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RV-8 Cowl Vents

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japhillipsga(at)aol.com
Guest

Posted: Mon Aug 08, 2011 6:08 am Post subject: RV-8 Cowl Vents

Dear Fellow RV-8 Builders, I now have 13 hours on my 0360 Lyc. Still having # 1 CHT get too hot before TOC. So I have to throttle back and stairstep up to altitude. Temps should be stable by now with 13 hours. So I bought from Avery the bottom cowl louvers to improve airflow. Talked to a couple RV-8 drivers both said the vents lowered CHTs about 20 degrees. Question is how is best to mount?  What shape and size hole(s)? The bottom of the vent plate is flat while the cowl bottoms have compound curve surfaces. What is best for looks and effectiveness and strength? Hope to hear from someone, Bill of Georgia N288WP

 

   

 

 

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Matt Dralle
Site Admin

Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA

Posted: Mon Aug 08, 2011 9:53 am Post subject: RV-8 Cowl Vents

At 07:04 AM 8/8/2011  Monday, you wrote:

 	  Quote: 	
		  Dear Fellow RV-8 Builders, I now have 13 hours on my 0360 Lyc. Still having # 1 CHT get too hot before TOC. So I have to throttle back and stairstep up to altitude. Temps should be stable by now with 13 hours. So I bought from Avery the bottom cowl louvers to improve airflow. Talked to a couple RV-8 drivers both said the vents lowered CHTs about 20 degrees. Question is how is best to mount?  What shape and size hole(s)? The bottom of the vent plate is flat while the cowl bottoms have compound curve surfaces. What is best for looks and effectiveness and strength? Hope to hear from someone, Bill of Georgia N288WP


	


Hi Bill,



I have an IO-390 210hp on my RV-8 with the standard cowling.  I don't have any trouble with CHT's (generally well under 400f) and my oil temps are generally in the low 180'sf.  If I take off on a hot day at sea level and climb hard, I can get the CHT on the hot cylinder to go over 400 but by that time I'm at 8000 ft and simply decreasing my angle slightly will bring it back down.  The only "non-stock" aspect of my installation is the giant oil cooler I added to the back of the baffle.  Its about twice the size of the stock one.  



Before you start cutting holes in your cowling, you might want to do some more investigation into the cause of the overheating.  Might be indicative of something else.  Plugged oil line to that cylinder, maybe a blocked fuel injector on that cylinder?  Try swapping the injectors between the hottest and coolest cylinder and see what impact this has on the CHT.



Here's some info on the oil cooler installation that has worked well for me:



        http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2972&log=90253&row=84



Matt

-

Matt Dralle

RV-8 #82880 N998RV "Ruby Vixen"

http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log

http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log

http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel

Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...

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Matt Dralle
Matronics Email List Administrator

n223rv(at)wolflakeairport
Guest

Posted: Mon Aug 08, 2011 2:28 pm Post subject: RV-8 Cowl Vents

Bill,



Do you have the wheel pants and gear leg fairings installed?  If not, I would not make any drastic changes until you get them installed.  They will speed your plane up and provide less drag, of which you will get more airflow and less engine work.



Sent from my iPhone



On Aug 8, 2011, at 1:47 PM, Matt Dralle <dralle(at)matronics.com> wrote:



 	  Quote: 	
		   

 

 At 07:04 AM 8/8/2011  Monday, you wrote:

> Dear Fellow RV-8 Builders, I now have 13 hours on my 0360 Lyc. Still having # 1 CHT get too hot before TOC. So I have to throttle back and stairstep up to altitude. Temps should be stable by now with 13 hours. So I bought from Avery the bottom cowl louvers to improve airflow. Talked to a couple RV-8 drivers both said the vents lowered CHTs about 20 degrees. Question is how is best to mount?  What shape and size hole(s)? The bottom of the vent plate is flat while the cowl bottoms have compound curve surfaces. What is best for looks and effectiveness and strength? Hope to hear from someone, Bill of Georgia N288WP

 

 Hi Bill,

 

 I have an IO-390 210hp on my RV-8 with the standard cowling.  I don't have any trouble with CHT's (generally well under 400f) and my oil temps are generally in the low 180'sf.  If I take off on a hot day at sea level and climb hard, I can get the CHT on the hot cylinder to go over 400 but by that time I'm at 8000 ft and simply decreasing my angle slightly will bring it back down.  The only "non-stock" aspect of my installation is the giant oil cooler I added to the back of the baffle.  Its about twice the size of the stock one.  

