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BobbyPaulk(at)comcast.net
Guest

Posted: Thu Dec 18, 2008 6:47 am Post subject: Engine Cooling

List,

i have the 601 XL with 3300 Jabiru & original fiberglass ram air ducts. i have cut and modified the ram air ducts, added little dams and even increased the size on one side to compare with the other. my back two cylinders are still running 335 - 345 at cruise power settings. at max power 5 & 6 hit 356 at a 600' climb from near sea level.  the other four cyl. are 300 or under. my question is - has anyone used the old style Lyc. or Cont. baffeling that has worked for a hundred years and got better CHT's on Cyl. 5 & 6. 

i am thinking of trying the Sonex type of baffles. anybody got a clue. 



bobby

70 hrs and still fixin stuff

rpf(at)wi.rr.com
Guest

Posted: Thu Dec 18, 2008 1:21 pm Post subject: Engine Cooling

Bobby,



Did you epoxy a little deflector above the rear cylinders (actually above 

the rear and middle cylinders) like Jabiru USA advises?  I have the same 

setup as you and all my cylinders run under 300 degrees.  Even when I flew 

out west to visit my brother with temperatures approaching 100 degrees.



Randy

601xl, Jab 3300, 235hours

---

amyvega2005(at)earthlink.
Guest

Posted: Fri Dec 19, 2008 7:21 am Post subject: Engine Cooling

sounds likre the baffles over the back cylinders are not pushing enough air through into the cilinder vents.  the deflection peice should go from the top of the duct to block off all air from flowing over the top of the cilinder but down through the cooling vents.  use some metal and fit to cut so there is no room hardly for air to gow over but only through the cilinder cooling vents.

Or your temperature sensor is off.  



Juan



--

DaveG601XL

Joined: 27 Oct 2006
Posts: 351
Location: Cincinnati, Oh

Posted: Fri Dec 19, 2008 10:38 am Post subject: Re: Engine Cooling

Bobby,



I am in the same boat as you.  I have played with my baffles some, but still get warm temperatures in the back cylinders.  Within limits, sure, but it would be better to have a more even distribution.  #1-#4 are in the 280's to 300's F and the back ones see 350's F.



If you find the holy grail, let me know.  I will play with this some more next spring and summer.



Good luck,

_________________
David Gallagher
Cincinnati, OH area

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Fri Dec 19, 2008 10:46 am Post subject: Re: Engine Cooling

Bobby,



Be sure not to over look the exit.

All the intake in the world won't do you any good if it has nowhere to go.

Try to "suck" the cooling through.



I have seen studies that say the intake is far less important than the exhaust side of the cooling system.



Also be sure you oil cooler is getting fresh air.

the oil cooler is at least as important because it is an integral part of the whole cooling picture.



Just food for thought.

Good luck.

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

jaybannist(at)cs.com
Guest

Posted: Fri Dec 19, 2008 10:56 am Post subject: Engine Cooling

I can't remember where I read it, but the prevailing thought was that the cooling air outlet area needs to be 2 or 3 times the inlet area.

 

 Jay in Dallas

 

   

 

   

 

 --

dbrown(at)avecc.com
Guest

Posted: Fri Dec 19, 2008 12:42 pm Post subject: Engine Cooling

I had the same problem and also tinkered with the baffles.  However, Jabiru on their web site shows how to extend the bottom of the cowl depending on the extent of your problem. I riveted a .025 aluminum strip, one inch extension on lip of the cowl. Problem solved.



David  N601EX

tjs22t(at)verizon.net
Guest

Posted: Fri Dec 19, 2008 1:21 pm Post subject: Engine Cooling

Bobby,

  

 Aside from what's has been said about the baffles  between the cylinders AND the deflectors in the RamDucts just ahead of cylinders  5 and 6; keep in mind that the lower the pressure in the bottom portion  of the cowl the greater the airflow down through the heads.  To do this  make sure that the front of the air intakes to the ducts through the cowling  have NO (or as little as possible) air leaking under cylinders 1 and 2 and thus  into the bottom of the cowl (pics attached).  Also, the air coming into the  oil cooler through its duct/intake should ONLY go through the oil cooler.   Any air leaking around the the edges of the intake greatly, greatly defeats your  low pressure area in the lower cowl.  The difference in pressure between  the top and bottom cowling segments is as important as total exit area at the  rear of the bottom cowl lip.

  

 tailwinds  jeff HDS/3300 (no CHTs over  285F)

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pete(at)usjabiru.com
Guest

Posted: Fri Dec 19, 2008 2:13 pm Post subject: Engine Cooling

Attached is the procedure for installing cooling ducts from the Jabiru manual available on the Jabiru Australian web site.  We do block off the air from going in the bottom cowl but use a vertical air dam instead of the horizontal pieces that Jeff used.  

