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High CHT and one High EGT


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9 minutes ago, Hector said:

Guppy mouth C’s May have more trouble keeping temps in check.
 

 

FWIW I have the LASAR cowl enclosure.  I've as yet to hear anyone report that installing one helped anything other than aesthetics.  I can personally attest that it makes sealing large gaps in the baffle on the prop side of the starter and alternator impossible without dropping the bottom cowl.  

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On 3/8/2019 at 8:50 AM, Hank said:

Good Lord! 14 gph in a C! Mine runs 9 . . . But I also don't fly at 25"/2500. If you ignore units and just look at the numbers on the MP and Tach dials [that you used to have], these would be 25 / 25. Using the Key Number approach, this gives 25 + 25 = 50, which puts you at pretty high power. For the O-360 engine in our Cs, we should fly at Key Number of 47 or less.

Where do you see 14 gph?  The scanner display is showing 14.2 gallons used (USD), but I can't make out the actual gph.  @Pilotja5, do you have any bigger pictures of the display or data logs?

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2 hours ago, DXB said:

FWIW I have the LASAR cowl enclosure.  I've as yet to hear anyone report that installing one helped anything other than aesthetics.  I can personally attest that it makes sealing large gaps in the baffle on the prop side of the starter and alternator impossible without dropping the bottom cowl.  

The guppymouth actually has reverse airflow, coming OUT the front of the cowl. Closing off the bottom improves air flow, cooling and speed.

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18 minutes ago, Hank said:

The guppymouth actually has reverse airflow, coming OUT the front of the cowl. Closing off the bottom improves air flow, cooling and speed.

I get that's the idea, but I've as yet to hear anyone who has installed one indicate that it helped cooling.  

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On 3/8/2019 at 3:03 PM, Oscar Avalle said:

Well, I share your pain! I own a M20C 1970. I had it since 2003 and my high CHTs, I particular #3 has always been a headache. I had readings similar to yours. I did everything! So let me walk through some of the things I did:

a) doghouse: I replaced my old doghouse and baffling with a new one. Results: marginal (slightly lower CHTs but still above 450)

B) baffling: I replaced all the baffles in particular around the cowling entrance. results: marginal

c) cowling mod: I changed the air inlet form (droopy nose was replaced with a newer looking model). Results: marginal

d) carburetor: you have to get a high fuel flow on take off (16.5 gal at least) to ensure cooling. I overhauled the carburetor and had it checked to make sure it was up to standards. Results: significant. First time CHT really changed for better. I still got 430 on number 3 but much better than 470.

e) technique: I applied a take off and climb procedure similar to the one described above, ensuring higher speed before climbing and playing with the throttle and RPM. Results: good, on average a 15 degree lower CHT

d) clean up inside cowling: you have to avoid having hoses interfering with the airflow inside the cowling. Results: marginal

e) cowlflaps: make sure that the cowlflaps aperture is large enough. Results: marginal

So my experience has been that (besides the carburetor and technique) there is no silver bullet but that all these measures help keeping the CHTs low.

I hope this helps you and does not get you even more confused.

Oscar





Sent from my iPhone using Tapatalk Pro

Thank you Oscar!  I am going to check most of that tomorrow.  I like the carburetor idea.  I can tolerate 430!  I feel 468 is way to high.  Again it comes down in cruise but just don't want to hurt the cylinders!

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7 hours ago, jaylw314 said:

Where do you see 14 gph?  The scanner display is showing 14.2 gallons used (USD), but I can't make out the actual gph.  @Pilotja5, do you have any bigger pictures of the display or data logs?

I don't have any bigger pictures yet!  I will get some next time I take it up.  the bottom half of the guppy mouth is closed off too!  Going out tomorrow to check the doghouse and if the weather clears, may take it up to see what the fuel flow is on takeoff.  Sounds like from here, there is a possibility of having a carburetor which is restricting fuel flow on takeoff.  I am definitely going to check the baffling and the doghouse and will take a better picture next time I fly!

