1346w

Under cylinder baffles

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New member, but I've been reading and observing for two years since I bought my first Mooney. Like most c model owners, I fight with cylinder temps. I've done my absolute best at sealing the plenum and all baffles around the front of the cowl. I'm positive it can't get any better... Still seeing high temps on climb out and takes a long time to come down even when I level off. A little background on my airplane, 1964 m20c, low time engine, powerflow exhaust, lasar cowl closure and factory single cylinder temp gauge in the #3 cylinder.

My question is, should I consider altering/adjusting the metal baffles that wrap around underneath the cylinders? Do they need to slow down the airflow or can the air be sped up by removing some of the airflow restriction?

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45 minutes ago, 1346w said:

New member, but I've been reading and observing for two years since I bought my first Mooney. Like most c model owners, I fight with cylinder temps. I've done my absolute best at sealing the plenum and all baffles around the front of the cowl. I'm positive it can't get any better... Still seeing high temps on climb out and takes a long time to come down even when I level off. A little background on my airplane, 1964 m20c, low time engine, powerflow exhaust, lasar cowl closure and factory single cylinder temp gauge in the #3 cylinder.

My question is, should I consider altering/adjusting the metal baffles that wrap around underneath the cylinders? Do they need to slow down the airflow or can the air be sped up by removing some of the airflow restriction?

There’s a specific measurement that should be set for the gaps at the bottom of the cylinders between the center cylinder baffle and the front and rear wrap around baffles. I don’t have them off the top of my head right now, but will work to locate them. Carbureted engines run warmer than injected engines. Just the nature of the beast. I recommend getting a four cylinder CHT/EGT gauge and don’t rely on the accuracy of the original single cylinder gauge. 
David

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54 minutes ago, 1346w said:

New member, but I've been reading and observing for two years since I bought my first Mooney. Like most c model owners, I fight with cylinder temps. I've done my absolute best at sealing the plenum and all baffles around the front of the cowl. I'm positive it can't get any better... Still seeing high temps on climb out and takes a long time to come down even when I level off. A little background on my airplane, 1964 m20c, low time engine, powerflow exhaust, lasar cowl closure and factory single cylinder temp gauge in the #3 cylinder.

My question is, should I consider altering/adjusting the metal baffles that wrap around underneath the cylinders? Do they need to slow down the airflow or can the air be sped up by removing some of the airflow restriction?

What David says is your best bet, however, do you know your takeoff, sea level fuel flow?

 I second getting some type of egt cht for all the cylinders.  It may be worse or better than you think... or you might find just one warm cylinder and then start looking at intake leaks, ignition issues, etc.

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39 minutes ago, Sabremech said:

There’s a specific measurement that should be set for the gaps at the bottom of the cylinders between the center cylinder baffle and the front and rear wrap around baffles. I don’t have them off the top of my head right now, but will work to locate them. Carbureted engines run warmer than injected engines. Just the nature of the beast. I recommend getting a four cylinder CHT/EGT gauge and don’t rely on the accuracy of the original single cylinder gauge. 
David

So more than likely, what's under my cylinders is what lycoming/Mooney wants as far as sizing, but the gaps might need adjusting.

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16 minutes ago, 1346w said:

So more than likely, what's under my cylinders is what lycoming/Mooney wants as far as sizing, but the gaps might need adjusting.

Correct. They may need adjusting to ensure they are the same. The measurement is different for the opening closest to the crankcase halves than the opening towards the cylinder head. The important thing is to have them as close to the same on all four cylinders. Again, I’lol locate the measurement unless someone beats me to it. 

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21 minutes ago, 1346w said:

So more than likely, what's under my cylinders is what lycoming/Mooney wants as far as sizing, but the gaps might need adjusting.

I’m not sure of the dimension David is referring to, but the opening formed by the Lycoming inter cylinder baffles and the Mooney baffles will affect the flow around the cylinders.  Ideally multi probe engine monitors are the best solution.

You can alter the width of the baffle to improve the cooling, also the fit of the forward rubber l seal has a great effect.

Clarence

0E20E409-5FC3-49E5-8C75-9B705F0CF505.jpeg

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22 minutes ago, Sabremech said:

Correct. They may need adjusting to ensure they are the same. The measurement is different for the opening closest to the crankcase halves than the opening towards the cylinder head. The important thing is to have them as close to the same on all four cylinders. Again, I’lol locate the measurement unless someone beats me to it. 

Awesome! I appreciate your help. 

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14 minutes ago, M20Doc said:

I’m not sure of the dimension David is referring to, but the opening formed by the Lycoming inter cylinder baffles and the Mooney baffles will affect the flow around the cylinders.  Ideally multi probe engine monitors are the best solution.

You can alter the width of the baffle to improve the cooling, also the fit of the forward rubber l seal has a great effect.

