Cylinder Temperature Issue

[gsxrpilot]

You're only about 40 Mooney minutes from Dalton, GA. I'd go have Joey Cole give you a second opinion on that cylinder work.

[StevenL757]

Just now, Brandontwalker said:

Oil consumption is up and I am seeing oil from the breather. This seems to confirm a compression issue. Before, I was seeing 11 hours per quart. Now I am at 6-7 hours per quart. Oil changes have routinely been at, or before, 50 hours.

Got it.

Going forward, suggest you shift your oil and filter changes to 25-30 hour intervals.  Closer to 25 hours if your flights are short (less than 2 hours each).  30-hour intervals for longer-range trips (>2 hours, give or take).  I don't care if the Lycoming manual says 50 hours is ok...that's just a guideline.  25 to 30 hours and your engine will thank you over the long term.

[Brandontwalker]

The saga continues. Took it in for a second opinion. Took bonafide compressions. Cylinder 3 (the one overheating) is 80/80. However, you could see some blow by in the form of gasses from the breather tube. He pulled and cleaned the injector for good measure. I cowled it up and went for a ride. The results... the highest temperature I have seen to date on number 3. 432 in level cruise. I am stumped. A recap of what has been done to date:

1) swap cht probe

2) move cht probe with wiring intact to assure there is no issue with the JPI leads

3) change spark plugs

4) clean fuel injector/sleeve

5) clean fuel line from diverted to injector

6) soak cylinder in MMO

7) bore scope (no scratches on walls and valves look good)

8) compression test (80/80). It was 79/80 at last annual

At this point, a low compression reading may have been for the best. 
 

[Brandontwalker]

Just now, Brandontwalker said:

The saga continues. Took it in for a second opinion. Took bonafide compressions. Cylinder 3 (the one overheating) is 80/80. However, you could see some blow by in the form of gasses from the breather tube. He pulled and cleaned the injector for good measure. I cowled it up and went for a ride. The results... the highest temperature I have seen to date on number 3. 432 in level cruise. I am stumped. A recap of what has been done to date:

1) swap cht probe

2) move cht probe with wiring intact to assure there is no issue with the JPI leads

3) change spark plugs

4) clean fuel injector/sleeve

5) clean fuel line from diverted to injector

6) soak cylinder in MMO

7) bore scope (no scratches on walls and valves look good)

8) compression test (80/80). It was 79/80 at last annual

At this point, a low compression reading may have been for the best. 
 

Also, run ups are good, but could this somehow be related to the magneto or timing? Nothing has been changed, but it is an item which has not been checked yet. 

[kmyfm20s]

35 minutes ago, Brandontwalker said:

Also, run ups are good, but could this somehow be related to the magneto or timing? Nothing has been changed, but it is an item which has not been checked yet. 

Do an in air magneto check and it should be pretty apparent if one of the mags is causing the problem. 

[EricJ]

Has nobody looked at your baffle gaskets and baffling?    Put a bright light in the oil service hatch behind the baffling and look in from the air inlet by the prop.   You should not very much or any light.   If there are gaps, fix those.   Might be worth checking the intercylinder baffle that sits under and between cyls 1 and 3, and just generally all the baffling around them.   Also the cowl flap travel, etc., on that side.

  

 

[carusoam]

CHTs are the result of....

• heat generated inside the cylinder
• minus 
• heat removed from the cooling fins

Looking at the EGTs shows that the cylinders are pretty much getting similar heat generated inside....

Looking at the CHTs shows one cylinder being much warmer than the others...

Why is the heat not being removed on that one like the other three....

See Eric’s explanation regarding cooling improvements above... 

For more detail... down/up load the JPI data using savvy.... the screen shot only shows a moment in time... which is about 1/1000 of the valuable data that is collected by the monitor...

PP thoughts only not a mechanic...

Best regards,

-a-

[Brandontwalker]

22 minutes ago, EricJ said:

Has nobody looked at your baffle gaskets and baffling?    Put a bright light in the oil service hatch behind the baffling and look in from the air inlet by the prop.   You should not very much or any light.   If there are gaps, fix those.   Might be worth checking the intercylinder baffle that sits under and between cyls 1 and 3, and just generally all the baffling around them.   Also the cowl flap travel, etc., on that side.

  

 

Forgot to note that the baffling is nearly new and in extremely good condition. 

[Brandontwalker]

12 minutes ago, carusoam said:

CHTs are the result of....

• heat generated inside the cylinder
• minus 
• heat removed from the cooling fins

Looking at the EGTs shows that the cylinders are pretty much getting similar heat generated inside....

Looking at the CHTs shows one cylinder being much warmer than the others...

Why is the heat not being removed on that one like the other three....

See Eric’s explanation regarding cooling improvements above... 

For more detail... down/up load the JPI data using savvy.... the screen shot only shows a moment in time... which is about 1/1000 of the valuable data that is collected by the monitor...

