Cylinder #3

[philiplane]

check for intake leaks. They will cause cylinder imbalance that worsens as you lean.

[NJMac]

The higher #3 EGT seems irrelevant, unless that's been a recent change.  Check the EGT sensor probe, mine partly backed out of the hole once, and needed to be resecured.
Is there a chance your fuel flow transducer has not been calibrated correctly, or that your JPI has the wrong K-factor entered for your transducer?  13.3 gph seems almost impossibly rich at 24/2400.  From my POH, best power is at 10.2 gph.  That seems like pretty much full rich, and if your motor requires full rich just to run, that seems very wrong.  It might mean you have a really weak ignition system, but I'd put more money on it being a fuel flow calibration problem.  Do you have a factory fuel flow you can cross check it with, or have you confirmed the fuel flow with your refueling?

#3 has always had a hotter egt. For a few months #2 took that place but now it's back to #3 and seems to be getting hotter with each flight, relative to the other 3 temps.

Fuel flow seems to be pretty close when I first had it installed but don't keep track of it that closely TBH.

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[NJMac]

check for intake leaks. They will cause cylinder imbalance that worsens as you lean.

When they cleaned the injectors, they also checked for intake leaks said they found none but you're not the first to suggest this.

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[Shadrach]

If you are unable to lean, I would suspect an ignition problem on #3 at cruise power.  I've had plugs pass a mag check on the ground that go cold above 2000rpm. Full rich + single point of ignition equals very slow flame front as compared to the other cylinders. That energy would go out of the exhaust (high EGT) not the cylinder (high CHT).

Raw EGT numbers can matter and may be important here in your situation.  An IO360A1A with a healthy ignition system will produce max EGT readings in the 1480 to 1550 range depending on DA, throttle position and probe position.  The IO360A1A leaned to 100ROP at  24inHg and 2400rpm should yield a fuel burn of about 10.5gph.  You are showing 13.3gph and 1377°.  Seems unlikely that 1377° is 2.5ish gph from 100ROP.  I suspect that you cannot lean to 10.5gph  without some degree of roughness.  This could be ignition related or fuel related.  The low CHT and relatively Higher EGT has me leaning towards ignition.   

A bit about raw EGT numbers...

Raw EGTs don't mean much by themselves, but combined with other data like fuel flow and CHT can certainly be telling.  A lot of folks are repeating the "Raw EGT numbers don't matter" sentiment originally made by GAMI and then spoken and published by many other columnists.  However, the context of the statement is important.  Pilots sometimes (less prevalent than it used to be) think of raw EGT numbers rather than using degrees from peak EGT as a reference.  I have had many pilots tell that their engine is well balanced stating that "all EGTs are within 25 degrees of one another".  An engine may be quite well balanced with or without EGTs that are close together in raw temp numbers. The raw numbers don't matter. This is the fundamental misunderstanding that GAMI (and others) are attempting to correct. While it's true that raw EGT numbers aren't a concern in most cases, that does not mean they don't tell us anything.  I have heard or seen  John Deakin, Walt Atkinson and George Braly (all GAMI instructors) use 1200ish as a goal for full rich, max power EGT for NA engines and 1300ish for turbo's.  I assure you that if you told any of them that EGT was in the 1400s on take off, none of them would say "EGT numbers don't matter"... An abnormal raw EGT number is something to be investigated not dismissed.

Edited June 15, 2020 by Shadrach

[Shadrach]

44 minutes ago, NJMac said:

 

 

#3 has always had a hotter egt. For a few months #2 took that place but now it's back to #3 and seems to be getting hotter with each flight, relative to the other 3 temps.

Fuel flow seems to be pretty close when I first had it installed but don't keep track of it that closely TBH.

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# 3 is typically the leanest cylinder on most A1As without GAMIs (most do not need them). It is also the typically the hottest CHT as it's configuration and proximity to the rear baffle seal give it less than optimal cooling air. This can be improved.

[Shadrach]

46 minutes ago, NJMac said:

When they cleaned the injectors, they also checked for intake leaks said they found none but you're not the first to suggest this.

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IF you had an Intake leak, I would expect that cylinder would be leaner relative to the rest and therefore producing more power while ROP thereby producing higher CHTs (which it is not).

