Lean mag check

[PTK]

Any comments on this lean mag check?

[Bob_Belville]

1 hour ago, PTK said:

Any comments on this lean mag check?

 

Yeah, sign up for Savvy's premium service and get Paul's expert opinion! I've learned a lot.

[Oldguy]

7 minutes ago, Bob_Belville said:

Yeah, sign up for Savvy's premium service and get Paul's expert opinion! I've learned a lot.

+1

[MB65E]

Looks like the plug for whatever mag was running was not performing. Cyl3 according to the color codes?

-Matt

[PTK]

13 minutes ago, MB65E said:

Looks like the plug for whatever mag was running was not performing. Cyl3 according to the color codes?

-Matt

How do you arrive at that conclusion cyl3?

[MB65E]

The brown line of the lower ChT, as it's not labeled CHT, but the EGT colors are labled.

-Matt

[PTK]

Just now, MB65E said:

The brown line of the lower ChT, as it's not labeled CHT, but the EGT colors are labled.

-Matt

Yes, but doesn't the corresponding EGT trace appear to register EGT? 

[MB65E]

Correct, but the fuel will still burn in the exhaust giving a false sense of heat in the exhaust, but the Cylinder looses the heat as it's not burning in the cylinder, just the exhaust. Many times the Egt will be higher as your cylinder 4 is, unless you have some leads that are swapped around. 

Clogged injector will have similar effects but effects both left and right mags. 

-Matt

[PTK]

21 minutes ago, MB65E said:

Correct, but the fuel will still burn in the exhaust giving a false sense of heat in the exhaust, but the Cylinder looses the heat as it's not burning in the cylinder, just the exhaust. Many times the Egt will be higher as your cylinder 4 is, unless you have some leads that are swapped around. 

Clogged injector will have similar effects but effects both left and right mags. 

-Matt

Ok Matt, I follow. You're saying "a" plug on cyl3 is not firing. The question now becomes which plug? The CHT3 starts to drop when I switch to rt mag and continues to drop right through both and when on left mag. It doesn't recover until I go back to both after having cycled both mags. It doesn't hont to recover when I go to both in between rt and left. Do you find it puzzling that both plugs would stop firing during rt-both-left and then start firing after finished cycling and back on both?

[Cyril Gibb]

I'd guess there are 2 separate issues. Cylinder 3 starts dropping when  you lean and recovers when you richen.  If you're LOP at that ff, then the cylinder will cool more than the others if it's a little leaner. Perhaps cylinder 3 injector picked up some fod? What does the gami spread look like?

 

[MB65E]

Not really. Cylinder temp will lag greatly vs EGT temp. All that aluminum in the head needs to be heated vs just the exhaust gas on the probe. 

I'd go after the #3 lower plug, If you thing the CHT probes are wired correctly. I've seen several cracked ceramics too. 

 Response to PTK, not Mr. Gibbs.

-Matt 

[Cyril Gibb]

3 minutes ago, MB65E said:

Not really. Cylinder temp will lag greatly vs EGT temp. All that aluminum in the head needs to be heated vs just the exhaust gas on the probe. 

I'd go after the #3 lower plug, If you thing the CHT probes are wired correctly. I've seen several cracked ceramics too. 

 Response to PTK, not Mr. Gibbs.

-Matt 

Geez, last name?  wanna make a guy feel old or what

A failed plug will increase egt on that cylinder when mags are both.  if you select the bad plug mag the egt will essentially zero and the vibration will get your attention Right Now.  been there, done that

[MB65E]

NCIS Gibbs!!

[PTK]

2 hours ago, Cyril Gibb said:

Geez, last name?  wanna make a guy feel old or what

A failed plug will increase egt on that cylinder when mags are both.  if you select the bad plug mag the egt will essentially zero and the vibration will get your attention Right Now.  been there, done that

No vibration beyond the normal roughness due to being lean and on one mag.

Never any vibration any other time.

[PTK]

2 hours ago, Cyril Gibb said:

I'd guess there are 2 separate issues. Cylinder 3 starts dropping when  you lean and recovers when you richen.  If you're LOP at that ff, then the cylinder will cool more than the others if it's a little leaner. Perhaps cylinder 3 injector picked up some fod? What does the gami spread look like?

 

Gami spread <0.1 gph.

Is it conceivable that cyl3 is closer to flaming out first? In other words it's the leanest?

That's my feeling. My reasoning is that it does so on either mag. I think the plug is fine. 

[Cyril Gibb]

17 minutes ago, PTK said:

Gami spread <0.1 gph.

Doesn't make a lot of sense to me if the gami spread is that close and the chts/egt probes are numbered correctly.  When you lean, all the chts go down as expected, but CHT 3 goes down more.  All the chts don't vary much with the mag checks so I doubt it's ignition related.  all the chts then go up in tandem when you enrichen.  logic would suggest uneven chts to be fuel system related.

