richer, not necessarily full rich but somewhere slightly richer than that idle  rise setting. You are going to be accelerating the engine for some taxi operations and it needs to be a little richer for that. But if you keep it lean on final you will have less trouble with fouling. 

Full rich, full power for takeoff and climb though. That is the reason the engine is set up so rich, it needs rich fuel flow at full power to keep the engine cool.

[JC2020]

6 hours ago, jlunseth said:

Thanks Anthony. Took that pic at last annual because I got tired of explaining it all in words.

To the OP. I noticed you have trouble with plug fouling. Maybe you know this, but on start up and for taxi you need to lean to what is called “idle rise.” So if you set the power to make, say, 1100 RPMs at full rich right after start up, you then lean the engine out. If you have a good monitor you will see r the RPMs rise by around 75 as you lean. That should be your fuel setting for idle and taxi. That will help with the fouling, I don’t get fouling or if I do it is minor.

The other place to stay lean is on final. The standard advice is to put the mixture in full rich just in case you have to go around. However, if you do that  in the TSIO360LB the engine will burble on final. It is not a true miss, but some of the cylinders are drowning in fuel and early in my 231 career I had people on the ground tell me my engine was missing. I keep the engine pretty lean on final. If I have to go around I just put the fuel in full, along with the manifold pressure. Once you are on the ground you need to make the mixture richer, not necessarily full rich but somewhere slightly richer than that idle  rise setting. You are going to be accelerating the engine for some taxi operations and it needs to be a little richer for that. But if you keep it lean on final you will have less trouble with fouling. 

Full rich, full power for takeoff and climb though. That is the reason the engine is set up so rich, it needs rich fuel flow at full power to keep the engine cool.

Thank you so much for your two posts, jlunseth! I totally agree with you on the opinions regarding air induction design and lean technique especially on final (in fact I was practicing that). I just get a chance to download the data from the engine monitor and will wait for Savvyaviation's analysis input. Somehow I feel the airflow will cause both #1 and #2 to run richer, not just #2. How do you feel about it?

[JC2020]

On 4/5/2023 at 11:24 PM, carusoam said:

JC,

In the modern days…

People often share their engine data when discussing their observations…

videos captured in flight, with the sound on… often fill in many details…

1) First steps are to determine if you have an instrument problem, or an engine problem…

2) Instrument problems are easy…

3) Engine problems are expensive….

4) what is the background of your motor… age and hours are always helpful…

5) If you have an engine monitor… lets get the data out of it… posted to savvy, then click the share button… copy the link here…

6) It is difficult to discuss the weather around here without confusing everyone…. Engine challenges are 4X more difficult…. 

7) Complexities of typing, reading, and understanding…

Let’s start at the top!

Best regards,

-a-

7 hours ago, jlunseth said:

Thanks Anthony. Took that pic at last annual because I got tired of explaining it all in words.

To the OP. I noticed you have trouble with plug fouling. Maybe you know this, but on start up and for taxi you need to lean to what is called “idle rise.” So if you set the power to make, say, 1100 RPMs at full rich right after start up, you then lean the engine out. If you have a good monitor you will see r the RPMs rise by around 75 as you lean. That should be your fuel setting for idle and taxi. That will help with the fouling, I don’t get fouling or if I do it is minor.

The other place to stay lean is on final. The standard advice is to put the mixture in full rich just in case you have to go around. However, if you do that  in the TSIO360LB the engine will burble on final. It is not a true miss, but some of the cylinders are drowning in fuel and early in my 231 career I had people on the ground tell me my engine was missing. I keep the engine pretty lean on final. If I have to go around I just put the fuel in full, along with the manifold pressure. Once you are on the ground you need to make the mixture richer, not necessarily full rich but somewhere slightly richer than that idle  rise setting. You are going to be accelerating the engine for some taxi operations and it needs to be a little richer for that. But if you keep it lean on final you will have less trouble with fouling. 

Full rich, full power for takeoff and climb though. That is the reason the engine is set up so rich, it needs rich fuel flow at full power to keep the engine cool.

Hi both, I have put the engine data picture from JPI here. Also, I contacted Savvy Aviation and will wait for their input.

Thanks!

[Fly Boomer]

2 hours ago, JC2020 said:

Hi both, I have put the engine data picture from JPI here. Also, I contacted Savvy Aviation and will wait for their input.

Thanks!

I haven't been following this very closely, but I wonder if you would get something like this if one plug packs it in?

[carusoam]

On 4/7/2023 at 3:05 PM, JC2020 said:

Hi both, I have put the engine data picture from JPI here. Also, I contacted Savvy Aviation and will wait for their input.

Thanks!

JC,

CHT2 clearly isn’t behaving the same as the rest… slow to come up to speed and fast to drop off…

I would rather see the EGTs… the CHTs are following what is going on in the inside… EGTs are closer to the inside challenge…

See if you can share the link where these graphs came from…

+1 for Savvy’s skill at reading the data.p and making decisions…

 

Run-ups with nice slow transitions between key positions are really helpful…

Best regards,

-a-

[carusoam]

On 4/7/2023 at 5:22 PM, Fly Boomer said:

I haven't been following this very closely, but I wonder if you would get something like this if one plug packs it in?

