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  #21  
Old 09-06-2018, 09:29 AM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
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Quote:
Originally Posted by Robb View Post
I guess this is what you have to deal with on experimental airplanes.
No, you don't. Quite the opposite. With an experimental we are free to make whatever changes we wish to improve cooling performance. Of course, the two-edged sword rule applies; we're equally free to make bad choices.
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RV-8 SS
Barrett IO-390

Last edited by DanH : 10-04-2018 at 11:34 AM.
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  #22  
Old 10-14-2018, 11:52 PM
rightrudder rightrudder is offline
 
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Location: Laguna Hills, CA
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I finished the baffle modifications for cylinders 2 & 3 (quite similar to the pic that BillL posted) and am extremely happy with the results. No. 2 (the hottest) dropped about 25 degrees and is now the coolest! No. 3 is down about 10 degrees. Shoulda done this sooner.
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RV-9A "slider"--sold in July 2021
Flew to Osh in 2017, 2018 & 2019!
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  #23  
Old 10-15-2018, 06:37 AM
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NYTOM NYTOM is offline
 
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Location: Raleigh, North Carolina
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Just finished the #2 cylinder mod as presented by Bill and also having completed the widely accepted modification duct on #4. Glad to hear your results were acceptable Doug. Confident I have avoided a potential overheating problem. Would never have know about these proven solutions if not for the ?VAF? Thank you gentelmen.
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Classic "Short Tail 6A N822PM
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  #24  
Old 10-30-2018, 12:46 PM
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boom3 boom3 is offline
 
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Does anyone have any pictures of successful baffling improvements for cylinder #4? I've seen lot's of great ideas for #2 and #3. Thanks!

IO-360 parallel valve, Van's baffling with stock oil cooler.
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  #25  
Old 06-18-2019, 01:51 PM
bizpilot bizpilot is offline
 
Join Date: Sep 2015
Location: Falmouth Airpark, Mass (Cape Cod area)
Posts: 48
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I know this thread has been extensively discussed last fall, but I have a different question. Our RV14A IO390 runs cold. Typically front cylinders 1and 2 low 200’s CHT’s, rear’s 3 and 4 mid to upper 200’s. This is at cruise. Almost never see 300 CHT’s. The CHT input curves were switched in our G3X from K to J or vice versa (can’t remember) then the CHT’s look normal. The ones with the cold numbers were the correct for our installation.
Any input appreciated.
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  #26  
Old 06-19-2019, 12:31 PM
N54SG N54SG is offline
 
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Location: Kansas City, MO
Posts: 127
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Quote:
Originally Posted by bizpilot View Post
I know this thread has been extensively discussed last fall, but I have a different question. Our RV14A IO390 runs cold. Typically front cylinders 1and 2 low 200’s CHT’s, rear’s 3 and 4 mid to upper 200’s. This is at cruise. Almost never see 300 CHT’s. The CHT input curves were switched in our G3X from K to J or vice versa (can’t remember) then the CHT’s look normal. The ones with the cold numbers were the correct for our installation.
Any input appreciated.
Highly suspect in my opinion. Type K thermocouple wire must not be mixed with Type J. The correct wire must be used with the correct probe, then configured properly in the G3X. Wire color is the easy way to tell which you have. Read this builders note from SteinAir:

http://www.steinair.com/wp-content/u...uple-cable.pdf

Wire:
https://www.steinair.com/product-cat.../thermocouple/

Also, I recently learned there are some grounded and ungrounded CHT probes. If I remember correctly, Advanced Flight Systems used ungrounded Type J CHT probes. Those WILL NOT work with a G3X. I had to change out 4 probes on a recent build to Grounded Type J (so I could use all my existing wiring behind the panel) and that corrected the false indication.

Low 200's at any power setting other than idle, in the winter, doesn't seem possible.
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  #27  
Old 03-18-2020, 06:40 PM
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gmcjetpilot gmcjetpilot is offline
 
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Quote:
Originally Posted by N942R View Post
On those I have mounted the oil coolers on a NACA duct on the "Right side" of the cowl which will solve that problem.. Nothing wrong with the coolers... But that is a separate issue.
Submerged NACA ducts are problematic for an oil cooler, many test, experience, articles has shown this success is not automatic with a NACA scoop. Love to see your whole NACA oil cooler set up.

1) NACA - you can also cause overheating by pressurizing the lower cowl with your NACA scoop if the oil cooler is dumping air back inside the lower cowl.