 

 Before you start cutting holes in your cowling, you might want to do some more investigation into the cause of the overheating.  Might be indicative of something else.  Plugged oil line to that cylinder, maybe a blocked fuel injector on that cylinder?  Try swapping the injectors between the hottest and coolest cylinder and see what impact this has on the CHT.

 

 Here's some info on the oil cooler installation that has worked well for me:

 

        http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2972&log=90253&row=84

 

 Matt

 

 

 -

 Matt Dralle

 RV-8 #82880 N998RV "Ruby Vixen"

 http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log

 http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log

 http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel

 Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...

robin(at)PaintTheWeb.com
Guest

Posted: Mon Aug 08, 2011 2:41 pm Post subject: RV-8 Cowl Vents

That was our experience exactly (8A) but with oil temps, our CHT's were fine. Wheel pants & leg fairings added about 14 knots and reduced our oil temps about 15 degrees.



Robin

Do Not Archive

 

On Mon, Aug 8, 2011 at 3:25 PM, Michael Kraus <n223rv(at)wolflakeairport.net (n223rv(at)wolflakeairport.net)> wrote:

[quote] --> RV8-List message posted by: Michael Kraus <n223rv(at)wolflakeairport.net (n223rv(at)wolflakeairport.net)>

 

 Bill,

 

 Do you have the wheel pants and gear leg fairings installed?  If not, I would not make any drastic changes until you get them installed.  They will speed your plane up and provide less drag, of which you will get more airflow and less engine work.

  

 Sent from my iPhone

 



 On Aug 8, 2011, at 1:47 PM, Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)> wrote:

 

 > --> RV8-List message posted by: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>

 >

 > At 07:04 AM 8/8/2011  Monday, you wrote:

 >> Dear Fellow RV-8 Builders, I now have 13 hours on my 0360 Lyc. Still having # 1 CHT get too hot before TOC. So I have to throttle back and stairstep up to altitude. Temps should be stable by now with 13 hours. So I bought from Avery the bottom cowl louvers to improve airflow. Talked to a couple RV-8 drivers both said the vents lowered CHTs about 20 degrees. Question is how is best to mount?  What shape and size hole(s)? The bottom of the vent plate is flat while the cowl bottoms have compound curve surfaces. What is best for looks and effectiveness and strength? Hope to hear from someone, Bill of Georgia N288WP

  >

 > Hi Bill,

 >

 > I have an IO-390 210hp on my RV-8 with the standard cowling.  I don't have any trouble with CHT's (generally well under 400f) and my oil temps are generally in the low 180'sf.  If I take off on a hot day at sea level and climb hard, I can get the CHT on the hot cylinder to go over 400 but by that time I'm at 8000 ft and simply decreasing my angle slightly will bring it back down.  The only "non-stock" aspect of my installation is the giant oil cooler I added to the back of the baffle.  Its about twice the size of the stock one.

  >

 > Before you start cutting holes in your cowling, you might want to do some more investigation into the cause of the overheating.  Might be indicative of something else.  Plugged oil line to that cylinder, maybe a blocked fuel injector on that cylinder?  Try swapping the injectors between the hottest and coolest cylinder and see what impact this has on the CHT.

  >

 > Here's some info on the oil cooler installation that has worked well for me:

 >

 >        http://www.mattsrv8.com/users/display_log.php?user=MattsRV8&project=638&category=2972&log=90253&row=84

  >

 > Matt

 >

 >

 > -

 > Matt Dralle

 > RV-8 #82880 N998RV "Ruby Vixen"

 > http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log

 > http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log

 > http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel

 > Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...

 >

 >

 >

 >

 >

 

 

 ===========

 rget="_blank">http://www.matronics.com/Navigator?RV8-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 



[b]

japhillipsga(at)aol.com
Guest

Posted: Mon Aug 08, 2011 4:01 pm Post subject: RV-8 Cowl Vents

Thanks fellows, the engine is new and only has 13 hours on it. I am still working on the damned intersections and pants, etc. I appreciate the advise not to install the louver vents until I see how she does with the undercarriage clean, Makes good sense, Bill

  

     

  

    

     

  

     

  

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Speedy11(at)aol.com
Guest

Posted: Tue Aug 09, 2011 7:35 pm Post subject: RV-8 Cowl Vents

Bill,

 I sure agree with Matt on this subject.  I would investigate other  causes for the high CHT before cutting up the cowling.  I would cut the  cowling only if all CHTs were too high.

