Cylinder peaks way behind others

[lithium366]

Another interesting observation - even with 60 degrees LOP engine was not running rough 

[Shadrach]

36 minutes ago, lithium366 said:

I did. Not sure how to link a previous message but I posted earlier in a thread Savvy profile with 3 leanings followed by mag check

I saw that, but it did not specify in flight. Which is what I was referring to. That being said, if your able to lean 60 beyond lean of peak, the ignition system is likely fine. Have you swapped the probes around?

[lithium366]

@Shadrach I swapped EGT #2 and #4. Same pattern with another probe. Mag check was in flight

Edited April 27, 2023 by lithium366

[PT20J]

What engine monitor do you have? How do you know that it is correct? It sounds like the engine runs fine, but there is just an unexplained issue with the EGT in cylinder 4 (or maybe 4 is correct and 1-3 are not. At 60 dF LOP, I would expect some roughness. Roughness comes from cycle-to-cycle combustion variation which occurs at any mixture but is much greater with very weak mixtures). Before tearing too far into the engine on the basis of a single measuring instrument, I would want to be sure that the instrument is accurate.

If you do measure the valve lift, I'd replace the valve cover gaskets with silicone.

[lithium366]

@PT20J data is from Dynon engine monitor. I borescoped cylinders and #4 definitely have more deposits. This aligns with it being rich most of the time

[Shadrach]

17 minutes ago, lithium366 said:

@PT20J data is from Dynon engine monitor. I borescoped cylinders and #4 definitely have more deposits. This aligns with it being rich most of the time

This is why I asked for full rich to peak EGT numbers. Most of us are between 200 and 250(better) ROP at full rich.

[PT20J]

6 minutes ago, lithium366 said:

@PT20J data is from Dynon engine monitor. I borescoped cylinders and #4 definitely have more deposits. This aligns with it being rich most of the time

What did the deposits look like? Do you have any pictures? Deposits could be due to oil. What’s oil consumption? 

Something doesn’t make sense. If the engine truly has one cylinder running considerably richer than the other three, when you can go deeply LOP, that cylinder should be putting out more power than the other three and you should get some roughness.

Has it always done this with the Dynon, or did something change? Aside from the EGT indications, are there any anomalies in the engine’s operation or is it running well?  

[lithium366]

Oil consumption is ok, 6-7 hours per 1qt. Here is a picture if a #4 valves. I previously had another engine monitor. I started noticing this issue 6 month ago once I installed dynon. I set up Dynon to start EGT readings at 1000 degrees while previous monitor showed values from 0. As you can tell 100 degrees difference on Dynon is much more noticeable because of the scale. Pictures from previous monitor show that EGT on #4 and #3 are about the same and higher then #1 and #2

Edited April 27, 2023 by lithium366

[takair]

Someone mentioned blockage in the air intake.  Might be worth checking for a migrating rag.  Would let air flow, just not well….like a dirty air filter.  Also, on the opposite end…might be worth a peak at the exhaust.  The flame tubes erode but can also collapse.  This would impede exhaust out/air in.  Don’t recall if you mentioned, how are your CHTs at various mixture settings?

[A64Pilot]

9 hours ago, Rmfriday said:

If one cylinder has a higher EGT then the rest wouldn’t that mean it is potentially running with either more air or less fuel then the other 3 cylinders?

Yes, but the issue as I see it is the unusual high peak, mixture whether by induction leaks or incorrect / worn injector etc can’t increase peak

Only thing I can think of that can is either poor ignition / retarded timing or compression, hopefully it will turn out to be ignition.

[A64Pilot]

For grins go out and do an extended mag check, by extended I mean leave it on one mag until EGT’s stabilize. See if you get an excessive EGT rise on the suspect cylinder on one mag, but not as much on the other.

Also try it leaned out as lean mixtures stress an ignition system harder.

Don’t sit out there at high power so long that you overheat of course, surely 30 sec would be long enough on each mag to confirm or deny.

This is just a shot in the dark though, but maybe you have a bad plug lead or something that’s breaking down at high power and leaner mixtures.

You can of course do this in flight, that removes any concern of overheating.

 

[JayMatt]

51 minutes ago, A64Pilot said:

Also try it leaned out as lean mixtures stress an ignition system harder.

*Mike Busch has entered the chat*

It was my understanding that peak exhaust gas temperatures stress the engine most. 

[Shadrach]

 

2 hours ago, JayMatt said:

*Mike Busch has entered the chat*

It was my understanding that peak exhaust gas temperatures stress the engine most. 

In what way does peak EGT “stress” the engine the most? It does not produce the highest internal cylinder pressure and therefore does not induce the highest CHTs. Peak EGT mixture settings are not particularly difficult for the ignition system to ignite, mixtures significantly lean of peak EGT better showcase any weaknesses in the ignition system. An argument could be made that perhaps PKGT is harder on the exhaust system, but we’re not talking about Pretty small variance in temperature across the cruise mixer setting spectrum.

After 25 years of flying recips, I have come to the conclusion that the best way to run an IO360 is as close to peak as from the lean side. Cool CHT’s, good power, and within best BFSC range. I’ve enjoyed very healthy cylinders as a result.

[JayMatt]

6 hours ago, Shadrach said:

 

In what way does peak EGT “stress” the engine the most? It does not produce the highest internal cylinder pressure and therefore does not induce the highest CHTs. Peak EGT mixture settings are not particularly difficult for the ignition system to ignite, mixtures significantly lean of peak EGT better showcase any weaknesses in the ignition system. An argument could be made that perhaps PKGT is harder on the exhaust system, but we’re not talking about Pretty small variance in temperature across the cruise mixer setting spectrum.

