Interesting engine baffle observation...

[Shadrach]

I know someone who recently hung a Lyc IO360A1A on his vintage Mooney. After reading a bit here and there on the internets, he learned that he might improve airflow over his #3 cylinder by wedging a small piece of baffle seal material between the baffle wall and the innermost cylinder wall. Test flights have shown impressive results. #3 is still the hottest in climb, but only by a small margin, and #2 is now the hottest in cruise.  He is very pleased with the outcome and thought it may be of value to others... 

[KSMooniac]

Very nice trick!  To be anal-retentive, that looks like a piece of baffle SEAL material, and not baffle material.    

In a somewhat related story on my J with a completely different cowl/baffle arrangement, I had Maxwell fix a crack in the front piece of my baffle near cylinder #2, and that really helped even out my airflow underneath the cylinders resulting in a much smaller CHT variation, even with the #1/#3 jugs on the other side!  

[Shadrach]

Duly noted and edited....

[PTK]

I'm not sure I'd want to fly around with something wedged in my engine compartment that may very well come loose.  Is this thing wedged literally or am I missing something?

[jetdriven]

Ours, #1 is the hottest cylinder at all times

 

[Shadrach]

Quote: allsmiles

I'm not sure I'd want to fly around with something wedged in my engine compartment that may very well come loose.  Is this thing wedged literally or am I missing something?

[Shadrach]

Quote: jetdriven

Ours, #1 is the hottest cylinder at all times

 

[Cruiser]

Quote: jetdriven

Ours, #1 is the hottest cylinder at all times

 

[jetdriven]

nope, it peaks at the same fuel flow as all the others.  it just runs 20-30 degrees hotter at all times.

[danb35]

On mine, #2 is the hottest.  Cyl. #1 is significantly cooler (~100 deg F cooler), but I suspect an instrument issue with that, as the EI CHT probe is piggy-backed on the factory probe on #1.

[jetdriven]

Our #3 is like that, it is a 3/8" washer thermocouple under the factory bayonet probe.  Works great.

[Jeff_S]

I just learned something about my engine that helps explain some readings on the JPI. With the cowling off for an oil change, I noticed a single sensor wire attached to the top spark plug on #3, with nothing on the others. My A/P said that's because the factory CHT sensor uses the bottom plug, so the original installers put the #3 JPI sensor on the top while putting all the other JPI sensors on the bottom. And I have always noticed that #3 CHT gets the hottest in climb on the JPI. Once in cruise they level out nicely.

It all makes sense to me. Heat rises, and airflow in climb isn't as strong as in cruise, plus power is higher of course. Just one more little mystery solved.

[Shadrach]

Quote: Jeff_S

I just learned something about my engine that helps explain some readings on the JPI. With the cowling off for an oil change, I noticed a single sensor wire attached to the top spark plug on #3, with nothing on the others. My A/P said that's because the factory CHT sensor uses the bottom plug, so the original installers put the #3 JPI sensor on the top while putting all the other JPI sensors on the bottom. And I have always noticed that #3 CHT gets the hottest in climb on the JPI. Once in cruise they level out nicely.

It all makes sense to me. Heat rises, and airflow in climb isn't as strong as in cruise, plus power is higher of course. Just one more little mystery solved.

[takair]

What is the theory behind this?  Looking at the pictures, it looks like the area at the engine mount is not well sealed.  I wonder if this wedge has simply closed off more of that opening and provided a tighter seal and thus redirected the airflow where it should have gone in the first place.  In other words, would sealing the baffle to engine with RTV have done the same thing.  Hard to tell without seeing the entire thing.  Sorry to be a skeptic, I just don't understand the theory behind this. 

[Shadrach]

Take some time to familiarize yourself with the cylinder head design of the Lyc angle valve 360 (I'm not sure about the parallel valve engines). See the 1st attached photo...I'm shining a shop light in the lower cowl compartment. Looking down from the top through the  cylinder head fins of cylinders #1 and #3, it's appearant that there is no light visible on the back side of cylinder #3 (the rear cylinder)... This is because the fins do not encircle the cylinder barrel completely. This is obvious when looking at the rear side of cylinder one (2nd attached photo). However, there is airflow around cyl #1 because it buts up against the front side of cyl#3. The back side of cyl #3 is butted up against the baffle wall.

