Baffling problems?

[NicoN]

Good evening!

We have a 1980 M20K and are experiencing quite high oil temperature and high CHT #4.

Oil temperature is most of the time between 205 and 215 - which is still in green arc but Savvy says, it's higher than the majority of the fleet.

Also #4 tends to go as high as 410. All other cyls have normally CHTs below 380.

On our last 50h maintenance, the mechanic and I removed the upper cowling and suspected that the baffling on the pilot's side was at least partially folded back.

A did not assist him re-assembling the cowling, so I am not sure that the baffling was correctly folded forward at that point.

 

Nevertheless, the temperature problem is still the same. I read a lot how important a good baffling is.

Today, I took some pictures with my smartphone from the oil filler door. Especially IMG_1904 shows that the baffle is folded back. ( on the pilot's side/ that's where the oil cooler is).

Then, we took the opportunity to remove and re-assemble the upper cowling with 2 person. To be honest - we were not able to replace the cowling with the baffle folded forwarded on the whole left side.

But, I was able to correct the baffle by hand from the oil-filler-door. It was surprisingly easy to pull the back-folded part to front.

The next picture show the result: IMG_1927 and _1934 proove that the baffle is now folded forward.

I did not had the oppoprtunity to do a test-flight, but I have some questions:

1. It was so easy to correct the baffle manually, that I fear, the baffle can flip backward again from the power of the air-stream. Hmmm, Let's see what happens after a  test-flight.

2. In case it does flip back - what can I do?

3. IMG_1934 shows a lot of "folds" or at least waves  of the baffle. Is that sufficient?

4. IMG_1905 is a picture more to the center part of the baffle. Is that fold a problem? Obviously, somebody tried to improve with cable ties. Should this fold be improved?

5. I have no idea how to inspect or in case correct the baffling on the right side. There is no oil filler door. Of course, I can try the famous "shop-light-test"

[Hank]

The thing to remember about averages, regardless of what is being averaged, is that fully 50% of the samples will be above average; the other 50% will be below average. 

On the other hand, Photos #3 & 4 look like the baffling was not cut to size correctly, or else put together wrong. But I'm not an A&P, so whadda I know?

[jetdriven]

that sounds like the median. Half of planes more, half less. Average is  the average is all CHT values / number of aircraft. 

You can rivet a couple  .025 x 1/2" x 4" strip sof aluminum to the baffle seal on the inside. this prevents the seal from rolling and tucking under. We had to do this and its been fine for 6 years now.

Edited September 23, 2018 by jetdriven

[Hank]

3 hours ago, jetdriven said:

that sounds like the median. Half of planes more, half less. Average is  the average is all CHT values / number of aircraft. 

You can rivet a couple  .025 x 1/2" x 4" strip sof aluminum to the baffle seal on the inside. this prevents the seal from rolling and tucking under. We had to do this and its been fine for 6 years now.

When samples are reported in whole numbers, yiu are likely to have several repprted with the median value (same numbers of values abive as below), but are unlikely to have any report with the average value, such as 386.73°. But out of 100 samples, there may be several reported at the median value of 382, with 42 higher, 42 lower and 8 right at 382°.

Also remember:  there are lies, damned lies and statistics.  

[Guest]

I would get a leather hole punch and put an 1/8” hole at each of the puckers, then using a sharp knife cut from the hole to the edge of the baffle tape.  This will allow the puckers to flatten out and seal against the cowls.  

Clarence

[INA201]

Let’s face it, that baffling needs some tightening up.

[Jim F]

Hi NicoN,

There are two problems with the TSIO-360-GB/LB, high CHT and driver inputs.  Both can be controlled to make the 231 a outstanding value.  

CHT, that baffle seal should be corrected or replaced. GeeBee sells a kit with pre cut seals. The way I look at this is SEE THE AIR.  Any leak is bad for a already warm running engine. Remember that poor baffling will cause CHT to increase and that will cause higher oil temp.  Also the poor baffling means less cooling air pushing through the oil cooler. 

Pilot inputs, just treat her gental and keep the engine in your scan. 

Good luck,

Jim

[carusoam]

To find @GEE-BEE...

-a-

[Shadrach]

On 9/23/2018 at 2:53 PM, NicoN said:

Good evening!

We have a 1980 M20K and are experiencing quite high oil temperature and high CHT #4.

Oil temperature is most of the time between 205 and 215 - which is still in green arc but Savvy says, it's higher than the majority of the fleet.

Also #4 tends to go as high as 410. All other cyls have normally CHTs below 380.

On our last 50h maintenance, the mechanic and I removed the upper cowling and suspected that the baffling on the pilot's side was at least partially folded back.

A did not assist him re-assembling the cowling, so I am not sure that the baffling was correctly folded forward at that point.

 

Nevertheless, the temperature problem is still the same. I read a lot how important a good baffling is.

Today, I took some pictures with my smartphone from the oil filler door. Especially IMG_1904 shows that the baffle is folded back. ( on the pilot's side/ that's where the oil cooler is).