2) NACA can flow volume when there is little to no resistance and lower pressure at discharge. Dave Anders wrote an article in Kit plane (Oct 2018 Optimizing Induction Air Fine-tuning intake system runners for increased performance and economy. Speed with Economy, Kent Paser wrote about NACA scoops more enthusiastically in his classic book. However they are not magic and often implemented, located and used incorrectly. They always look "cool" but they are no free lunch. They do add drag and may produce very little airflow unless you do everything correctly. You might be better off with an external scoop and take the drag and get real RAM Pressure, with a discharge separate from lower cowl plenum. Many planes like the DC-3 has the oil cowl completely outside the cowl. The cooler needs high delta P to flow air and NACA scoops don't create pressure but flow air, at lower pressure head. Add back pressure on the exit side of the cooler inside cowl you may end up with no flow or reverse flow.

http://www.vansairforce.com/communit...ead.php?t=5551

http://www.vansairforce.com/communit...ad.php?t=97016


Car guys also debate the Scoop vs (submerged) NACA
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2023 Donation Made!

Last edited by gmcjetpilot : 03-18-2020 at 06:50 PM.
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  #28  
Old 08-15-2022, 09:05 PM
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petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,338
Default Do I have Recovery? Pressure Recovery.....

After a lot of hours, I'm taking a new look at my cowl and engine cooling. I had stock baffles for the first few years, then I made a bad plenum that has worked fine for many hours, but I never knew if it worked well. I know the seal at the inlets was not great and the FAB to cowl seal was not great either, but I know both can be improved...... My only real complaint is full power ROP climbs get the back two cylinders to 425 quickly before I pull back(on the rare occasion that I do it)

Following the teachings of Professor Horton, I made piccolo tubes and found a cheap used digital manometer - then I got some data tonight, allowing me to ask the question:

"Do I have recovery" What say you cowl doctors? The cowl needs some rework after 2600 hours, so maybe this winter I cut some fiberglass.....

Here is the cockpit setup running in diff pressure mode. I took some data comparing the upper and lower to ambient cockpit pressure, and the diff was same as the diff pressure on the screen.



Here is the data and a graph (all data @ 3000ft)


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Amateur Plane - RV-9A N789PH - 2650+ Hrs
Amateur Radio - KD0CVN
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Last edited by petehowell : 08-16-2022 at 07:03 AM.
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  #29  
Old 08-15-2022, 09:59 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by petehowell View Post
"Do I have recovery" Here is the cockpit setup running in diff pressure mode. I took some data comparing the upper and lower to ambient cockpit pressure, and the diff was same as the diff pressure on the screen.
Hi Pete. Yes, you have recovery. The question is how much, specifically the percentage of available dynamic pressure converted to upper plenum static pressure. DeltaP across the baffles doesn't help us; we need upper plenum deltaP vs freestream static. I tap the aircraft static system for freestream static.

So, easy as 1-2-3...

1. List upper plenum static vs freestream static deltaP for each airspeed.

2. Compute available freestream dynamic pressure for each airspeed and convert it to inches of water.

(There is an excellent online calculator here: http://www.aerospaceweb.org/design/scripts/atmosphere/ Don't neglect the temperature correction, plus or minus standard day temperature for that altitude. 25C would be a +14 above standard for 3000 ft.)

3. Divide upper plenum static by freestream dynamic. Good systems are generally above 0.8.

It's very hard to fly a specific true airspeed, for example, exactly 150 KTAS. It's a lot easier and more accurate to fly a NTPS 3-leg while collecting the pressure information. That way you have an exact airspeed for each data point, thus a precise dynamic pressure.

Illustration below from NASA CR3405.
.
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Last edited by DanH : 08-15-2022 at 10:18 PM.
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  #30  
Old 08-15-2022, 10:25 PM
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petehowell petehowell is offline
 
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Location: MN
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Default More data

**** - I have to fly again..... Thanks for the input, I'll tap the static and get the data!

Quote:
Originally Posted by DanH View Post
Hi Pete. Yes, you have recovery. The question is how much, specifically the percentage of available dynamic pressure converted to upper plenum static pressure. DeltaP across the baffles doesn't help us; we need upper plenum deltaP vs freestream static. I tap the aircraft static system for freestream static.

So, easy as 1-2-3...

1. List upper plenum static vs freestream static deltaP for each airspeed.

2. Compute available freestream dynamic pressure for each airspeed and convert it to inches of water.

(There is an excellent online calculator here: http://www.aerospaceweb.org/design/scripts/atmosphere/ Don't neglect the temperature correction, plus or minus standard day temperature for that altitude. 25C would be a +14 above standard for 3000 ft.)

3. Divide upper plenum static by freestream dynamic. Good systems are generally above 0.8.

It's very hard to fly a specific true airspeed, for example, exactly 150 KTAS. It's a lot easier and more accurate to fly a NTPS 3-leg while collecting the pressure information. That way you have an exact airspeed for each data point, thus a precise dynamic pressure.

Illustration below from NASA CR3405.
.
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Amateur Plane - RV-9A N789PH - 2650+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN
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