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Spike in CHT #1 after annual.


DaveMC
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I swear I really don't like surprises.

 

My aircraft just came out of annual September 1, 2021. During the annual #1 cylinder compression was 12. It was determined that the cylinder needed to be replaced. it was. after annual I flew the aircraft for an hour in Caldwell, ID (EUL) 17 September 2021. While #1 was slightly hotter than the rest it was not way out. I then flew the aircraft from EUL to FTT with a stop at APA for fuel. Again no crazy numbers. Today I had a flight planned for KFTT to 2R4. Run up was uneventful, takeoff roll seemed a little slow but I was full of fuel and near gross wt. initial climb out seemed ok until I saw # 1 way out of sync with the others. I immediately reduced power and turned back. on leveling off at 2500 and reducing power it seemed as if the engine was just a tad rough.  Landing was uneventful.  I downloaded the JPI 900 and will attach.  I also have a few marginally good pics of the cylinder which I will post.  I have uploaded to Savvy aviation.  Engine is 100hrs past TBO and all oil analysis had been fantastic. oil changed every 25hrs and running CamGuard

I will post the flight data in order of flights.  With the last one in the series being today.  For a fraction of a second I thought to myself.... "come on Dave it might smooth out"  then I said to myself " don't be a dumbass" as I was turning around. :)

 

Would love thoughts from the group.


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Third Flight.PNG

High TEMPS on #1.PNG

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Follow up from Savvy for the gearheads in  the group

 

Hi David,
This is typically one of two issues stemming from mixture or spark - either a partially clogged injector or only 1 plug firing. Given that EGT1 is 300F high, which far exceeds what we typically see for a bad plug, and that the rise in CHT also points to mixture, this strong evidence for partially clogged injector causing an overly lean mixture.

This isn't that unusual after recent cylinder work where the injector was R&R'd. Unfortunately just  placing the injector back into the cylinder can nick the o-ring or even some dirt can be introduced re-attaching the fuel line. It even happens a lot from cleaning the injectors.
 
We'd recommend starting with the injector, checking for any debris and cleaning and replacing o-rings.

After doing so, suggest holding brakes on runway ,or area where ramp is clean of FOD that could be sucked up by prop, and going to full power and giving it a couple seconds to see EGT come up, then only takeoff if you don't see EGT1 escalate above the pack which will all be under 1500F and more likely in the  low to mid 1400F's.

Unrelated to this, also recommend resetting your data sampling rate 1 sec and then flying the Savvy Test profile.

Let us know what you find.

Paul Kortopates
A&P/IA, CFI-II

P.s. don't hesitate to flag a ticket like this as Urgent.

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Dave you have done incredibly well…

No dumbass award being issued tonight.

Expect the fuel injector for Cylinder #1 needs to be looked at… probably cleaned of whatever is in there… catch whatever falls out of it. Get pics and post that too…  you want to know the source, so there won’t be any more…

About the possibility of a bad plug… sure, but that should show up during the run-up…. How precise is your run-up?  Quick and dirty… or slow and precise enough to know if a single spark plug out of 12 is mis behaving…?

 

+1 for speeding up the data rate…

+1 for slowing down the Run-up to actually see all that can be seen… all plugs, and mag timing issues are found here…

 

The letter signed by that guy… Paul Kortopates is worth its weight in gold… :)

Looks like you got your money’s worth from your Savvy membership…


Thanks for sharing the details…

Best regards,

-a-

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Back to the original issue…

Did the mechanic discuss what caused the drop in compression?

It is hard to see the exhaust valve from this pic… but it doesn’t look horrible…

Some exhaust valves are responsible for loss of compression…

They stop rotating, and cooling gets uneven, then hot spots near the edge show up… 

Signatures of sticky valve syndrome appear in the EGT graphs…

After that the valves don’t seal very well…

PP discussion only, not a mechanic…

Best regards,

-a-

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6 hours ago, carusoam said:

Back to the original issue…

Did the mechanic discuss what caused the drop in compression?

How precise is your run-up?  Quick and dirty… or slow and precise enough to know if a single spark plug out of 12 is mis behaving…?

Thank you for the response. Several things I will change after this event.

1)  A slower more detailed run up.   The data shows' a real big drop on the right mag however I did not see that on instrumentation.  I need to still figure that out. Also the EGT/CHT separation started at full power.

