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  #1  
Old 03-22-2020, 06:08 AM
Dayz Dayz is offline
 
Join Date: Dec 2016
Location: Toronto, ON.
Posts: 36
Default Cylinder 1 EGT and CHT rise and fluctuate

Guys,
I believe we have an issue with our #1. Today at runup our CHT and EGT went up high, faster than the other 3, engine ran not perfectly ( there was a miss if you listened properly).

Everything seemed to stabilize after but stayed higher the whole flight than usual.

Sensors were acting as if they were going bad, giving all sorts of random data?s. But in this case, the miss, and the fact that CHT and EGT were giving random numbers at runup is puzzling me. I pulled the data and will post it if I can figure out how.

I was thinking of pre ignition? But why, I was full rick at idle. Maybe pieces of hot carbon stuck on a valve that would preignite?

Let me know. We need to find this issue.
Thanks
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  #2  
Old 03-22-2020, 08:38 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 6,735
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That is a tough one. Struggling to come up with a scenario that would raise both, while causing misses. Pre ignition seems pretty unlikely at runup RPMs with a cold engine in cool weather. Detonation also less likely with a cold engine in cool weather. While I have never observed detonation in an engine with EGT sensors, I would expect that CHT would rise rapidly and speculate that EGT would go down or stay the same. I can't think of a reason that detonation would cause a rapid rise in EGT, unless the combustion didn't fully burn the mixture and it was completing it's burn in the exhaust. I just don't know how likely or possible that is.

Detonation is more of an explosion than a contolled burn. It imparts a great deal of heat into the cylinder due to this, but the burn is shorter and less complete and therefore speculate that it would not create elevated EGT readings. Again, have no real experience with EGT data, so just speculation. Most things that raise CHT above normal, reduce EGT from normal, at least when dealing with large swings.

My experience with detonation has always been under haevy load conditions, like high MAP. There may be some slight roughness, but misses are not common, in my experience. I just can't see how someone could get pre-ignition at 1800 RPM on a cold engine, although I am sure it is possible.

I would definitely start the troubleshooting process with the sensors first.

Larry
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Last edited by lr172 : 03-22-2020 at 08:57 AM.
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  #3  
Old 03-22-2020, 10:32 AM
mahlon_r mahlon_r is offline
 
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Posts: 1,060
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Leaky exhaust valve? Partially plugged fuel injector with floating type debris if it's an IO engine?
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  #4  
Old 03-22-2020, 01:10 PM
Dayz Dayz is offline
 
Join Date: Dec 2016
Location: Toronto, ON.
Posts: 36
Default

Guys,
Here is just after sunup and the first few minutes of test flight. Could it be a little drop of the "Champion Graphite Anti Seize" that would have been too low on the thread? I am puzzle. As you can see, it got better and better.
Thanks Again



Last edited by Dayz : 03-22-2020 at 01:17 PM.
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  #5  
Old 03-22-2020, 01:20 PM
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Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
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Wild thought here-----any possibility the wires from the CHT and EGT have rubbed together and worn through the coverings-----shorted together???

I had originally thought of an intake leak, but after looking at the graphs, not what I would expect from an intake leak.
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  #6  
Old 03-22-2020, 01:56 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by Dayz View Post
Guys,
Here is just after sunup and the first few minutes of test flight. Could it be a little drop of the "Champion Graphite Anti Seize" that would have been too low on the thread? I am puzzle. As you can see, it got better and better.
Thanks Again



That is a sensor / instrument issue. CHT cannot rise 50 then fall 100* in .5 seconds. assuming those numbers are seconds and not minutes. Note that both EGT and CHT are RAPIDLY oscillating. The actual temps can't realisticly change that fast. The continually higher oscillation rate of #1 vs the others helps to confirm that diagnosis.

EDIT: I now see they are minutes. However, you are still showing a 100* CHT reduction followed by a 100* increase in the neighborhood of 10-15 seconds. That just isn't possible, regardless of what is happening inside the cylinder.

Larry
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Last edited by lr172 : 03-22-2020 at 02:08 PM.
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  #7  
Old 03-22-2020, 02:05 PM
Don E Don E is offline
 
Join Date: Aug 2016
Location: West Chester, PA
Posts: 133
Default Check for proximity to spark plug leads...

Could be getting voltage bleeding in from a spark plug cable, especially electronic ignition, if these wires are bundled with or too close to one. That could also possibly cause a miss.
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  #8  
Old 03-22-2020, 09:06 PM
Dayz Dayz is offline
 
Join Date: Dec 2016
Location: Toronto, ON.
Posts: 36
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It is an O-360 A1A
No electronic ignition. I will check wires, perhaps both sensors went at the same time.
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  #9  
Old 03-23-2020, 10:03 AM
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walkman walkman is offline
 
Join Date: Oct 2011
Location: Atlanta
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Quote:
Originally Posted by Dayz View Post
"Champion Graphite Anti Seize"
That stuff is horrible. Use a heavy copper based anti-seize instead!

Switched over 20 years ago, never a problem, never a difficult plug.
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  #10  
Old 03-23-2020, 06:20 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 961
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I had the exact same signature -- turned out to be a bad probe. Reterminate the wires just as a sanity check before spending $$$ tho.

Cheers!

B
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