PP thoughts only not a mechanic...

Best regards,

-a-

I will pull the JPI data and upload it this weekend. Good suggestion. 

[EricJ]

Just now, Brandontwalker said:

Forgot to note that the baffling is nearly new and in extremely good condition. 

That doesn't mean it ain't leaking.   Installations often need adjustment.   The flashlight test is easy to do.

[Brandontwalker]

2 hours ago, kmyfm20s said:

Do an in air magneto check and it should be pretty apparent if one of the mags is causing the problem. 

Not sure where my earlier reply went. In flight mag check was done yesterday and is normal. 

[M20S Driver]

I am not sure if this was discussed or relevant but it may be worth looking at.  The issues described by Brandon could be a mild version of what my friend was dealing with.  Ultra sonic cleaning of the flow divider solved the fuel flow problem. 

 

[Brandontwalker]

59 minutes ago, M20S Driver said:

I am not sure if this was discussed or relevant but it may be worth looking at.  The issues described by Brandon could be a mild version of what my friend was dealing with.  Ultra sonic cleaning of the flow divider solved the fuel flow problem. 

 

Thank you. The divider is actually next on the list to open and inspect. Mine is not affected by the SB though. 

[EricJ]

Just now, Brandontwalker said:

Thank you. The divider is actually next on the list to open and inspect. Mine is not affected by the SB though. 

If it were a fuel issue it would be expected that the EGT on that cyl would be high, which it doesn't seem to be according to the monitor pic you posted.

[carusoam]

Brandon,

If able...

Take a bunch of pics of the fuel divider while you are in there...

They don’t get mentioned often enough... 

Best regards,

-a-

[M20S Driver]

1 hour ago, Brandontwalker said:

Thank you. The divider is actually next on the list to open and inspect. Mine is not affected by the SB though. 

sounds good.  I suggest to do the ultrasonic clean anyway since visually nothing was seen in the case I mentioned.  Some areas are not easily accessible.

Eric has a good point about EGT change or lack of it.  In my friend's case, which was much more extreme, CHT moved twice as fast as EGT on the JPI data.

[Brandontwalker]

On 5/8/2020 at 3:50 PM, carusoam said:

CHTs are the result of....

• heat generated inside the cylinder
• minus 
• heat removed from the cooling fins

Looking at the EGTs shows that the cylinders are pretty much getting similar heat generated inside....

Looking at the CHTs shows one cylinder being much warmer than the others...

Why is the heat not being removed on that one like the other three....

See Eric’s explanation regarding cooling improvements above... 

For more detail... down/up load the JPI data using savvy.... the screen shot only shows a moment in time... which is about 1/1000 of the valuable data that is collected by the monitor...

PP thoughts only not a mechanic...

Best regards,

-a-

After more testing, I am still in the same spot.  JPI data from the last flight is below.  As for now, I have 3 mechanics from 3 separate shops scratching their heads.  It is never easy...

https://apps.savvyaviation.com/flights/3934161/18d49b98-c5ea-40f8-81c4-8d87f23d0d1f

[carusoam]

Not the same spot....

You have uploaded data... and we can see more...

You have something that is related to the cooling of that one cylinder... and it changes in flight....

See the pic of your data below... The CHT3 is higher than the other three... where I put a line at 7:30... you can see the #3 temp begin to rise, peak, then come back down....

Is something loose under the cowl allowing for this?

I didn’t see any changes in EGT, or MP, related to this change in CHT...

I added a chart of rpm and FF changes to show they probably aren’t related to this odd CHT behavior...

PP thoughts only, not a mechanic...

-a-

[Brandontwalker]

16 minutes ago, carusoam said:

Not the same spot....

You have uploaded data... and we can see more...

You have something that is related to the cooling of that one cylinder... and it changes in flight....

See the pic of your data below... The CHT3 is higher than the other three... where I put a line at 7:30... you can see the #3 temp begin to rise, peak, then come back down....

Is something loose under the cowl allowing for this?

I didn’t see any changes in EGT, or MP, related to this change in CHT...

I added a chart of rpm and FF changes to show they probably aren’t related to this odd CHT behavior...

PP thoughts only, not a mechanic...

-a-

In all of the digging, I have not seen anything loose under the cowl.  I assume it is possible, but, for what it is worth, the temperature issue is apparent even with the cowl off completely.  I have attached another couple of logs below.  The first log was a relatively short flight and you can see the temperature spike at the end.  The other is a ground run without the cowl off the airplane.  The only reason for the cowl off log is to note how much faster cylinder 3 temp rises than the others.

https://apps.savvyaviation.com/flights/3934156/7a33920c-c462-45ea-bb59-ecc9648bd722

https://apps.savvyaviation.com/flights/3934158/b5d96250-4d62-4106-879f-e684285bfcfc

 

[carusoam]

First graph show CHT1 going awry...? (Hotter than the rest...)  short flight

Prior graphs showed CHT3 getting uniquely hot...  