[mooniac15u]

On 6/13/2020 at 5:02 PM, NJMac said:

 

I keep seeing high temps on cylinder #3 on my M20E. Had the mechanic clean the fuel injectors last year and nothing improved. Can hardly lean the mixture wanting to stay around 1400-1415 EGT, ROP. It won't run well LOP. Would you accept this as is or do I ask for some specific digging with my annual in a week?

 

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Are you unable to lean because you are trying to hit an arbitrary EGT number?  Or is it causing some actual problem with the engine when you try to lean?

[NJMac]

Are you unable to lean because you are trying to hit an arbitrary EGT number?  Or is it causing some actual problem with the engine when you try to lean?

I was taught for short hops like most of mine, 45 mins in the air, to lean to 100 ROP. I found peak to be 1515 so I usually lean the hottest cylinder to 1410 or so making fuel flow about 12.5gph.  If #3 was similar temps with the others, I really think 10ish gph would be possible.

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[NJMac]

If you are unable to lean, I would suspect an ignition problem on #3 at cruise power.  I've had plugs pass a mag check on the ground that go cold above 2000rpm. Full rich + single point of ignition equals very slow flame front as compared to the other cylinders. That energy would go out of the exhaust (high EGT) not the cylinder (high CHT).
Raw EGT numbers can matter and may be important here in your situation.  An IO360A1A with a healthy ignition system will produce max EGT readings in the 1480 to 1550 range depending on DA, throttle position and probe position.  The IO360A1A leaned to 100ROP at  24inHg and 2400rpm should yield a fuel burn of about 10.5gph.  You are showing 13.3gph and 1377°.  Seems unlikely that 1377° is 2.5ish gph from 100ROP.  I suspect that you cannot lean to 10.5gph  without some degree of roughness.  This could be ignition related or fuel related.  The low CHT and relatively Higher EGT has me leaning towards ignition.   
A bit about raw EGT numbers...
Raw EGTs don't mean much by themselves, but combined with other data like fuel flow and CHT can certainly be telling.  A lot of folks are repeating the "Raw EGT numbers don't matter" sentiment originally made by GAMI and then spoken and published by many other columnists.  However, the context of the statement is important.  Pilots sometimes (less prevalent than it used to be) think of raw EGT numbers rather than using degrees from peak EGT as a reference.  I have had many pilots tell that their engine is well balanced stating that "all EGTs are within 25 degrees of one another".  An engine may be quite well balanced with or without EGTs that are close together in raw temp numbers. The raw numbers don't matter. This is the fundamental misunderstanding that GAMI (and others) are attempting to correct. While it's true that raw EGT numbers aren't a concern in most cases, that does not mean they don't tell us anything.  I have heard or seen  John Deakin, Walt Atkinson and George Braly (all GAMI instructors) use 1200ish as a goal for full rich, max power EGT for NA engines and 1300ish for turbo's.  I assure you that if you told any of them that EGT was in the 1400s on take off, none of them would say "EGT numbers don't matter"... An abnormal raw EGT number is something to be investigated not dismissed.

Excellent feedback. Appreciate your input. Would a mag check at altitude help ID this or how would I try and help the mechanic with this theory?

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[Shadrach]

2 minutes ago, NJMac said:

Excellent feedback. Appreciate your input. Would a mag check at altitude help ID this or how would I try and help the mechanic with this theory?

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A high power, in flight mag check would indeed help to rule out an ignition problem.  Can you lean to 10.5 GPH?   24inHg and 2400RPM should yield ~ 10.4 on a standard day. A little more when the OAT is on the cold side and a little less when it's warm side. See POH attachment.

 

Edited June 15, 2020 by Shadrach

[N231BN]

For an intake leak to significantly affect a fuel injected engine it would also have an effect on idle RPM(high idle). What are the numbers on takeoff or when WOT?

[mooniac15u]

1 hour ago, NJMac said:

I was taught for short hops like most of mine, 45 mins in the air, to lean to 100 ROP. I found peak to be 1515 so I usually lean the hottest cylinder to 1410 or so making fuel flow about 12.5gph.  If #3 was similar temps with the others, I really think 10ish gph would be possible.

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Have you verified that 1515 is still peak for cylinder #3?

[NJMac]

Just now, mooniac15u said:

Have you verified that 1515 is still peak for cylinder #3?