Clarence

0E20E409-5FC3-49E5-8C75-9B705F0CF505.jpeg

The forward rubber seal, if we speak of the same seal, is new and fits about as well as one could get it. I even took silicone and ran around the bottom where the rubber sits in the little tray at the front of the cowl. I'll probably regret that move when I need to remove the bottom front cowl piece for anything, but I was desperate....

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1 hour ago, Ragsf15e said:

What David says is your best bet, however, do you know your takeoff, sea level fuel flow?

 I second getting some type of egt cht for all the cylinders.  It may be worse or better than you think... or you might find just one warm cylinder and then start looking at intake leaks, ignition issues, etc.

I've got no way of measuring fuel flow, just fuel pressure. 

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37 minutes ago, 1346w said:

I've got no way of measuring fuel flow, just fuel pressure. 

One relatively inexpensive engine monitor that will give you what you need is the Insight Avionics G2.

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I’m curious whether anyone has ever attempted a mod for the guppy mouth that changed the contour/opening at the top/ sides of the cowl inlet... and whether someone has taken the existing cowl enclosure mod one step further by extending the bottom of the inlet all the way to the front cylinder baffling in an effort to reduce back flow/turbulence in that area?

Edited by PilotCoyote

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4 hours ago, 1346w said:

New member, but I've been reading and observing for two years since I bought my first Mooney. Like most c model owners, I fight with cylinder temps. I've done my absolute best at sealing the plenum and all baffles around the front of the cowl. I'm positive it can't get any better... Still seeing high temps on climb out and takes a long time to come down even when I level off. A little background on my airplane, 1964 m20c, low time engine, powerflow exhaust, lasar cowl closure and factory single cylinder temp gauge in the #3 cylinder.

My question is, should I consider altering/adjusting the metal baffles that wrap around underneath the cylinders? Do they need to slow down the airflow or can the air be sped up by removing some of the airflow restriction?

What kind of temperatures are we talking?  Are you breaking 400?

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41 minutes ago, PilotCoyote said:

and whether someone has taken the existing cowl enclosure mod one step further by extending the bottom of the inlet all the way to the front cylinder baffling in an effort to reduce back flow/turbulence in that area?

The ARI cowl mod (upon which Sabremech based his initial forays into making a new cowl, if I am not mistaken) has a piece of aluminium that smooths the passageway from the edge of the new cowling to the pressure plenum.  I've considered attempting something similar.  I have the LASAR guppy mouth closure.  I'm not sure I could get that accomplished under a "minor modification"...  I also know that some mooneys take air from in that dropped down area (of turbulance) to feed the cuff around the muffler...  Covering that drop down too tightly might be counter-productive for them.

I have to say, I like the direction of this topic.  I would be very interested in those distances for the baffles as Sabremech has mentioned.  My C model runs hot.

I am also waiting with some excitement for Sabremech's replacement cowl.  It will include new baffling (mine is original and patched beyond recognition).  I don't know if I can scratch together the AMUs to get one, but I hope so.

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1 hour ago, takair said:

What kind of temperatures are we talking?  Are you breaking 400?

I broke 400 today in Colorado with a oat of 9°f.

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2 hours ago, PilotCoyote said:

I’m curious whether anyone has ever attempted a mod for the guppy mouth that changed the contour/opening at the top/ sides of the cowl inlet... and whether someone has taken the existing cowl enclosure mod one step further by extending the bottom of the inlet all the way to the front cylinder baffling in an effort to reduce back flow/turbulence in that area?

I've considered the same thing. Seems odd to put the cowl closure on, but leave the place open between it and the cylinders. A simple piece of sheet metal and rubber baffle material would possibly stop turbulent airflow into the plenum.

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1,

you have a discussion about hardware changes going on with some pretty sharp hardware guys...

If I bought their solution, I would still need the instruments to tell me that my set-up is matching all the others on the planet...

I would immediately find that there is a procedure to keep the CHTs under control...

how do you feel about the climb procedure you are using?  What guidelines are you using?

how do you feel about the single CHT instrument you have? Or the single uncalibrated EGt that is available...

What is your plan for monitoring your updates?

Summary...

1) For long term success...

2) Proper hardware... includes proper sealing of the existing dog house, as you have done...

3) Proper instruments... you have four independent single cylinder engines that deserve their own instrumentation...

4) Proper procedures... Climb angles/speeds mixture setting

5) Side benefit for the M20C is carb temp... FF is an extra benefit...

6) When you have that in place and still want better control... there is that recent cowl update...

7) you broke 400°F on your single ancient instrument?  When others prefer 380°F with fully modern cowls and fully modern instruments...

8) are you sure something is wrong?

9) Certainly the solution isn’t to fix one thing...

10) Expect the solution to be three-fold...

  • Procedure
  • Instruments
  • hardware

Yes I had an M20C for a decade, with a single CHT sensor... no FF, no carb temp...

Is there a limit to the budget on this project?