 

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One item to check on the baffles is the rubber front lip where it goes into the channel on the inside of the front edge of the cowl opening. Many times I have seen that when the cowl is put back on this forward rubber lip is not in the channel it was designed to go in and when flown, air bypasses the entry into the top of the dog house and goes instead, around the dog house and out the bottom.  Closing all the holes around the starter bendix and generator is also needed

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20 hours ago, cliffy said:

Here's another great carb operation book to read

 

file:///C:/Users/72773/Downloads/MA-4%20Crab%20Operation%20Manual.pdf

Cliffy, Thank you for the information.  Is there anyway you can send me the manual. If needed, feel free to let me know and I can send you my email address.  

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Mooneyspacers!  Thank you for all the advice.  Went up last weekend, it looks like I do have the high flow carb!  on climbout, it is burning approximately 16 gph.  I also checked the doghouse, and there are some holes that needs to be sealed up.  I noticed a good bit of light coming through where the top of it bolts to the sides.  Has anyone used anything to seal that up?  I was thinking some kind of gasket material but wanted to see what everyone else had done.  Again, thank you everyone for the advice.  By the way, Cylinder 3 got up to 450 on climbout yesterday at 120mph and full throttle, 2500 rpm.  

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10 minutes ago, Pilotja5 said:

Mooneyspacers!  Thank you for all the advice.  Went up last weekend, it looks like I do have the high flow carb!  on climbout, it is burning approximately 16 gph.  I also checked the doghouse, and there are some holes that needs to be sealed up.  I noticed a good bit of light coming through where the top of it bolts to the sides.  Has anyone used anything to seal that up?  I was thinking some kind of gasket material but wanted to see what everyone else had done.  Again, thank you everyone for the advice.  By the way, Cylinder 3 got up to 450 on climbout yesterday at 120mph and full throttle, 2500 rpm.  

High Temp RTV is the most common sealant used to seal holes and cracks. 

Reading this thread of all the high CHTs in M20C reinforces the need for better cowling. The SabreCowl Gen 2 can't come too soon. @Sabremechbuilt the first SabreCowl for his own C. Reduce temps and increased speed. An it looks pretty good too. @AGL Aviationwill be offering the cowl as soon as it is ready. Stay tuned for details.

IMG_20190107_153647859_HDR.jpg

IMG_20190107_153600437_HDR.jpg

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11 minutes ago, cliffy said:

pilotja5-

The manual is downloadable and printable right on your computer. That's what I did.

Its more of an article than a book. I could have phrased it better. 

I will give it a try.  Thank you!

 

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12 minutes ago, cliffy said:

pilotja5-

The manual is downloadable and printable right on your computer. That's what I did.

Its more of an article than a book. I could have phrased it better. 

 

31 minutes ago, Hank said:

Try WOT/2700, 18gph, it should be cooler. 

I will try that Hank!   Yeah I am open to suggestions.  By the way, are your cowl flaps riveted in or adjustable?  Ours is fixed, and riveted.

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58 minutes ago, Bob_Belville said:

High Temp RTV is the most common sealant used to seal holes and cracks. 

Reading this thread of all the high CHTs in M20C reinforces the need for better cowling. The SabreCowl Gen 2 can't come too soon. @Sabremechbuilt the first SabreCowl for his own C. Reduce temps and increased speed. An it looks pretty good too. @AGL Aviationwill be offering the cowl as soon as it is ready. Stay tuned for details.

IMG_20190107_153647859_HDR.jpg

IMG_20190107_153600437_HDR.jpg

That is a great looking Cowl!  Yeah it is sounding like I am battling a typical battle.  That colw looks great!