   

Jabiru makes the dam from fiberglass but there is no reason that scrap aluminum sheet if Zenith builders don’t want to mess with the fiberglass.  

   

Pete  

       

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of THOMAS SMALL

 Sent: Friday, December 19, 2008 4:43 PM

 To: zenith-list; BobbyPaulk(at)comcast.net

 Subject: Re: Engine Cooling  

  

  

     

Bobby,  

    

   

    

Aside from what's has been said about the baffles between the cylinders AND the deflectors in the RamDucts just ahead of cylinders 5 and 6; keep in mind that the lower the pressure in the bottom portion of the cowl the greater the airflow down through the heads.  To do this make sure that the front of the air intakes to the ducts through the cowling have NO (or as little as possible) air leaking under cylinders 1 and 2 and thus into the bottom of the cowl (pics attached).  Also, the air coming into the oil cooler through its duct/intake should ONLY go through the oil cooler.  Any air leaking around the the edges of the intake greatly, greatly defeats your low pressure area in the lower cowl.  The difference in pressure between the top and bottom cowling segments is as important as total exit area at the rear of the bottom cowl lip.  

    

   

    

tailwinds  jeff HDS/3300 (no CHTs over 285F)

Cooling_Duct_Installation.pdf

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dbrown(at)avecc.com
Guest

Posted: Fri Dec 19, 2008 2:50 pm Post subject: Engine Cooling

Here is the one I was referring to.



Jabiru Service Bulletin JSB 016

http://www.jabiru.net.au/Service%20Bulletins/Engine%20files/Engine%20Coo

ling%20JSB016-1.pdf

hills(at)sunflower.com
Guest

Posted: Fri Dec 19, 2008 3:44 pm Post subject: Engine Cooling

Don’t forget, the air picks up heat and expands after entering the cooling intake, hence the exhaust hole in the cowling must be larger than the cooling intake hole.  

   

Roger  

   

         

  

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of jaybannist(at)cs.com

 Sent: Friday, December 19, 2008 12:55 PM

 To: zenith-list(at)matronics.com

 Subject: Re: Re: Engine Cooling  

  

     

I can't remember where I read it, but the prevailing thought was that the cooling air outlet area needs to be 2 or 3 times the inlet area.

 

 Jay in Dallas  

    

   

    

   

  

-----Original Message-----

 From: Brady <brady(at)magnificentmachine.com>

 To: zenith-list(at)matronics.com

 Sent: Fri, 19 Dec 2008 12:46 pm

 Subject: Re: Engine Cooling   	  Quote: 	
		  --> Zenith-List message posted by: "Brady" <brady(at)magnificentmachine.com (brady(at)magnificentmachine.com)>

 

 

 

 Bobby,

 

 

 

 Be sure not to over look the exit.

 

 All the intake in the world won't do you any good if it has nowhere to go.

 

 Try to "suck" the cooling through.

 

 

 

 I have seen studies that say the intake is far less important than the exhaust 

 

 side of the cooling system.

 

 

 

 Also be sure you oil cooler is getting fresh air.

 

 the oil cooler is at least as important because it is an integral part of the 

 

 whole cooling picture.

 

 

 

 Just food for thought.

 

 Good luck.

 

 

 

 --------

 

 Brady McCormick

 

 Poulsbo, WA

 

 www.magnificentmachine.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 	


       size=2 width="100%" align=center>  

  

Email message sent from CompuServe - visit us today at http://www.cs.com  

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Afterfxllc(at)aol.com
Guest

Posted: Fri Dec 19, 2008 10:09 pm Post subject: Engine Cooling

Brady

  

 With all due respect, how many aircraft have you built? You are starting to  be the WW of the Zenith list. I think you are a smart guy and like what you are  trying to do but wouldn't it be better to have built at least 1 airplane before  you hand out answers to others problems? Having worked on a Jab that overheats  it is a pain in the ass engine when it comes to cooling. Jab will tell you they  don't have a problem but I have seen too many posts about overheating to believe  that. 

  

 BTW if the intake is small where is it going to "Suck" the air from? The  Jab uses small deflectors inside the baffles and if they are too big or small  the rear cylinder will overheat.

  

 Jeff

  

  

  

  

 Bobby,



Be sure not to over look the exit.

All the intake in the  world won't do you any good if it has nowhere to go.

Try to "suck" the  cooling through.



I have seen studies that say the intake is far less  important than the exhaust side of the cooling system.



Also be sure you  oil cooler is getting fresh air.

the oil cooler is at least as important  because it is an integral part of the whole cooling picture.



Just food  for thought.

Good luck.

 

  



One site keeps you connected to all your email: AOL Mail, Gmail, and Yahoo Mail. Try it now.

