Break in factory new cylinders

[Alan Maurer]

Hello Mooney People, Just had good top overhaul for IO550  AFTER 1100 HOURS. Six factory new cylinders nicely done. using straight mineral oil and have put 16 hours on new cylinders. Fliing at 75% power and intermittent very to 65 % power. Enging running very smoothly. Still    number #4 cylinder EGT  runs 100 degrees over others running at 75 percent power  running ROP. Thinking might be bad probe??? What  else would cause one EGT cylinder #4 to run hotter? Now have 16 hours since work was done and plan oil change and analysis and will carefully cut open oil filter. Look for tiny metal sparkles. Oill consumption stable now. Thinking time to go back to AD oil. Would love some opinions....

Thanks

Alan

N913ND Ovation KVNC

[Brandt]

I assume all temps were equal before the cylinder change?  So my first thought would be the probe since that’s easy to swap.  Second thing I’d do is borescope to check the cylinder wall condition and the plugs.  Not a mechanic.  Just spitballing… 

[GeeBee]

Swap probes see if it is the probe or the cylinder.

[Ragsf15e]

Did you put new spark plugs in at the same time? A plug not firing perfectly will cause a higher egt.

[Bolter]

11 hours ago, Alan Maurer said:

Hello Mooney People, Just had good top overhaul for IO550  AFTER 1100 HOURS. Six factory new cylinders nicely done. using straight mineral oil and have put 16 hours on new cylinders. Fliing at 75% power and intermittent very to 65 % power. Enging running very smoothly. Still    number #4 cylinder EGT  runs 100 degrees over others running at 75 percent power  running ROP. Thinking might be bad probe??? What  else would cause one EGT cylinder #4 to run hotter? Now have 16 hours since work was done and plan oil change and analysis and will carefully cut open oil filter. Look for tiny metal sparkles. Oill consumption stable now. Thinking time to go back to AD oil. Would love some opinions....

Thanks

Alan

N913ND Ovation KVNC

You specify EGT but did not comment on CHT.  CHT values are absolute, where EGT is really about relative values, such as degrees from peak or watching a trend on a given cylinder. 

There are things about EGT that can lead to variation between cylinders that is not meaningful.  Simply where the probes were drilled and inserted will give big variation.  In this case, assuming they used the same holes, the tip may not penetrate quite the same distance, tip is bent a little, or the flow from this new cylinder is slightly biased in one direction versus the previous one as it flows during exhaust valve opening.   

[1980Mooney]

11 hours ago, Alan Maurer said:

Hello Mooney People, Just had good top overhaul for IO550  AFTER 1100 HOURS. Six factory new cylinders nicely done. using straight mineral oil and have put 16 hours on new cylinders. Fliing at 75% power and intermittent very to 65 % power. Enging running very smoothly. Still    number #4 cylinder EGT  runs 100 degrees over others running at 75 percent power  running ROP. Thinking might be bad probe??? What  else would cause one EGT cylinder #4 to run hotter? Now have 16 hours since work was done and plan oil change and analysis and will carefully cut open oil filter. Look for tiny metal sparkles. Oill consumption stable now. Thinking time to go back to AD oil. Would love some opinions....

Thanks

Alan

N913ND Ovation KVNC

 

4 minutes ago, Bolter said:

You specify EGT but did not comment on CHT.  CHT values are absolute, where EGT is really about relative values, such as degrees from peak or watching a trend on a given cylinder. 

There are things about EGT that can lead to variation between cylinders that is not meaningful.  Simply where the probes were drilled and inserted will give big variation.  In this case, assuming they used the same holes, the tip may not penetrate quite the same distance, tip is bent a little, or the flow from this new cylinder is slightly biased in one direction versus the previous one as it flows during exhaust valve opening.   

Good point about CHT.

Also on the list of "look for the obvious" first - with new jugs, the fuel injectors were removed from the old jugs and reinstalled on the new.  Something as simple as dislodged debris could be reducing fuel to #4 causing it to run lean and hot.  And - are you sure that they got the injectors installed on the correct cylinders?   Shops do make mistakes...perhaps more nowadays.

[Alan Maurer]

Hello Mooney People, After 16 hours with new cylinders , changed the oil and went back to AD oil. Switched the $4 EGT probe and will see if the #5  cylinder now runs hotter. All the CHT probes are nicely lined up and did not change any plugs....and will check!

Alan

[DC_Brasil]

6 hours ago, Bolter said:

 

There are things about EGT that can lead to variation between cylinders that is not meaningful.  Simply where the probes were drilled and inserted will give big variation. 

EGT by itself means very little. Variations among cylinders are common and no reason to worry if CHTs are within a reasonable proximity and the engine is running smoothly. 

Watch these two videos by Mike Busch from Savvy Aviation. They will shed a great deal of light for you.

 

 

 

[AspiringOwner]

8 hours ago, 1980Mooney said:

 

Good point about CHT.

Also on the list of "look for the obvious" first - with new jugs, the fuel injectors were removed from the old jugs and reinstalled on the new.  Something as simple as dislodged debris could be reducing fuel to #4 causing it to run lean and hot.  And - are you sure that they got the injectors installed on the correct cylinders?   Shops do make mistakes...perhaps more nowadays.

Injector would have been my first guess, too

[DC_Brasil]

8 hours ago, AspiringOwner said:

Injector would have been my first guess, too

Why?

The OP hasn't shared his actual engine monitor data. EGT is affected by many factors and its absolute value or even it's spread across cylinders means very little. 

If the engine is working well and smooth, CHTs look fine, I'd be extremely reluctant to attack the plane with tools. First order of business should be to analyze thoroughly the engine data. It will give way more insight.