 His ideas are good ones and you also might try swapping the #1 and #3 CHT  probes.  Maybe #1 is reading high.

 It is very odd that #1 cylinder would be your hot one.  Did you add an  air dam in front of it?  If so, have you tried different size  dams?   Or removing the air dam?

  

 Stan Sutterfield

 Do not archive

  

 In a message dated 8/9/2011 3:09:02 A.M. Eastern Daylight Time,  rv8-list(at)matronics.com writes:

  	  Quote: 	
		  Before    you start cutting holes in your cowling, you might want to do some    more

investigation into the cause of the overheating.  Might be    indicative of something

else.  Plugged oil line to that cylinder,    maybe a blocked fuel injector on

that cylinder?  Try swapping the    injectors between the hottest and coolest cylinder

and see what impact this    has on the CHT.



	


 

  

  [quote][b]

japhillipsga(at)aol.com
Guest

Posted: Tue Aug 09, 2011 8:09 pm Post subject: RV-8 Cowl Vents

Stan, I tested the CHT probes and they are correct. I have the standard Van's baffle wind dam in front of # 1 Cylinder. I trimmed about 5/8th inch off the top and noted a small drop in CHT tempt, but it did not even out with the other three jugs. I'll just not worry about it until after I get the wheel pants and leggings all installed. Thanks for the help, Bill

  

     

  

    

     

  

     

  

    --

Matt Dralle
Site Admin

Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA

Posted: Wed Aug 10, 2011 8:30 am Post subject: RV-8 Cowl Vents

Oh, my...  I missed the part where you had installed the air dam baffle in front of #1!  Get rid of that completely.  The Baffle Plans say to start *without* this baffle and then add it IF #1 is running too cool.  I never installed this air dam and have never had any problems with #1.  



Matt



-

Matt Dralle

RV-8 #82880 N998RV "Ruby Vixen"

http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log

http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log

http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel

Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap...

At 09:06 PM 8/9/2011  Tuesday, you wrote:

[quote]Stan, I tested the CHT probes and they are correct. I have the standard Van's baffle wind dam in front of # 1 Cylinder. I trimmed about 5/8th inch off the top and noted a small drop in CHT tempt, but it did not even out with the other three jugs. I'll just not worry about it until after I get the wheel pants and leggings all installed. Thanks for the help, Bill



--

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Matt Dralle
Matronics Email List Administrator

japhillipsga(at)aol.com
Guest

Posted: Wed Aug 10, 2011 12:44 pm Post subject: RV-8 Cowl Vents

Matt, I'll do that before I fly again. BTW  How is the rebuild coming? We all expect to see her better and 

   faster than before. Thanks, Bill

 

 

   

 

 

   --

Matt Dralle
Site Admin

Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA

Posted: Wed Aug 10, 2011 5:55 pm Post subject: RV-8 Cowl Vents

The rebuild is coming alone nicely.  Definitely going faster the second time.  I'm shooting to re-test fly in the Spring.  Just getting ready to start the wiring this weekend.  With the wiring complete, how much more could there be?  <smirk>



Matt

At 01:40 PM 8/10/2011  Wednesday, you wrote:

[quote]Matt, I'll do that before I fly again. BTW  How is the rebuild coming? We all expect to see her better and 

faster than before. Thanks, Bill



--

_________________
Matt Dralle
Matronics Email List Administrator

Speedy11(at)aol.com
Guest

Posted: Wed Aug 10, 2011 7:07 pm Post subject: RV-8 Cowl Vents

Bill,

 I initially flew my RV with no dam in front of #1 cylinder.  It was  running about 30 degrees cooler than the others so I added a "ski ramp" air dam  that is easily replaced.  I can try different shapes and sizes until I get  the temp just right.  I've never liked the blunt, brute force air dams  placed in front of cylinders, so I made a more aerodynamic, easily replaceable,  easily modified air dam.  You can see a photos and comments at http://www.rv-8a.net/2009Jul.htm and  http://www.rv-8a.net/2010Jun.htm

  

 Stan Sutterfield

  

 In a message dated 8/10/2011 3:07:05 A.M. Eastern Daylight Time,  rv8-list(at)matronics.com writes:

  	  Quote: 	
		  I tested    the CHT probes and they are correct. I have the standard Va

n's baffle wind    dam in front of # 1 Cylinder. I trimmed about 5/8th inch of

f the top and    noted a small drop in CHT tempt, but it did not even out with

the other    three jugs. I'll just not worry about it until after I get the w

heel pants    and leggings all installed. 	


 

  

  [quote][b]

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