One EGV indicates 500 degrees or more below the others

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bryanchatham
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One EGV indicates 500 degrees or more below the others

Post by bryanchatham »

Coming back on a cross country, I went to lean the engine and noticed #3 cylinder EGV was about 500 degrees or more below the other cylinders. The plane developed full power on take off, and I didn't have any indications of power loss at cruise. I don't fly this particular plane enough to know its intricacies. There was no squawk on EGT when I picked it up. CHTs all appeared normal. I learned it out to about 8.5 GPH and we were cruising along about 130knots IAS. Oil temp was low in the band, but still in green and it was about -3C out. I continued the flight and assumed, maybe incorrectly, this was just a sensor anomaly. I think had it been CHT, I would have reacted differently if I had a single hot CHT. But it was EGV so I wasn't concerned about since the engine seemed to be running smoothly. Would others have made a different decision? Or are there other items I should have checked? I landed without incident and wrote it up.
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Steve
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Re: One EGV indicates 500 degrees or more below the others

Post by Steve »

Bryan:

The one possible mechanism for the disparity in EGT that would worry me would be the EGT sensor clamp failing, allowing the sensor to back out of the exhaust riser. This would lead to a lower EGT reported by that sensor (the tip of the sensor would be out of the center of the exhaust gas stream). It could also lead to a stream of exhaust gas jetting out of the sensor hole, and impinging on something in the engine compartment. I might have returned and pulled the cowling to take a look at it.
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Soareyes
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Re: One EGV indicates 500 degrees or more below the others

Post by Soareyes »

bryanchatham wrote: Thu Mar 30, 2023 1:12 pm But it was EGV so I wasn't concerned about since the engine seemed to be running smoothly. Would others have made a different decision? Or are there other items I should have checked?
I would worry about a cracked exhaust manifold spewing a jet of 1,500 degree gas at perhaps a fuel line or something. Immediate landing and taking a look under the cowling would be my plan.
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Rich
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Re: One EGV indicates 500 degrees or more below the others

Post by Rich »

Just a non-confrontation question. Most of us refer to Exhaust Gas Temperature as EGT. Is EGV more meaningful somehow?
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Re: One EGV indicates 500 degrees or more below the others

Post by bryanchatham »

Great answers thanks. Not what I was expecting. And thanks for correction — I should be calling it egt not egv.

I will post resolution once I hear back from the club.
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Rich
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Re: One EGV indicates 500 degrees or more below the others

Post by Rich »

These probes do fail. Or perhaps the connector where it joins the harness. This really is the most likely scenario.
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Chris B
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Re: One EGV indicates 500 degrees or more below the others

Post by Chris B »

Rich wrote: Fri Mar 31, 2023 2:28 pm These probes do fail. Or perhaps the connector where it joins the harness. This really is the most likely scenario.
Yes.

I have had to replace two connectors, but so far (~3500 hrs) never had an EGT probe fail.
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Steve
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Re: One EGV indicates 500 degrees or more below the others

Post by Steve »

On the VM1000 the computer will detect a probe or connection failure and indicate on the display. Not sure about the G1000, but would assume the same.
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Re: One EGV indicates 500 degrees or more below the others

Post by dmloftus »

Chris B wrote: Mon Apr 03, 2023 1:21 pm I have had to replace two connectors, but so far (~3500 hrs) never had an EGT probe fail.
What are the symptoms of a bad connector vs a bad probe? I have recently seen my #3 EGT walk up and down more than 50 degrees when running LOP. Usually my EGTs have tracked pretty close, within 10-20 degrees, around 1500 LOP with cylinder temps around 340. Flying to and from Memphis last week, the #3 EGT slowly oscillated up and down to around 1550. I'm trying to decide whether this is a noisy instrumentation issue or whether I'm about to have an exhaust valve problem. Mike Busch's engine book says, "When exhaust valves start to burn and leak in piston aircraft engines, they often produce an oscillation in the cylinder’s EGT that can be used to detect incipient exhaust valve failure. The characteristic signature is subtle: a slow rhythmic EGT oscillation with a period of roughly one cycle per minute and an amplitude of 30 to 50 degrees Fahrenheit..."
EGT Graph 2.jpg
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Rich
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Re: One EGV indicates 500 degrees or more below the others

Post by Rich »

David, that does look like what Mike Busch talks about. Definitely worth a borescope check of #3.
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