  [quote][b]

hills(at)sunflower.com
Guest

Posted: Sat Dec 20, 2008 5:53 am Post subject: Engine Cooling

Jeff;  

   

It is always better to have built “one airplane” before advising folks on their airplane problems, or for that matter, 10 airplanes. But skills in cutting metal and driving rivets has little to do with intellectual skills such as analyzing studies and applying knowledge to abstract problems such as thermal conduction (that’s what engineers do).  

Take it easy on Brady, he is on the right track and just trying to help (no good deed goes unpunished !!!!)  

   

Roger  

    

   

         

  

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of Afterfxllc(at)aol.com

 Sent: Saturday, December 20, 2008 12:08 AM

 To: zenith-list(at)matronics.com

 Subject: Re: Re: Engine Cooling  

  

       

Brady  

    

   

    

With all due respect, how many aircraft have you built? You are starting to be the WW of the Zenith list. I think you are a smart guy and like what you are trying to do but wouldn't it be better to have built at least 1 airplane before you hand out answers to others problems? Having worked on a Jab that overheats it is a pain in the ass engine when it comes to cooling. Jab will tell you they don't have a problem but I have seen too many posts about overheating to believe that.   

    

   

    

BTW if the intake is small where is it going to "Suck" the air from? The Jab uses small deflectors inside the baffles and if they are too big or small the rear cylinder will overheat.  

    

   

    

Jeff  

    

   

    

   

    

   

    

   

    

Bobby,

 

 Be sure not to over look the exit.

 All the intake in the world won't do you any good if it has nowhere to go.

 Try to "suck" the cooling through.

 

 I have seen studies that say the intake is far less important than the exhaust side of the cooling system.

 

 Also be sure you oil cooler is getting fresh air.

 the oil cooler is at least as important because it is an integral part of the whole cooling picture.

 

 Just food for thought.

 Good luck.  

  

    

   

  



 

         

  

One site keeps you connected to all your email: AOL Mail, Gmail, and Yahoo Mail. Try it now.  

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Afterfxllc(at)aol.com
Guest

Posted: Sat Dec 20, 2008 6:44 am Post subject: Engine Cooling

Roger,

  

 You are right to a point but there is no better teacher than experience. I  didn't want to sound harsh with my comment to Brady but after reading it again  it was just that. I am working on ram air ducts for the 601 and 650 to fit our  new cowling and while it looks like it should work in theory will it work in the  air? 

  

    

                                                       

  



  



  	  Quote: 	
		     

Jeff;   

    

It is always better    to have built â€œone airplaneâ€ before advising folks on their airplane problems,    or for that matter, 10 airplanes. But skills in cutting metal and driving    rivets has little to do with intellectual skills such as analyzing studies and    applying knowledge to abstract problems such as thermal conduction (thatâ€™s    what engineers do).   

Take it easy on    Brady, he is on the right track and just trying to help (no good deed goes    unpunished !!!!)   

    

Roger 	


 

  



One site keeps you connected to all your email: AOL Mail, Gmail, and Yahoo Mail. Try it now.

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Dec 20, 2008 11:44 am Post subject: Engine Cooling

If the heated air can't get out of the cowling, it doesn't matter how  

well designed the inlets and baffling are. In the ideal cooling  

design, the outlet area should be about 1 1/2 times the inlet area. In  

any case, the outlet must be at a lower pressure than the inlet.  

Putting a lip projecting down into the airstream ahead of the outlet  

will often greatly improve the effectiveness of the cooling. The  

turbulence caused by the lip creates a low pressure area at the outlet  

that improves airflow.



On Dec 20, 2008, at 9:42 AM, Afterfxllc(at)aol.com wrote:



 	  Quote: 	
		   Roger,



 You are right to a point but there is no better teacher than  

 experience. I didn't want to sound harsh with my comment to Brady  

 but after reading it again it was just that. I am working on ram air  

 ducts for the 601 and 650 to fit our new cowling and while it looks  

 like it should work in theory will it work in the air?


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

BobbyPaulk(at)comcast.net
Guest

Posted: Sun Dec 21, 2008 3:17 pm Post subject: Engine Cooling

all,

many thanks to Jeff for the photos and logic to help solve the high temps on the rear cylinders. also to Randy who has the same problem. i had tried adding an 1 1/2" skirt to the bottom of the cowl to no avail. i have also tried large deflectors in the ram air ducts. i also trimmed them 1/8" at a time until i wound up with small deflectors. the oil cooler is sealed tightly as is the ram air ducts to the cowl openings.  i will keep experimenting to find the right combination. 

thanks to all who offered help. i will post the findings when you or i solve the problem. 



thanks again



bobby

70.8 hrs. 