After 25 years of flying recips, I have come to the conclusion that the best way to run an IO360 is as close to peak as from the lean side. Cool CHT’s, good power, and within best BFSC range. I’ve enjoyed very healthy cylinders as a result.

to be honest I don't know but I've watched several of his videos lately and I wish they were more direct and to the point. But from what I gathered peak EGT is where the pressure is highest in the cylinder... no? From what Mike says the curves are not parallel and when you are lean of peak EGT you are in peak CHT and you need to lean further to get to 380 CHT. I don't know, I wanted to start another LOP thread even after reading everything I could find on here but I didn't want to get crucified.   

[A64Pilot]

Bottom line, below 75% power you can run any mixture you want to without harm. 75% cruise is higher probably than you expect. If you want to go fast likely your higher altitude and above about 7500’ it’s tough to exceed 75% for me anyway because I won’t cruise at 2700 RPM.

Another way to look at it is if your LOP you have to be at 10 GPH fuel burn to be at 75% power, another rule of thumb, don’t get out the micrometers.

Average day, if it’s cold that increases power of course

Above 75% I’d suggest be rich, very rich as I suspect at that power your after speed not economy and high power often means high temps and excess fuel helps cool things down. 

‘Once you become very comfortable and feel you really know what’s going on then if you feel the need try higher power LOP.

I’ve only got a little over 10,000 hours and flew for a living for 35 yrs or so, so I’m not yet comfortable trying high power LOP myself.

Note, 99% of my flying is LOP, but I’m way down in power, cruising about 135 kts but enjoying it.

[wombat]

1 hour ago, JayMatt said:

to be honest I don't know but I've watched several of his videos lately and I wish they were more direct and to the point  

I watch his videos on 1.75X speed on YouTube.   

[hammdo]

Ditto…

-Don

[Shadrach]

4 hours ago, JayMatt said:

to be honest I don't know but I've watched several of his videos lately and I wish they were more direct and to the point. But from what I gathered peak EGT is where the pressure is highest in the cylinder... no? From what Mike says the curves are not parallel and when you are lean of peak EGT you are in peak CHT and you need to lean further to get to 380 CHT. I don't know, I wanted to start another LOP thread even after reading everything I could find on here but I didn't want to get crucified.   

There are many threads on the subject. I think that John Deakin (RIP) wrote the most easily digested series on the subject.

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182179-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182176-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182583-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/183094-1.html

 

[Fly Boomer]

44 minutes ago, Shadrach said:

There are many threads on the subject. I think that John Deakin (RIP) wrote the most easily digested series on the subject.

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182179-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182176-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/182583-1.html

https://www.avweb.com/ownership/john-deakins-engine-related-columns/183094-1.html

 

I love reading those columns.  His writing style is both informative and funny -- good combination.  I lament that I didn't meet him until his health was beginning to fail.

[Shadrach]

35 minutes ago, Fly Boomer said:

I love reading those columns.  His writing style is both informative and funny -- good combination.  I lament that I didn't meet him until his health was beginning to fail.

I never met John in person. We exchanged  a few emails over the years when I had higher level questions. He was generous with his time and knowledge.

[Will.iam]

Could his #4 probe be mounted closer to the exhaust port than the other 3 cylinders thus showing a higher egt temperature and swaping probes doesn’t change because the swapped probe would be in the same too close mounting hole. As so many people have said egt gauges used to not have numbers so as to force the pilot to focus on the change not the absolute value of the temperature. 

[Pinecone]

3 hours ago, Shadrach said:

I never met John in person. We exchanged  a few emails over the years when I had higher level questions. He was generous with his time and knowledge.

He was a heck of a guy.  I knew him for many years on AVSIG.  We did our RH ratings at the same time and leapfrogged each other and helped each other out.  He was in town for a layover, and we grabbed a helicopter and did some fun flying around DC.

[Shadrach]

7 hours ago, Will.iam said:

Could his #4 probe be mounted closer to the exhaust port than the other 3 cylinders thus showing a higher egt temperature and swaping probes doesn’t change because the swapped probe would be in the same too close mounting hole. As so many people have said egt gauges used to not have numbers so as to force the pilot to focus on the change not the absolute value of the temperature. 

Yes many have pointed that out. However, there are scenarios where raw EGT number can be interpreted. 

maybe this is but that’s seems like a long shot. His #4 EGT is flirting with 1700°.  The only way that my engine will generate an EGT number approaching that level is to run on a single mag. 
 

@lithium366 do you have any data that shows full rich take off EGTs?  The staining on your exhaust valve is odd but the valve appears to be rotating and shows no signs of hot spots.

[A64Pilot]

1 hour ago, Shadrach said:

maybe this is but that’s seems like a long shot. His #4 EGT is flirting with 1700°.  The only way that my engine will generate an EGT number approaching that level is to run on a single mag. 
 

That’s why I’d like to see an extended mag check, to see if there is a significant difference in egt between the two, mags can cross fire etc, but unlikely both are identical malfunctions, same for plug leads.

What I’m calling an extended mag check is on each mag long enough to see EGT’s stabilize.

If the two mags are close to the same EGT, that ought to eliminate the ignition system, plugs, mags, harness etc. I’ve even seen an ignition switch cause an intermittent miss, that took awhile to find

[Fly Boomer]

12 minutes ago, A64Pilot said:

That’s why I’d like to see an extended mag check, to see if there is a significant difference in egt between the two, mags can cross fire etc, but unlikely both are identical malfunctions, same for plug leads.

What I’m calling an extended mag check is on each mag long enough to see EGT’s stabilize.

If the two mags are close to the same EGT, that ought to eliminate the ignition system, plugs, mags, harness etc. I’ve even seen an ignition switch cause an intermittent miss, that took awhile to find

I have suggested plug, wire, or mag, but he says in-flight mag check is perfect.