Its been a while but Im 99% certain I can say yes to this. 

[NJMac]

10 minutes ago, N231BN said:

For an intake leak to significantly affect a fuel injected engine it would also have an effect on idle RPM(high idle). What are the numbers on takeoff or when WOT?

I dont recall FF but it gets over the 2700 rpm redline unless I back it down. 

[Shadrach]

On 6/15/2020 at 12:28 PM, NJMac said:

Its been a while but Im 99% certain I can say yes to this. 

Air density and temp will affect EGT reading. It's not always the same.  However, it should remain within the same general range for a given DA.

Edited June 29, 2020 by Shadrach

[N231BN]

I dont recall FF but it gets over the 2700 rpm redline unless I back it down. 

How about the EGT spread? To be frank, you need to verify you don't have a spark plug breaking down before messing with anything else.

[jaylw314]

On 6/15/2020 at 7:20 AM, NJMac said:

#3 has always had a hotter egt. For a few months #2 took that place but now it's back to #3 and seems to be getting hotter with each flight, relative to the other 3 temps.

Fuel flow seems to be pretty close when I first had it installed but don't keep track of it that closely TBH.

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If it's changing, that's useful information.  A spark plug not firing every cycle will indeed increase your EGT in that cylinder, and as it fails to fire more often the EGT will increase to the same amount it rises during a mag check.  Alternatively, a weakening ignition system may be affecting what happens to be your weakest spark plug.

The fuel flow is still way off and the fact that it exceeds redline at full power suggests either your fuel flow is not calibrated correctly or your fuel metering system is borked.  In either case, it's worth following up on

[NJMac]

Checked the fuel used per EDM, 18.7 gals on last trip and the FBO said they added 18.2. K factor isn't dead on but not too far off, guess that's 5% error?

 

Flew first leg of my trip today solo so had a chance to play with lean find on the EDM. Pics attached. It actually ran really well LOP but the monitor started flashing at me red for the temps being too high. EGT went as high as 1650 before I bailed and went back full rich to start leaning as I had in the past. I could have sworn it peaked at 1550 last year when I first got into this idea, hence my 1415 target. I ran #3 up to 1460 so the othera were closer to 1380 and it seemed happy. Pending AGLs findings next week at annual, I'm wondering if a sensor isn't hating its life?

 

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[NJMac]

What a difference a new set of plugs makes. Flew home Fri around midnight, 20/25, 8k msl, 60% power at 10.2gph with #1 and #3 dancing between the hottest EGTs around 1415. Quite happy with the difference.

 

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[N231BN]

What a difference a new set of plugs makes. Flew home Fri around midnight, 20/25, 8k msl, 60% power at 10.2gph with #1 and #3 dancing between the hottest EGTs around 1415. Quite happy with the difference.
 
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Glad you got it figured out.

Did you ever try an in-flight mag check before changing plugs?


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[NJMac]

1 hour ago, N231BN said:

Glad you got it figured out.

Did you ever try an in-flight mag check before changing plugs?


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To be honest, I completely forgot. I focused on running the lean find on the JPI but didnt do the mag check. 

[Shadrach]

3 minutes ago, NJMac said:

To be honest, I completely forgot. I focused on running the lean find on the JPI but didnt do the mag check. 

Now that the ignition issue is sorted.I’m curious what your full rich, take off EGTs look like. 

[NJMac]

Just now, Shadrach said:

Now that the ignition issue is sorted.I’m curious what your full rich, take off EGTs look like. 

from memory, they were around 1470 as I was climbing 110 IAS.  

[Shadrach]

Just now, NJMac said:

from memory, they were around 1470 as I was climbing 110 IAS.  

Doubtful. No way that 1470 is any where near the desired 250-300° ROP setting for full rich. Wide open throttle and full rich should be <1300, in fact most of mine run mid to high 1100s.

[Ragsf15e]

13 minutes ago, Shadrach said:

Doubtful. No way that 1470 is any where near the desired 250-300° ROP setting for full rich. Wide open throttle and full rich should be <1300, in fact most of mine run mid to high 1100s.

Agree.  Many people use their full rich, SLtakeoff egt for their “target egt” as they lean during climb.  A lot of us know our takeoff egt.  Mine is about 1200-1225ish.