Time for the hired guns.

[Steve W]

I don't really speak engine monitor. But that sort of looks like a probe problem to me. It looks like it's relating to leaning, and not the actual mag check. Isn't #3 where the factory probe is usually? Maybe it's in a different sort of mount that's causing problems. Maybe a spark plug gasket location that's cooling much faster?

 

Edited July 5, 2017 by Steve W

[PTK]

I went back and checked previous archived traces and it's consistent. Historically cyl 3 has been cooler during lean mag checks. I don't feel anything is out of line. Thank you all! 

Here's another one:

https://savvyanalysis.com/flight/1659931/365d5f00-b89b-4f12-9144-e3b1c5fb0e98

and here is a representative gami spread:

 

[kortopates]

Peter,

Your Top #3 plug is missing and your bottom #3 is in early stages of it. Also your bottom #4 has an excessive rise. Is this significant? I can't say without a gami spread just before the LOP Mag test to see just how LOP the test was done. Any interpretation of the LOP mag test needs to be done in the context of how LOP the test is done since your stressing the ignition system more by the more LOP you go. But whenever I see both plugs of the same cyl showing the signs of missing and very high rises as we see here, I am suspicious of the cylinder being overly lean. For example, your leanest cylinder is going to be the first to start showing signs of missing by going excessively lean. But you may know how much LOP you were running when you ran the test and I'd suggest if you were well excess of 50 LOP not to be concerned but if you were 50 LOP or less then I would address and inspect & clean the plugs; especially checking internal resistance. But since FF was further pulled just before the test from 10 to >8 GPH that makes it pretty hard.

So why the 50 LOP cutoff? Since 50 LOP is the maximum we ever need to be to run at higher power settings LOP, there is no point in performing maintenance that won't do you any good.  But any missing upto 50 LOP is considered premature IMO since its very reasonable to need to run 50F LOP at 75% power, should you so desire.

But given the very high rises, and both plus in #3 showing signs of missing, I'd guess the cyl is overly lean and would repeat the test before relying the test results. Incidentally the excessive rises in EGT is also the cause of the large CHT drop and another clue for the mixture being overly lean.

Also I'd recommend performing the gami spread slower - less than 30 seconds from 11 - 7.5 GPH with your 2 sec sampling rate isn't giving you as accurate results as you can get if performed 2 to 3x slower and be sure to perform the test at WOT to avoid any significant changes in MAP which will also reduce the quality of your data.  It is really hard to do this test well if you are having to manipulate the lever controls on a quadrant style, but if you have vernier controls its very easy. Of course, perform the gami multiple times to ensure you are getting repeatable consistent results. 

For more on interpreting ignition tests see our write up here: https://www.savvyanalysis.com/articles/in-flight-diagnostics 

For more understanding of the EGT rise accompanied by a CHT drop relationship from an ignition issue see ENGINE MONITOR WEBINAR     https://www.youtube.com/watch?v=0SvTESXqidM 1 hr 13 mins

For our guidance on how to best run these tests see http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf

Edited July 6, 2017 by kortopates

[PTK]

6 hours ago, kortopates said:

Peter,

Your Top #3 plug is missing and your bottom #3 is in early stages of it. Also your bottom #4 has an excessive rise. Is this significant? I can't say without a gami spread just before the LOP Mag test to see just how LOP the test was done. Any interpretation of the LOP mag test needs to be done in the context of how LOP the test is done since your stressing the ignition system more by the more LOP you go. But whenever I see both plugs of the same cyl showing the signs of missing and very high rises as we see here, I am suspicious of the cylinder being overly lean. For example, your leanest cylinder is going to be the first to start showing signs of missing by going excessively lean. But you may know how much LOP you were running when you ran the test and I'd suggest if you were well excess of 50 LOP not to be concerned but if you were 50 LOP or less then I would address and inspect & clean the plugs; especially checking internal resistance. But since FF was further pulled just before the test from 10 to >8 GPH that makes it pretty hard.

So why the 50 LOP cutoff? Since 50 LOP is the maximum we ever need to be to run at higher power settings LOP, there is no point in performing maintenance that won't do you any good.  But any missing upto 50 LOP is considered premature IMO since its very reasonable to need to run 50F LOP at 75% power, should you so desire.

But given the very high rises, and both plus in #3 showing signs of missing, I'd guess the cyl is overly lean and would repeat the test before relying the test results. Incidentally the excessive rises in EGT is also the cause of the large CHT drop and another clue for the mixture being overly lean.

Also I'd recommend performing the gami spread slower - less than 30 seconds from 11 - 7.5 GPH with your 2 sec sampling rate isn't giving you as accurate results as you can get if performed 2 to 3x slower and be sure to perform the test at WOT to avoid any significant changes in MAP which will also reduce the quality of your data.  It is really hard to do this test well if you are having to manipulate the lever controls on a quadrant style, but if you have vernier controls its very easy. Of course, perform the gami multiple times to ensure you are getting repeatable consistent results. 