One plug going on vacation….

1) Drops the CHT a bit… as excess fuel gets past the exhaust valve…instead of burning inside the cylinder.

2) EGT increases as the excess fuel burns in front of the EGT sensor instead…

3) Dead plug becomes super noticeable during the single mag part of the run-up… EGT drops out immediately.

4) Using CHT data… there is a ton of time lag going on…   EGT data would be more definite…

 

Quick trouble shooting uses both EGT and CHT data, then FF and other parameters as required…

PP thoughts only, JC has been approved to spend money at Savvy!  

Best regards,

-a-

 

[jlunseth]

It difficult to interpret that data without the rest of it, the FF, RPMs, EGTs. I think you should have a mechanic look into it, but I still would not be surprised if the verdict is that it is not abnormal. As I said earlier, tempwise, 1 & 2 are behind the rest of the pack during ground ops especially if RPMs are less than 1050-1100. If you have a good engine monitor you will also see buss voltage dropping because the alternator output is not enough below about 1050, this is a long known issue in the 231. I can't say I have paid much attention to temps during final, I am normally looking at other things. As between 1 & 2, my #2 is the coldest on the ground but it is definitely there during runup and any powered up ops.

 

Edited April 9, 2023 by jlunseth

[PT20J]

If this is a new issue I might check for an induction leak. They often affect idle where fuel flows are low but are not evident at higher power where the turbo is pumping a lot of air and the fuel flows are higher.

[Guest]

On 4/6/2023 at 12:09 AM, JC2020 said:

I recently realized two stand-alone issues with the TSIO-360-LB engine. Cylinder #2 has a CHT lower than others by 70F during taxi or low-power settings (<30%), spark plugs in this cylinder tend to be fouled as if this cylinder always runs richer than others. Cruising performance seems normal (CHTs same for all cylinders, EGTs same for all, and all other parameters are green). all compression numbers are normal. Could this problem result from a bad fuel distributor?

When the engine is running, there's a noticeable sound in a fast rhythm like '"Dah, Dah, Dah, Dah", or a roll with paddles surrounding and hitting things. Again, performance and instruments seem normal. Don't know for sure if it's normal.

 

The fuel flow manifold/divider really is only in the picture when at low power and would/should affect all cylinders equally.  We just replaced one on a 360 that had poor idle.

How many hours since the fuel nozzles cleaning? 300 hours is Continental’s recommended time.  How many hours since the fuel injection system was checked?  Also look at the drain manifold under the cylinders, the small rubber seals wear out causing intake leaks at idle and weird idle performance.

[Guest]

On 4/6/2023 at 10:34 AM, jlunseth said:

The induction system in the TSIO360 LB or GB is not ideal. There is a straight log or manifold that splits the induction air at the front and runs along both sides of the engine. It ends in a flat cap near the firewall. This means that the rearmost cylinders, which are #1 & #2, are at the far end and the induction air gets tapped off by 6, 5, 4, & 3 before it can ever get to #1 & 2. On startup and low idle, the turbocharger is not boosting much and hence 1 & 2 are barely operating. If you give it a little throttle, say 1100-1200 rpms, they will come on line. In my engine 1 & 2 may not even show a CHT at low idle because the minimum that my monitor displays is 240 and they are operating below that. It is not abnormal and does not mean there is something wrong with those cylinders. Actually, at cruise, my #2 is the hottest because it is furthest back and gets the least cooling airflow and because the baffling is not great back there. Like you, I worried about it when I first got the aircraft and a good monitor and saw the temps, but after 12 years of the same thing I don’t worry. I know what is happening.There is actually a way on my monitor to get the low temps on 1 & 2 displayed (put the monitor in “Normalize” mode) but I don’t bother, it is not important. What is important is that 1 & 2 show up operating normally during your run up.

As for the sound, would have to hear it to tell you if it is abnormal. We have a thing called “autoroughs” when flying over a large open body of water. Every pilot’s engine starts to sound weird. The point is our ears are not the best indicator. That said, I always check out everything that seems abnormal about the engine because sometimes it is.

It looks like that oil cap is worn through.

[carusoam]

Looks like an interesting source of iron oxide in the oil analysis… (?)

Steem likes to collect under the cap when not allowed to vent…

newer continental caps are SS…

half baked observation only… not a solid memory at all….

Best regards,

-a-

[jlunseth]

14 hours ago, M20Doc said:

It looks like that oil cap is worn through.

 

Thanks Clarence. New engine is going in this month. Hopefully that will take care of that tired old oil cap from 2002, and a few other things. During the winter our practice around here is to keep the engine heater plugged in full time and crack the cap. We do that to allow moisture to vent off, but obviously, where it vents off is at the cap where it also can collect. Yeah, that is an old but has  been a faithful cap. My main concern with it was that the chain came off, so if one of the line kids pulled it off and wasn’t paying attention it would drop into the engine and the cowling would maybe need to come off. Did get that part fixed.

Edited April 10, 2023 by jlunseth