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M20U Ovation Ultra Cylinder #5


k8n

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Thanks for posting that.  Mine is about 3/4” to 1” narrower than that.  Given my temp on #5 has been much closer to the others with the hole cut the way I have it now, we could probably do better with that pattern.  I’ll run it by my IA during annual in May and see if he agrees.  I like the fit/layout of those baffles too.

Steve

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Am I missing something? How does that picture differ from this one, a pre-pixied baffle?  BTW, I did finally recruit my hangar elf to help with the cause and am seeing a good 20-30 degree reduction in #5 CHTs. 

 

baffle mod pics 001.jpg

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You are not missing anything. One version of the pixie hole is seen in this photo. There is no pixie hole on the new Ovation. The Ovation Ultra in the first photo is scheduled for delivery next week.

pixie_hole_.jpg

Edited by k8n
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Yup! I lived with it for three years and finally applied the fix. There are a few threads here that cover this. Just do a search on “pixie hole”. I have some photos that another MSer gave to me to show you exactly where to put it. PM me if you want them.

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Is it necessary to remove the baffle before drilling the hole?  I am by no means suggesting I will go boring in there with my dewalt rotary hammer willy nilly, but if it could be drilled in situ that would be advantageous.  Guess not sure how the baffling is attached, some of the baffling looks like it is only to be removed once every blue moon, but it is an aviation installation.  I guess I should stop keyboard warrioring and go look....but the airplane is at a different avionics shop.

 

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Is it necessary to remove the baffle before drilling the hole?  I am by no means suggesting I will go boring in there with my dewalt rotary hammer willy nilly, but if it could be drilled in situ that would be advantageous.  Guess not sure how the baffling is attached, some of the baffling looks like it is only to be removed once every blue moon, but it is an aviation installation.  I guess I should stop keyboard warrioring and go look....but the airplane is at a different avionics shop.
 

Can be done by the night elves insitu. I’ve “heard” the Elves used a 1” Diamond hole cutter. Put a piece of sheet steel behind the aluminum baffle. Between the baffle and the cylinder to protect the cylinder. The rest of the area was covered with tape sticky side up to protect the adjacent parts and collect shavings. Very slow careful drilling/cutting.


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That method has worked. However, we discovered that it’s very easy to remove the two screws at the left edge of that front baffle and pull it away enough to safely use a drill bit.  3/4” is what we used, per the recommendations from another elf.

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9 hours ago, N231BN said:

You do realize that hole just cools the probe, not the whole cylinder?

This has always been my understanding, too, that the hole provides localized cooling for the area around the probe but does very little for the overall cylinder cooling.

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19 minutes ago, jetdriven said:

why doesnt anyone cut the baffle down more like where this red line is. It works on the M20J.

5a961f0dab636_bafflemodpics001.jpg.c96a0026e147b4e846629513274bb389.jpg

I wonder if the same strategy would work for the obnoxiously hot #2 on my C.  IT's consistently 30 degrees hotter than the rest and makes me waste ~1gph to limit CHT to the 380s in cruise in the summer.

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41 minutes ago, jetdriven said:

why doesnt anyone cut the baffle down more like where this red line is. It works on the M20J.

5a961f0dab636_bafflemodpics001.jpg.c96a0026e147b4e846629513274bb389.jpg

Because on the Continental your red line cuts through the alternator connections, Byron! :P

  • Haha 1
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44 minutes ago, Andy95W said:

This has always been my understanding, too, that the hole provides localized cooling for the area around the probe but does very little for the overall cylinder cooling.

The probe sticks in a good 1.5 inches and only reads the temp at the tip of the prob. My thoughts are it’s pretty consistent.  All the cylinders get downdraft cooling but #5 has the alternator blocking some flow/pressure along with some alternator cooling holes cut into the baffling in that area that might lower the pressure differential.  The holes that I’ve seen are larger and rectangular but the drilled out ones are probably easier to make. 

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  • 2 years later...
On 3/1/2018 at 12:29 PM, MIm20c said:

The probe sticks in a good 1.5 inches and only reads the temp at the tip of the prob. My thoughts are it’s pretty consistent.  All the cylinders get downdraft cooling but #5 has the alternator blocking some flow/pressure along with some alternator cooling holes cut into the baffling in that area that might lower the pressure differential.  The holes that I’ve seen are larger and rectangular but the drilled out ones are probably easier to make. 

Hi here 
Let me know if it works well? Do you have any suggestion?

Ezequiel

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Welcome aboard, Ezequiel.


The pixie hole seems to have changed over the years...

The need...

Airflow into the cowling in front of cyl #5 is obstructed by the alternator...

The cowling has a piece in the nostril that blocks air flow...

So the fiberglass piece gets a US 25cent piece hole cut in it by hangar fairies...aka pixies... generally not real mechanics for legal reasons in the US...

Cooling airflow for the IO550 is generally supposed to be from the top of the cowl to the bottom... the front two cylinders also have the airflow coming into the cowling

keep in mind...
Adjusting baffling that can alter the air flow direction... may be counter productive...

If the baffle gets adjusted too much or in the wrong place... pressure in the lower half of the cowl can start to rise... the effect will be improved cylinder cooling for one, but less cylinder cooling overall...

Take good before and after CHT data for comparison...

 

With the top cowl off... look down the cylinders to see the path that the cooling air takes...

Air pressure at the top of the cowl should be higher than the lower part of the cowl...

 

My O has a whole in the cowl material allowing improved airflow to the first cylinder... #5.  It got there prior to my ownership 10years ago... #5 still has a warmer CHT...

With every digital engine monitor... be sure to know how many CHT sensors you have... which one is considered the ship’s CHT sensor... is one CHT sensors compromised by being different than the others... via a piggy back arrangement or gasket thermocouple... location on the cylinder can make a big difference... 25°F...

Some very good data provided by very knowledgable Mooney owners provided in this thread...

PP thoughts only, not a mechanic...

Best regards,

-a-

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Thank you for your time.
 when you say:
"the fiberglass piece gets a US 25cent piece hole cut in it by hangar fairies...aka pixies" and when you say " My O has a whole in the cowl material allowing improved airflow to the first cylinder... #5. " Are you talking about the same thing or not? 
Do you have any pictures?
Now a days in the factory  Do you know what they are doing to solve this inssue?

Thank you for your understanding.
Ezequiel
 

20191226_103827.jpg

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Ezeq,

I wrote about the same thing in two different ways... trying to improve what I was describing...

As in the fiberglass on my plane got modified, not the aluminum...

You can see that other people went to the next level and altered the aluminum as well...

My plane, went in a different direction... it got new sheet metal to match with different cylinders.. they came with the IO550(N), in place of what is on the (G)...

(N) cylinders have probably gone out of favor with a more common crack forming in their heads...

 

So... the number 5 cylinder does have a Tendency to get hot...  But yours is really standing out as in hotter than the rest...

There may be some airflow leaking, or not being controlled as well as it should be... Rubber gasket seals and other sheet metal pieces controlling air flow.,.

There may be some data that you can access on Savvy.com

Savvy allows you to compare EGTs and CHTs to other Mooneys with the same engine...  see if you #5 is closer to other #5s...

Private Pilot thoughts only, not a mechanic...

Best regards,

-a-

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