For more on interpreting ignition tests see our write up here: https://www.savvyanalysis.com/articles/in-flight-diagnostics 

For more understanding of the EGT rise accompanied by a CHT drop relationship from an ignition issue see ENGINE MONITOR WEBINAR     https://www.youtube.com/watch?v=0SvTESXqidM 1 hr 13 mins

For our guidance on how to best run these tests see http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf

Paul,

I sincerely thank you for taking the time to share your professional opinion and expertise. I greatly appreciate your suggestions. I will follow your guidance so I may obtain data that will lend itself to more meaningful interpretation. 

If I understand you correctly, and please correct me if I'm wrong, my plan is to first do the gami spread ~3x slower. I do have vernier controls and it's really easy. Then, and from a known LOP value, go right into the lop mag check. I will do this and post data plots.

I was well in excess of 50° lop and suspected cyl3 is too lean. As you say because it's both plugs on cyl3 and being overly lean I'm not concerned. But will verify.

Thank you again Paul.

[carusoam]

Peter,

remember to report the plugs that you are using... If able.

A subtlely failing plug sounds a lot like a champion with its resistance increasing over time.

Best regards,

-a-

[PTK]

6 hours ago, carusoam said:

Peter,

remember to report the plugs that you are using... If able.

A subtlely failing plug sounds a lot like a champion with its resistance increasing over time.

Best regards,

-a-

Excellent point Anthony. I'm running Tempest URHM38E since June 2014. I had resistance issues with the previous champions which I wasn't aware. As far as I could tell they were running fine. But decided to change them out on the recommendation of the A&P as they were getting old. There was some discussion around that time about resistance and the issues Champion was having. So we decided to check the resistance on several of them out of academic interest and curiosity really. I remember almost all of them were very high and a couple were way out of the ball park high!

Here's Norm Howell's article...

http://www.openclip.net/Benchmark/AOALog2011SpringTwoSparks.pdf

[carusoam]

Norm is brilliant...

Thanks for sharing the article.

Best regards,

-a-

[PTK]

On 7/6/2017 at 2:27 PM, kortopates said:

...Also I'd recommend performing the gami spread slower - less than 30 seconds from 11 - 7.5 GPH with your 2 sec sampling rate isn't giving you as accurate results as you can get if performed 2 to 3x slower and be sure to perform the test at WOT to avoid any significant changes in MAP which will also reduce the quality of your data.  It is really hard to do this test well if you are having to manipulate the lever controls on a quadrant style, but if you have vernier controls its very easy. Of course, perform the gami multiple times to ensure you are getting repeatable consistent results...

Here it is Paul. I hope it is better. I did Gami spread real slow taking ~3 min for each swing. Lean mag test was at >50° lop. Looks like cyl3 is the leanest.

https://savvyanalysis.com/flight/1967721/b3d0d497-9b3a-4d78-8737-8a128f5def7b

[kortopates]

Hi Peter ( @PTK )

Indeed your gami sweeps are doing great, we're seeing pretty consistent 0.2 with your #1 & #4 pretty closely tied to richest and your 2 & 3 pretty closely tied to your leanest as well - you'll see the last spread, which is the same one you illustrated above, shows 3 the leanest and 4 richest, but on average that distinction is not clear. But it really doesn't get much better than that!

Good job on the LOP Mag test - your right on target at ~50-60 LOP too. But it is showing some missing in your #3 on the first mag you isolated. Normally I can tell exactly if that is bottom on top, but your timing also appears slightly split causing the first mag to have higher rises across all cyls (i.e. first mag is retarded a bit in relation to the second mag) hiding which is bottom and tops. But I would guess its your top #3, but I could be wrong, plus you are getting a little missing on the other #3 so I would check them both out. Also we're getting a minor amount of early signs of missing in the first mag on #2 & #4 which I would guess to be bottoms - but follow from the first mag you isolated - if you choose to check those 2 plugs too.

If you have the Dual Mag, I'd probably opt to live with it till the next time you have a chance to inspect the mag at annual.   

The 3 spreads follow:

Time: 00:34:00-00:36:18

EGT2 peaked at 9.1   <-- 2 & 3 leanest

EGT3 peaked at 9.1

EGT1 peaked at 8.9   <-- 1 & 4 richest

EGT4 peaked at 8.9

GAMI spread is 0.2

Time: 00:37:00-00:39:16

EGT2 peaked at 9.4

EGT3 peaked at 9.4

EGT4 peaked at 9.4

EGT1 peaked at 9.2

GAMI spread is 0.2

Time: 00:39:52-00:42:24

EGT3 peaked at 8.8

EGT1 peaked at 8.7

EGT2 peaked at 8.7

EGT4 peaked at 8.6

GAMI spread is 0.2

Edited July 9, 2017 by kortopates