2)  Pay more attention to the EGT/CHT monitor EARLIER in my takeoff roll.  I believe that I could have see the disparity early enough in the take off roll to abort.

As far as the reason for compression loss the mechanic felt that it was the cylinder walls not valves. Which to me seems very bad to me. 

 

 

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Update #2.  injector pulled after a ground run reproduced the same issue.... no debris (i watched directly)

 

top spark plug OK. 

small amount of fluid seen pooling in the dependent portion of the cylinder on visual inspection through the spark plug hole presumed oil.(not a bore scope).

 

More to follow  

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Cylinders are born with a nicely honed cross-hatch pattern on the walls…

As they wear… often the cross-hatch pattern gets removed and leaves a shiny surface in its place…

A cylinder OH will rehone the barrel…. As one of the steps…

The pattern has something to do with oil staying around for lubrication…

If the pattern is gone, the lubrication probably became sub-optimal…

Cylinders can be a cost of doing business…  a trade for higher speeds can be a set of cylinders at the halfway point… (or more, when flying and using the flaming dragon mode…)

Thanks for sharing the details…

Best regards,

-a-

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11 hours ago, carusoam said:

If the pattern is gone, the lubrication probably became sub-optimal Cylinders can be a cost of doing business…  a trade for higher speeds can be a set of cylinders at the halfway point… (or more, when flying and using the flaming dragon mode…)

 

Thanks "C"

 

the cylinder in question #1 is the cylinder that we just overhauled 2nd to low compressions at annual.  with the limited view one could see the crosshatching.  It was the small pooling of liquid presumable oil that was the head scratcher. 

 

more to come  

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Dave,

can we assume you have a Bravo…. With the wet heads?

Bravos use oil to supply some cooling to the head…

If you have oil entering the cylinder…

Could be a broken oil ring at the bottom of the piston’s stack of rings… or possibly a valve stem allowing leaking at the head…(?)

 

Lets invite @M20Doc to stop by this thread… (cylinder challenges, M20M… oil pool)

Best regards,

-a-

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7 hours ago, carusoam said:

can we assume you have a Bravo…. With the wet heads?

I do.  and $5000 worth of oil hoses to prove it  :)  ( had to change those out on my first annual after ownership) 

 will ask the mechanic if he borescoped and got a good look at the "pooling"  I wasn't impressed when I saw it but I'm not an A and P. 

on the good news side he reports that after soaking the injector and blowing it out with hopps the #1 is no longer hot on ground runup.  we are going to check the "induction tubes"???.  while the lower plug needed cleaning both plugs looked and tested out fine.

 

I am having him change out the cork valve cover gaskets for silicone as well a s the gasket for the cover where the vacuum pump used to live.

Thanks again for the hlep

 

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2 hours ago, DaveMC said:

I do.  and $5000 worth of oil hoses to prove it  :)  ( had to change those out on my first annual after ownership) 

 will ask the mechanic if he borescoped and got a good look at the "pooling"  I wasn't impressed when I saw it but I'm not an A and P. 

on the good news side he reports that after soaking the injector and blowing it out with hopps the #1 is no longer hot on ground runup.  we are going to check the "induction tubes"???.  while the lower plug needed cleaning both plugs looked and tested out fine.

 

I am having him change out the cork valve cover gaskets for silicone as well a s the gasket for the cover where the vacuum pump used to live.

Thanks again for the hlep

 

You will like your TIO-540-AF1B engine much more when it has fine wire spark plugs. I use Tempest. A lot of leaded fuel runs through this engine and the massive wire plugs get lead balls stuck in by the electrode. I thought I needed a new mag on run-up. It turns out it was lead stuck in  by the electrode. A few weeks later I put in fine wire plugs and it runs much smoother.

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On 10/14/2021 at 6:38 AM, LANCECASPER said:

You will like your TIO-540-AF1B engine much more when it has fine wire spark plugs. I use Tempest. A lot of leaded fuel runs through this engine and the massive wire plugs get lead balls stuck in by the electrode. I thought I needed a new mag on run-up. It turns out it was lead stuck in  by the electrode. A few weeks later I put in fine wire plugs and it runs much smoother.

Interesting. I'm going to look into fine wire spark plugs when I get my plane back into Tucson. 

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