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  #1  
Old 10-23-2019, 08:09 AM
ALagonia ALagonia is offline
 
Join Date: Jul 2017
Posts: 344
Default CHT temps and a plenum

Would like to hear from those 9 drivers that have an O-360 with a plenum and a FP prop. I have a three blade Catto.
How did you deal with high CHT temps? Not higher than Lycoming recommended limits but would like to lower temps if possible without flying at a lower HP.
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  #2  
Old 10-23-2019, 10:56 AM
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Aviaman Aviaman is offline
 
Join Date: Feb 2018
Location: Louisville KY
Posts: 95
Default CHT Plenum

I have a -9A with the James plenum and Cato 3 blade prop.
I implemented solutions to the ?zero fin depth? problem with Lycoming cylinders. There is a lot about that on other threads. I modified the air box to have channels passing air around the 0 fin depth area.
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Cessna 170B-sold
Zenith 601XL-sold
Vans RV-6 slider-sold
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O-360, AFS EFIS, True-track autopilot, Garmin GDL-82 ADS-B, Garmin 327 Transponder, Garmin 496

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  #3  
Old 10-23-2019, 11:00 AM
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Aviaman Aviaman is offline
 
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Location: Louisville KY
Posts: 95
Default CHTS plenum

I got about 20 degrees F lowering of CHTs on cylinders 2 and 3 where I made the mod.
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Cessna 170B-sold
Zenith 601XL-sold
Vans RV-6 slider-sold
Vans RV-9A slider, flying
O-360, AFS EFIS, True-track autopilot, Garmin GDL-82 ADS-B, Garmin 327 Transponder, Garmin 496

Dues happily paid Jan 3, 2020
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  #4  
Old 10-23-2019, 11:57 AM
ALagonia ALagonia is offline
 
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Default

Quote:
Originally Posted by Aviaman View Post
I got about 20 degrees F lowering of CHTs on cylinders 2 and 3 where I made the mod.
Can you explain the mod? Any pictures?
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  #5  
Old 10-23-2019, 06:56 PM
gmkonrad gmkonrad is offline
 
Join Date: Feb 2005
Location: Howell,MI
Posts: 132
Default Hot #3 CHT - Solved!

Search VAF for : Hot #3 CHT - Solved!

Gary
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  #6  
Old 10-23-2019, 08:48 PM
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N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,887
Default

I have a two bladed Catto in front of a Sam James cowl and plenum that hides an O-360.

Setting the timing correctly helped lower my CHT's.

However, I think the problem with most plenums is that the builders tend to set them as low to the cylinders as they can. This is wrong. You want to give the air space to slow down before going past the cylinders. If you are still working on yours, get it as up high as you can.
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RV-9 (Yes, it's a dragon tail)
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  #7  
Old 10-23-2019, 09:03 PM
sibriggs sibriggs is offline
 
Join Date: Nov 2014
Location: Concord, NH
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Default What I did

Early in my RV9 time, my temps hit the 400+ range during climb out.
I did two things.
1- added cowl flaps, that dropped the temps 20+ degrees F.
2- changed my engine management, leave it full rich on climb to 6k or 8k or what ever your cruise is going to be.

Now I never see temps over 385 to 390F and cruise in the 320-350F range.

IO320 with GA prop set to high cruise pitch.
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  #8  
Old 10-23-2019, 09:26 PM
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N941WR N941WR is offline
 
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Location: SC
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Quote:
Originally Posted by sibriggs View Post
Early in my RV9 time, my temps hit the 400+ range during climb out.
I did two things.
1- added cowl flaps, that dropped the temps 20+ degrees F.
2- changed my engine management, leave it full rich on climb to 6k or 8k or what ever your cruise is going to be.

Now I never see temps over 385 to 390F and cruise in the 320-350F range.

IO320 with GA prop set to high cruise pitch.
The question is, what is high temperatures?

Lycoming lists 435*F as the max continuous and 500 as the max temperature.

If your CHT's go over 400*F in climb don't worry about them. The idea is to have less than 400*F in cruise.
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RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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  #9  
Old 10-24-2019, 05:39 AM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 296
Default

Bill R said: "You want to give the air space to slow down before going past the cylinders. "

Please clarify that statement as I understand attaining "Reynolds Number Velocity" is essential to creating turbulence in between the fins necessary to maximize heat transfer.
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  #10  
Old 10-24-2019, 05:45 AM
ALagonia ALagonia is offline
 
Join Date: Jul 2017
Posts: 344
Default

Quote:
Originally Posted by N941WR View Post
The question is, what is high temperatures?

Lycoming lists 435*F as the max continuous and 500 as the max temperature.

If your CHT's go over 400*F in climb don't worry about them. The idea is to have less than 400*F in cruise.
The highest I?ve seen in climb is 428 on cylinder #4. In cruise I?m right at or right under 400 on cylinder #4. All others are lower.
I do keep the mixture full rich in a climb. And my fuel flow at take off is 15.3 gph.
I listened to the EAA webinar on leaning last night and getting CHT?s too low is not desirable. I would like to see mine a little closer to each other. I?ve been able to balance them out a bit and lower #4 experimenting with aluminum tape on cylinders 1 and 2 but at the expense of higher CHT?s on 1,2 and 3.
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