Engine analysis diagnosis.

[johncuyle]

Just when my plane seems to be fine, I am seeing a new issue on my engine traces.  Since you can't tell in flight, I'm guessing EGT 6 probe has failed, or a bad connection (recent install, probably within the time range a weak probe would likely die early) but the other thread has me wondering if I've actually got a misfire.  I will admit that I did not do a run-up for the other couple flights because the plane was never really stopped long enough to cool off and I'm not in the habit of doing additional run ups if I just landed a few minutes ago and it was flying fine when I landed (it's how I was trained), though this definitely has me reconsidering that habit.

Problem begins about 32 minutes into the first trace and starts off small (at the time of a terrible approach that resulted in a relatively early go around.)  It gets worse between 32 and 25 minutes and goes completely haywire after 39:45.

https://www.savvyanalysis.com/flight/3214870/d3b6b0ff-757a-4131-8308-1414f99849b4

Other two hops before I got it home and noticed something was amiss after downloading the traces:

https://www.savvyanalysis.com/flight/3214871/cd747c7e-110f-48c6-9ce5-a058d4caba89

https://www.savvyanalysis.com/flight/3214872/6534ad16-2016-4738-b7a0-f184b6606c1b

Again, the engine seems to run just fine.

[DXB]

8 minutes ago, johncuyle said:

Just when my plane seems to be fine, I am seeing a new issue on my engine traces.  Since you can't tell in flight, I'm guessing EGT 6 probe has failed, or a bad connection (recent install, probably within the time range a weak probe would likely die early) but the other thread has me wondering if I've actually got a misfire.  I will admit that I did not do a run-up for the other couple flights because the plane was never really stopped long enough to cool off and I'm not in the habit of doing additional run ups if I just landed a few minutes ago and it was flying fine when I landed (it's how I was trained), though this definitely has me reconsidering that habit.

Problem begins about 32 minutes into the first trace and starts off small (at the time of a terrible approach that resulted in a relatively early go around.)  It gets worse between 32 and 25 minutes and goes completely haywire after 39:45.

https://www.savvyanalysis.com/flight/3214870/d3b6b0ff-757a-4131-8308-1414f99849b4

Other two hops before I got it home and noticed something was amiss after downloading the traces:

https://www.savvyanalysis.com/flight/3214871/cd747c7e-110f-48c6-9ce5-a058d4caba89

https://www.savvyanalysis.com/flight/3214872/6534ad16-2016-4738-b7a0-f184b6606c1b

Again, the engine seems to run just fine.

I can't imagine an ignition problem that would produce that appearance.  That's gotta be the probe or proximal to it in the monitor system I would think.  EGT probes have a finite life.  When EGT probes on my JPI have misbehaved, retightening their contacts with the harness and coating with Stabilant 22 has been effective so far. Worth a try before replacing.  Also could swap probes between exhaust stacks to help localize.

[carusoam]

Looks like vibration might be causing some of the funky data...

when looking at the graphs, include rpm and FF to see what else may be goin on each time the EGT and CHTs get funky...

I don’t have much EI MVP experience... but it might be a grounding issue, like a loose ground...

We might have an EI guy around here... @oregon87 Oregon might know some tech service guys inside EI...

Best regards,

-a-

[johncuyle]

12 hours ago, carusoam said:

Looks like vibration might be causing some of the funky data...

when looking at the graphs, include rpm and FF to see what else may be goin on each time the EGT and CHTs get funky...

I don’t have much EI MVP experience... but it might be a grounding issue, like a loose ground...

We might have an EI guy around here... @oregon87 Oregon might know some tech service guys inside EI...

Best regards,

-a-

It's not actually an MVP, it's a CGR.  Same probes, though.  Part of the reason I suspected it is just the EGT probe is that CHT seems totally reasonable.  6 is the left front cylinder and should generally be the best cooled of them, so seeing its CHT come down more and more quickly on power reduction isn't surprising or unusual.  Seeing EGT bouncing wildly around anywhere between 1100 and 1400 in cruise is definitely weird.  It might be running slightly cooler overall than usual on that last trace, though, which might indicate a misfire.

[kortopates]

45 minutes ago, johncuyle said:

It's not actually an MVP, it's a CGR.  Same probes, though.  Part of the reason I suspected it is just the EGT probe is that CHT seems totally reasonable.  6 is the left front cylinder and should generally be the best cooled of them, so seeing its CHT come down more and more quickly on power reduction isn't surprising or unusual.  Seeing EGT bouncing wildly around anywhere between 1100 and 1400 in cruise is definitely weird.  It might be running slightly cooler overall than usual on that last trace, though, which might indicate a misfire.

Dev @DXB was right on target. Its possible your EGT probe connection is beginning to fail where the wires come out of the probe - they break down here over time. But its more likely its just a loose connection since your symptom initially is only occurring on the ground at idle when things are shaking a bit more. So check that first as well as look for any chaffed wires in the harness as it goes back to the firewall. But most likely the connection between the probe and harness is just loose, so try that first.

[Igor_U]

I recently have similar issue with EI EGT probe on my CGR30.

EGT1 was lower then others... reason was that actual sensing element with wires got loose from outer jacket/shield. It is swaged in it (I think) and got loose when probe was almost new but was running good for more then couple of years. Recently, I had to remove it to replace intake O-ring and it completely fell apart. Since then, EGT was some 200+ degrees lower then it should be. New probe solve the issue.

[oregon87]

One really simple test is to swap the probe with an adjacent cylinder.  If the erratic temperature follows the probe, the probe should be replaced.  Very often, in swapping cylinders, you're re-tightening the connectors and that alone can solve and erratic indication.  If the problem stays with the cylinder, obviously further investigation will be required.  

Edited June 13, 2019 by oregon87