Mooney tried to solve this by by putting a pocket in the back side of the passenger side baffle wall (see 3rd attached pic) Cessna did not, and I understand that Cardinals suffer from a higher temps on cyl#3 for that reason. It is rumored that George Braly (of GAMI fame) came up with the "baffle seal wedge fix" to help the Cardinal baffle circulate air around cyl #3. I did it because "the pocket" did not seem to be letting enough airflow through as #3 was always significantly hotter. The "wedge" holds the the baffle wall off the cylinder allowing for additional airflow. I did a number of baffle tweaks during the engine install so the effects are probably cumulative. None the less, cyl #3 now runs about 50df cooler than before.

Edited July 19, 2021 by Shadrach

[takair]

Thanks for the explanation, makes more sense now.  Will have to look closer at my E model next time I have the cowl off.  My CHT are fairly even, #2 is hottest.  Hottest EGT is number 3.  I suspect this would only help CHT.

[Shadrach]

Quote: takair

Thanks for the explanation, makes more sense now.  Will have to look closer at my E model next time I have the cowl off.  My CHT are fairly even, #2 is hottest.  Hottest EGT is number 3.  I suspect this would only help CHT.

[PTK]

Quote: Shadrach

I should have mentioned that it's RTV'd (high temp) in place... If it were to actually come loose, what kind of mayhem do you think a 2X10MM piece of silicone rubber would cause?

[KSMooniac]

Baffles are primarily done by the airframer, not Lycoming.  It is quite possible (probable, in fact) that Mooney did not find the optimum baffle design/solution when developing the various airframes...just look at the differences between a pre-J and a J, or even an Acclaim and an Acclaim Type S and you'll see that there are always improvements to be had.  Also check out the GAMI/Tornado Alley baffles for Bonanzas vs. the Beech version for another example.

[Shadrach]

Quote: allsmiles

If needed to be there Lycoming would have put it there! I don't want anything wedged or loose in my engine compartment.  I'm a little weird this way!

[PTK]

Quote: Shadrach

Yes, you've made it oh so clear that you believe that little to no innovation occurs outside of the factory...even when you're unsure of which factory is responsible for the engineering.   I made it very clear that the baffling was a Mooney part when I made the comparison to the Lyc IO360 in the C177 Cardinal.  Perhaps you would have believed me if I had "factory" credentials...  Thankfully no one is holding a gun to your back and making you do all these weird things to your plane.  I wish you the very best in your very devout following of the book... It seems in your world every piece of machinery was engineered to the max at the factory and that everything that needed to be learned was learned and applied at production time by factory workers that always performed consistently.

I am unfortunately stuck in my world, which is slightly different than yours.

[Shadrach]

Quote: allsmiles

Oh yes my friend Ross! I hope you don't mind I'm calling you a friend!  I thought you would bite after my last posting! (1) I don't mind you disagreeing but if you would please interpert my postings correctly.  I never ever ever said that little or no innovation occurs outside the factory.  As I never ever said  that every piece of machinery was engineered to the max by the factory.  I have no reason not to believe you, factory credentials or not.  What I did say in no uncertain terms is that the factory engineers the engines so well and with built in margins precisely because they don't engineer it to the max if you know what I mean.  Margins like these have saved many ignorant pilots out there from destroying their engines.  I include myself in that group of ignorant pilots.  I read a lot on these things and I am constantly learning.(2) Personally I don't know everything there is to know and I am a firm believer in that some things are best left to the professionals with the know how.  Engine management is one of those things that I leave to and learn from professional engineers who designed it tested it and have the data behind it.(3) Incidentally these are the same people who put their money where their mouth is and take the responsibility by signing on the dotted line.  I will adhere to Lycoming recommendations.  Whose recommendations do you adhere to?(4) 

[jetdriven]

FWIW I tried this on my engine and it helped, perhaps 20 degrees.

[fantom]

Quote: allsmiles

...I include myself in that group of ignorant pilots...

[Shadrach]

Quote: jetdriven

FWIW I tried this on my engine and it helped, perhaps 20 degrees.