 

1&3 are on the same side of the engine... (pilot side for Lycoming?)

With the cowl off... things are warming up relatively uniformly the difference in CHTs is relatively small...

 

Cowled up and flying... the odd man out is about 50 degrees above the others... and changes mid flight... and is a different man on different flights...

Still looks like a cooling challenge... looking for loose baffling (rubber and aluminum) or those sheet metal pieces between cylinders... anything that can allow airflow away from the cylinders, or block flow...

PP thoughts only... not a mechanic...

Might be a good idea / worth it... to have Savvy look at the graphs...

Or go through a chain of your flights to see what cylinder does this when...  find out when this behavior started...

Best regards,

-a-

 

[carusoam]

There is something really odd about pulling the MP and FF back and the CHT rising...

Note the EGT1 not playing with the others...

-a-

 

[Brandontwalker]

24 minutes ago, carusoam said:

First graph show CHT1 going awry...? (Hotter than the rest...)  short flight

Prior graphs showed CHT3 getting uniquely hot...  

 

1&3 are on the same side of the engine... (pilot side for Lycoming?)

With the cowl off... things are warming up relatively uniformly the difference in CHTs is relatively small...

 

Cowled up and flying... the odd man out is about 50 degrees above the others... and changes mid flight... and is a different man on different flights...

Still looks like a cooling challenge... looking for loose baffling (rubber and aluminum) or those sheet metal pieces between cylinders... anything that can allow airflow away from the cylinders, or block flow...

PP thoughts only... not a mechanic...

Might be a good idea / worth it... to have Savvy look at the graphs...

Or go through a chain of your flights to see what cylinder does this when...  find out when this behavior started...

Best regards,

-a-

 

I feel like a knucklehead.  I forgot to mention that, I swapped the probe from cylinder 1 to 3 on that flight to test the JPI sensor/harness.  Cylinder 1 on the readout is actually cylinder 3...

[bfreelove]

This looks like just an airflow issue to me.  One key clue is that the CHT on 3 rises when the MAP is reduced (assuming the airplane is slowing down at this point).  There are 2 critical areas to look at closely in my experience.  First the rear fins along the back baffle.  There is almost no fin depth there and if the baffle is too tight it cause a very high local pressure drop and reduces the flow considerably, right in the spot where it is most needed.  This is a common issue with Lycoming cylinder's 2 (front) and 3 (back).  Here's a good discussion about it and fixes from the Vans crowd:

http://www.vansairforce.com/community/showthread.php?t=37835

The next place to check is the lower inter-cylinder baffles, and rear cylinder "wrap".  The size of the lower opening formed by these two components can make a big difference, and there is a sweet spot. Too large and it won't pull enough air around the head and cool the bottom (where the probe is), too small and it will cause too much pressure drop on that cylinder and not get enough flow compared to the others.  Check to make sure it looks even with the others.  There's a formula based on average cylinder head fin depth that gives you the proper size for the opening.  I think it's something 1.25 inches for a Lycoming head, but would have to look it up again to verify.  The factory inter-cylinder baffles match this opening exactly if evenly spaced on a 6 cylinder.  The front and rear wraps are always up to the manufacturer so sometimes you'll see issues there (this is one half of the classic issue for cylinder no.5 on the Ovation)

Also check very carefully for any gaps, leaks etc.  It's amazing how these can add up.  I spent a few days tweaking the baffles on my Mooney when I got it and lowered the CHTs by 30 degrees F on average.  The balance also got better as the leaks went away.  

[EricJ]

I think all signs point to baffling/air flow.    The flashlight test is simple and easy and often revealing.    Even if that looks good, check the intercylinder baffles underneath,  cowl flap gaps, carefully check the condition of the front baffling around the alternator, ram inlet, etc.

[Brandontwalker]

Another Saturday...another day of testing.  Today was spent looking over baffling.  The top baffling looks great and there are no signs of light entering when a flashlight is dropped in the oil access.  However, the baffling on the bottom is suspect.  I have attached a video, but I noted that the baffling on the bottom of cylinder 3 was pulled tight against the fins.  Interestingly, the bottom baffling on cylinders 1 and 3 are connected with safety wire.  I loosened the safety wire to create a larger gap on cylinder 3 and took a flight.  Initially, everything looked good.  However, toward the end of the flight, there was a spike in temperature on cylinder 3.  The spike in temperature just seems odd to me.  Because it hit 435, I pulled cowl flaps half open and was able to cool the cylinder down. In the video you can see that if more air is forced through cylinder 1, cylinder 3 would be pulled closed.  Could this be happening in flight?  If so, then why only the one spike in temperature?  More logs are also attached below.

https://apps.savvyaviation.com/flights/3941952/28d82841-961b-4410-8362-f9d4371f3741