Failing exhaust valve in Savvy?

[Matt Ward]

Hey everybody,

Merry Christmas and Happy Holidays!  I just took a nice flight from Denver down to Colorado Springs and back and noticed something in my EGT data that I've not seen before.

The Savvy file is here: https://apps.savvyaviation.com/flights/4599237/f87a4cd4-5142-4d16-9175-0c6a837759a9

According to what I've read, a failing exhaust value will exhibit "A slow, rhythmic EGT oscillation (often on the order of one cycle per minute) is the unique signature of a failing exhaust valve."  The FEVA algorithm wasn't tripped on my flight but it still looks odd.

The part of the flight I'm interested in is from about 0:52 to about 1:08:

During this period I was running LOP at 2400, probably about 21", 9500 feet, 8.6 GPH, TAS of about 147k which is my normal.

Zooming in, you see something like this.  The temperature delta is about +- 10 degrees but it is happening rhythmically on roughly a one minute interval.

 

Anyone better than me at this stuff see anything interesting?

Thanks!

 

[kortopates]

10 degrees isn’t enough magnitude to trip our algorithm. But don’t hesitate to open an analysis ticket and I’ll take a real look next week for you and let you know.


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[gsxrpilot]

• Data logging engine monitor
• Savvy Analysis subscription
• MooneySpace
• @kortopates (Paul K)

That is a powerful combination and one I'm thankful for every single time my Mooney flies. 

An affordable version of a Formula 1 crew.

[PT20J]

2 hours ago, kortopates said:

10 degrees isn’t enough magnitude to trip our algorithm. But don’t hesitate to open an analysis ticket and I’ll take a real look next week for you and let you know.


Sent from my iPhone using Tapatalk

Paul, Curious to know what magnitude EGT swings you usually see with valve issues.

Skip

[Ragsf15e]

It does look interesting, but that egt looks like it’s varying earlier in the flight too.  The sensor isn’t loose or the exhaust pipe vibrating, is it?  It kinda looks like it has some issues from the beginning.

Edited December 26, 2020 by Ragsf15e

[carusoam]

This is the classic saw tooth pattern we see when discussing sticky/ non-rotating valves...

Looking forward to hearing back from Savvy...

Go PK!

PP thoughts only, not a mechanic...  probably enough info to start considering the next steps...

Best regards,

-a-

[kortopates]

3 hours ago, PT20J said:

Paul, Curious to know what magnitude EGT swings you usually see with valve issues.

Skip

Sure Skip,

A sinusoidal oscillation in EGT of frequency .75 cycle(s) per minute with an amplitude of 40º F ± 10º peak-to-peak.

Correlation is high, but not 100%. When we see it we advise borescoping the valve. When caught early enough, we've have had very good results lapping the valve in situ to correct the issue. The trick is to catch it early enough with a hot spot before being burnt. 

Edited December 26, 2020 by kortopates

[Yourpilotincommand]

Definitely looking like the #2 exhaust valve. Time to stick a bore scope in to confirm. I’d expect a cylinder replacement in the near future.

[philiplane]

Borescope of the cylinder is in order. Any available oil analysis results would also be useful, increasing nickel trends indicate valve guide wear.

I have an Insight G4 monitor in my plane, it has an exhaust valve analysis feature built in. You can check it live, no need to send data out.