Then, we took the opportunity to remove and re-assemble the upper cowling with 2 person. To be honest - we were not able to replace the cowling with the baffle folded forwarded on the whole left side.

But, I was able to correct the baffle by hand from the oil-filler-door. It was surprisingly easy to pull the back-folded part to front.

The next picture show the result: IMG_1927 and _1934 proove that the baffle is now folded forward.

I did not had the oppoprtunity to do a test-flight, but I have some questions:

1. It was so easy to correct the baffle manually, that I fear, the baffle can flip backward again from the power of the air-stream. Hmmm, Let's see what happens after a  test-flight.

2. In case it does flip back - what can I do?

3. IMG_1934 shows a lot of "folds" or at least waves  of the baffle. Is that sufficient?

4. IMG_1905 is a picture more to the center part of the baffle. Is that fold a problem? Obviously, somebody tried to improve with cable ties. Should this fold be improved?

5. I have no idea how to inspect or in case correct the baffling on the right side. There is no oil filler door. Of course, I can try the famous "shop-light-test"

The pic above is low hanging fruit.  That baffle seal should be faced forward.  A mechanic should know better than to install a cowling with the baffle seal mashed and facing in the wrong direction.

[NicoN]

Thank you for all postings.

To give you a short update:

I did a 1 hour test-flight These days:

Cyl #4 never reached 380°F not in climb not in cruise with 65% LOP. It is still about 30° hotter than others but definitely within the 380-limit. All other cyls are also cooler than before.

Oil temperature is lower than before about 195°, but no more 215°F !

I also did a fast descent with airspeeds of 185kts @ 3000ft and cowl flaps closed to test the baffles

 

And the miracle: after landing the baffles are still folded Forward.

I guess, I still lose some cooling air caused by the folds fo the baffles, but it is definitely a large step Forward.

 

[81X]

How are the EGT's on #4?  If high, it could be a valve or injector issue, but that baffling did look pretty sad.  My 231 baffling is like m20doc says- it has a punch and cut so the folds lay flat- cylinders run less than 380 always except for the steepest of climbs on a hot day.  

[NicoN]

I am studying your hints and picture and do not understand all of it (may be it's my english )

"Rear baffle seal must be pulled tight during install so you have a 30/40 degree forward bend ".

I think, you want to have the baffle folded forward for itself even with the cowling removed. I can see on the left side at the corner that the baffle is cut and  a small piece inserted.

Indeed, with the cowling removed my baffle does not look that bad and quite similar to your pictures.

As I described, the rear baffle tends to fold back with the cowling re-assembled. I can reach at least the left hand side from the oil filler cutout and pull the baffle forward.

Do you have then also remaining folds ?

4 hours ago, GEE-BEE said:

pull seals tight when install 

What dows that mean?

 

4 hours ago, GEE-BEE said:

sides down ward

Really? Ours are bent upward, which sounds logic to me as the high pressure from the incoming air seals the baffle onto the cowl and the air is forced to flow down between the cylinders

downward sounds to suited to seal

[Guest]

1 hour ago, NicoN said:

I am studying your hints and picture and do not understand all of it (may be it's my english )

"Rear baffle seal must be pulled tight during install so you have a 30/40 degree forward bend ".

I think, you want to have the baffle folded forward for itself even with the cowling removed. I can see on the left side at the corner that the baffle is cut and  a small piece inserted.

Indeed, with the cowling removed my baffle does not look that bad and quite similar to your pictures.

As I described, the rear baffle tends to fold back with the cowling re-assembled. I can reach at least the left hand side from the oil filler cutout and pull the baffle forward.

Do you have then also remaining folds ?

What dows that mean?

 

Really? Ours are bent upward, which sounds logic to me as the high pressure from the incoming air seals the baffle onto the cowl and the air is forced to flow down between the cylinders

downward sounds to suited to seal

When installing the aft baffle seal, keeping it under tension by pulling on the material as you rivet it to the metal baffle will impart a natural bend forward.

I also install rivets at about a 1” or 30mm spacing to avoid puckers between the rivets.

Clarence

 

[DanM20C]

On 10/6/2018 at 7:07 PM, 81X said:

How are the EGT's on #4?  If high, it could be a valve or injector issue, but that baffling did look pretty sad.  My 231 baffling is like m20doc says- it has a punch and cut so the folds lay flat- cylinders run less than 380 always except for the steepest of climbs on a hot day.  

I was thinking the same thing.  If #4 is cooler (EGT) than the rest when ROP and hotter when LOP, or vise versa, It's probably related to that injector flow.  If #4 is hotter all the time (LOP and ROP) it could be a valve. 

Also check the area between #2 and the oil cooler.  Especially near the case, this is the area that the oil filler, dipstick, and oil temp probe are located. This area should be sealed off well.  I have seem some poor to no baffling in this area.  

Cheers,

Dan

[NicoN]

Okay. I will keep an eye on it.