PP thoughts only, with only so much vision... I went with the cowl mod, instruments, and procedure... and added fuel injection... with curvy balanced intake pipes... :) CHTs in the range of 320-380°F are possible...

Best regards,

-a-

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12 hours ago, 1346w said:

I broke 400 today in Colorado with a oat of 9°f.

What airspeed do you climb at?

Im sure the issue has a component of design/condition of your baffles, but there are lots of operational things you can control to make the problem worse or better... are your cowl flaps working properly and set properly?  What airspeed do you climb at?  Most people cruise climb at around 120mph which will increase airflow and cooling noticeably over Vy or Vx.  Fuel flow is very important too.  A small reduction in whats required can have an outsized heat penalty at full power and low speed.  

So Denver... I had my worst cylinder heat issue there too, but it was in the summer... be very careful leaning for takeoff.  If you need to, do it, but make sure you’re clearly rich of max power.  The thin air at higher altitude (Denver) doesn’t cool as well, so a speed increase in climb will help increase volume of cool air.

By all means, keep looking at the mechanics of cooling your engine, but be open to operating in a “cooler” way.  

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4 hours ago, Ragsf15e said:

What airspeed do you climb at?

Im sure the issue has a component of design/condition of your baffles, but there are lots of operational things you can control to make the problem worse or better... are your cowl flaps working properly and set properly?  What airspeed do you climb at?  Most people cruise climb at around 120mph which will increase airflow and cooling noticeably over Vy or Vx.  Fuel flow is very important too.  A small reduction in whats required can have an outsized heat penalty at full power and low speed.  

So Denver... I had my worst cylinder heat issue there too, but it was in the summer... be very careful leaning for takeoff.  If you need to, do it, but make sure you’re clearly rich of max power.  The thin air at higher altitude (Denver) doesn’t cool as well, so a speed increase in climb will help increase volume of cool air.

By all means, keep looking at the mechanics of cooling your engine, but be open to operating in a “cooler” 

Should I try full rich takeoffs? I usually lean for takeoff in the summer, but not as aggressive in the winter. Usual climb outs are between 100-120 mph. I'm going to start with better cht monitoring go from there.

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26 minutes ago, 1346w said:

Should I try full rich takeoffs? I usually lean for takeoff in the summer, but not as aggressive in the winter. Usual climb outs are between 100-120 mph. I'm going to start with better cht monitoring go from there.

For Density altitude above ~5,000, yes, you should lean somewhere rich of max power.  It will not be very much different than full rich.  At density altitude below ~5000’, full rich is appropriate.

There are better ways to lean (like Target egt) during climb, but you need an engine monitor with all 4 cylinders.  Even with a good engine monitor, i start takeoffs below 5k with full rich.

After takeoff, use Vy to a safe altitude (~100mph to pattern altitude or whatever you consider safe), then pitch down slightly to get 120mph and continue your climb at 120 until cruise altitude.  Rpm should stay at 2600-2700.  If you’re still getting above 400 cht you can richen slightly.  

I think being slightly richer and faster is going to make a big difference for you.  We have a paper around here somewhere that shows climbing at a speed higher than Vy is more efficient on cross country flights, so your climb rate may decrease slightly but you make up for it with more distance downrange.  You will probably only notice a very small decrease in climb.  And it’ll definitely help your cylinder temps.

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18 hours ago, 1346w said:

I broke 400 today in Colorado with a oat of 9°f.

What climb airspeed are you using and at what altitude?  I'm breaking in a new engine which should be hot, but at 120-125mph climb even on 60F day, 374 is the highest CHT I'm seeing.  302 to 324 in 77% power cruise.  What is your fuel flow in climb?  If it helps I'm in the 15 to 16 gph range full rich.  Are you sure your cowl flaps stay open in the climb?  I know someone that had that issue, their cable was about to break.  On the ground it didn't take much hand pressure on the flap to close it.  He mounted a GoPro cam near the flap and sure enough around 100 mph the flaps closed even though he had the rod pulled out.  If memory serves, there was a spring on the system connected backwards too.  Just some thoughts, I'm not an A&P nor do I play one on TV :-)  I am also new to the M20 ownership, more like a love affair so far.  Hopefully it doesn't break my heart.

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1,

You seem to be discussing issues that are often covered in transition training...

Not trying to be difficult, but your questions can’t be answered properly, when you leave out so much critical detail...

If it is lack of familiarity with your machine... please seek some additional ops training...

Seek out a Mooney specific CFII... get as much as out of the hours as possible...
 

Continue to ask questions... and searching for details... :)

Best regards,

-a-

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15 hours ago, 1346w said:

Should I try full rich takeoffs? I usually lean for takeoff in the summer, but not as aggressive in the winter. Usual climb outs are between 100-120 mph. I'm going to start with better cht monitoring go from there.

I would suspect if you did 120 on the climb your temperature issue would go away and your rate of climb would be very close to the same.  

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