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Just as a point of reference (and my 1 point CHT gauge) my D climbs at  @ 100-110  mph in 90 degree weather starting at 4300' to 9000-10,000 MSl and I  see about 400 degrees CHT.  Cooler days I run 380 or so. There is no need to tolerate high CHTs.  I've never seen 450. You have to tighten up the airbox and seal the alternator and starter holes in front. Make sure the front lip rubber seal is in good shape and entered into the channel it is supposed to be in when the cowl goes back on.   

Edited by cliffy
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8 minutes ago, cliffy said:

Just as a point of reference (and my 1 point CHT gauge) my D climbs at  @ 100-110  mph in 90 degree weather starting at 4300' to 9000-10,000 MSl and I  see about 400 degrees CHT.  Cooler days I run 380 or so. There is no need to tolerate high CHTs.  I've never seen 450. You have to tighten up the airbox and seal the alternator and starter holes in front. Make sure the front lip rubber seal is in good shape and entered into the channel it is supposed to be in when the cowl goes back on.   

I suspect CHTs were never such a concern on the C model until engine monitor use became widespread. At least it wasn't for me - the #3 cylinder where the factory probe is installed is often not the hottest one.  Also ~4300ft at 90F and standard barometric pressure means only about 80% HP at takeoff, which must help prevent overheating I would think - perhaps the only advantage of being based at high altitude.  No argument that the baffling is very important, but doing all the things you say took my cooling from horrible to merely just very bad.

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Well guys, I managed to get the temps down 30 degrees.  Used RTV silicone for all cracks and holes that I could in the baffling.  Then used some metal tape around the doghouse where it bolts down.  Flew it yesterday and the warmest cylinder was 428 degrees.  I am calling that a good win.  In cruise, they came right on down to the lower 300's.  Thank you everyone for the help.  I am sure there is a little more to do but at least it isn't cooking nearly as bad! 

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2 hours ago, Pilotja5 said:

 Flew it yesterday and the warmest cylinder was 428 degrees.  I am calling that a good win.  In cruise, they came right on down to the lower 300's.  Thank you everyone for the help.  I am sure there is a little more to do but at least it isn't cooking nearly as bad! 

It’s not a popular practice on the forums but consider pulling the power back some during the climb. I would rather have 380 temps for 12 mins vs 430 for 9.  By all means use the performance when you need it but don’t be afraid to dial it back. 

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You might want to read “Speed with Economy” by Kent Paser. He did a lot of work on his home built Mustang 2 to improve its performance.  Cooling efforts included sealing everything and trimming the Lycoming inter cylinder baffles to optimize in visual cylinder  cooling.

Clarence

http://www.eaa393.org/Presentations/ScotS_rev_SwEconomyKentPaser2006.pdf is a small excerpt.

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37 minutes ago, MIm20c said:

It’s not a popular practice on the forums but consider pulling the power back some during the climb. I would rather have 380 temps for 12 mins vs 430 for 9.  By all means use the performance when you need it but don’t be afraid to dial it back. 

I agree with Michigan man.  When I climb at WOT, my CHTs creep up to 420°.  When I climb at 25/25, they stay around 380-400.

More power produces more heat.  Extra fuel helps, but it doesn't change that fact.

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Additional data...

We see the same thing in more modern Mooneys with the extra pair of cylinders....

Departing WOT, 2700rpm, FF close to 30gph...

Climbing out at 120kias...

Scaling these numbers for a similar set for an O360 makes 20gph looks like a good way to use fuel for additional cooling...

If 18 is all you can get... it is better than 15...

+1 for getting real data. A decade of a single analog CHT was too little data for me... for a long time...

+1 for tightening up the old cowl. With real data, you will see results...

+1 for getting new rubber seals in place of the old fabric

+1 for the new cowl it has real airflow control, air comes in from above the cylinders... turns 90°, to go through the cooling fins... turns 90° again to escape out the cowl flaps.... the dog house is challenged on its best days to get the air, through, and out without leaking everywhere...

PP thoughts only, not a mechanic...

Best regards,

-a-

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