601 XL Jab. 3300

planes_by_ken(at)bellsout
Guest

Posted: Tue Dec 30, 2008 10:33 am Post subject: Engine Cooling

Better than ram air is a defuser.  If you look at modern versions of older designs the cooling air inlet area is now about 30% of what they were.  The air path forms a divergent duct.  By Bernoulli's principle the air slows down and pressure goes up.  Manufactures look for a pressure drop  from top to the bottom  of the engine.  One plane I have worked on  needed  a 6"  of water pressure difference.  Some aircraft use an augmenter exhaust to lower the pressure in the lower cowl.  This uses the exhaust flow to create a venturi effect.  The images are of a Diamond DA-40 with a 180HP Lycoming.  The air inlets are about 6" in diameter.  They feed into a plenum defuser.  Air must be prevented from getting past the baffle seals.  Also air will try to leak around the propshaft.

 Teaching turbine engines at the moment,

 Ken Lilja

 [img]cid:part1.00060403.04080208(at)bellsouth.net[/img][img]cid:part2.06040207.02050603(at)bellsouth.net[/img][img]cid:part3.05010801.04090100(at)bellsouth.net[/img][img]cid:part4.02090707.09060908(at)bellsouth.net[/img]

 

 

 

 

 

 Afterfxllc(at)aol.com (Afterfxllc(at)aol.com) wrote:  	  Quote: 	
		                 Brady

    

   With all due respect, how many aircraft have you built? You are starting to be the WW of the Zenith list. I think you are a smart guy and like what you are trying to do but wouldn't it be better to have built at least 1 airplane before you hand out answers to others problems? Having worked on a Jab that overheats it is a pain in the ass engine when it comes to cooling. Jab will tell you they don't have a problem but I have seen too many posts about overheating to believe that. 

    

   BTW if the intake is small where is it going to "Suck" the air from? The Jab uses small deflectors inside the baffles and if they are too big or small the rear cylinder will overheat.

    

   Jeff

    

    

    

    

   Bobby,

   

 Be sure not to over look the exit.

 All the intake in the world won't do you any good if it has nowhere to go.

 Try to "suck" the cooling through.

   

 I have seen studies that say the intake is far less important than the exhaust side of the cooling system.

   

 Also be sure you oil cooler is getting fresh air.

 the oil cooler is at least as important because it is an integral part of the whole cooling picture.

   

 Just food for thought.

 Good luck.

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ideaz1(at)sbcglobal.net
Guest

Posted: Thu Jan 01, 2009 10:48 am Post subject: Engine Cooling

Would you please explain what a defuser consists of  and what you mean by a divergent duct. I am interested in learning more on this  topic.

 If you would rather email me direct to avoid having  your body parts chewed off by those on the list who insist on being righter than  anyone else, please do.

  

 Thanks, 

 Dirk Zahtilla ideaz1(at)sbcglobal.net (ideaz1(at)sbcglobal.net) 

 Interem Airport Manager, CXP

 Carson City, Nv.

   [quote][b]

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Jan 01, 2009 11:28 am Post subject: Engine Cooling

A definition From the web: "A diffuser is a passage so shaped (usually  

in the form of a divergent duct) that it will change the  

characteristics of a fluid flow from a certain pressure and velocity  

at the inlet to a lower velocity and higher pressure at the outlet.  

Generally, the diffusion must be carried out in a well-streamlined  

passage having smooth interior surfaces, and sides not diverging at so  

great an angle as to cause the fluid to leave the sides of the  

diffuser. By reducing the velocity through increasing the cross- 

sectional area of flow, the pressure may be built up as the velocity  

head is diminished. Diffusers are used to conserve energy by  

efficiently converting velocity head into pressure."



A divergent duct is simply a duct whose cross sectional area increases  

in the down stream direction. Because slower moving air remains in  

contact with the cooling fins for a longer period of time, it can soak  

up more heat from the engine to carry away. You still have to make  

sure the cooling exit duct is larger than the inlet duct and is  

located in a area of lower pressure.

On Jan 1, 2009, at 1:45 PM, Dirk Zahtilla wrote:



 	  Quote: 	
		   Would you please explain what a defuser consists of and what you  

 mean by a divergent duct. I am interested in learning more on this  

 topic.

 If you would rather email me direct to avoid having your body parts  

 chewed off by those on the list who insist on being righter than  

 anyone else, please do.


	




-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

psm(at)att.net
Guest

Posted: Thu Jan 01, 2009 11:48 am Post subject: Engine Cooling

Hi Dirk,



 There is a really great magazine article describing this new technology.  Title: Cooling Drag.  Page 106. EAA Sport Aviation.  December 2007.  Author Christopher Zavatson.



 I strongly recommend this article.  I have read it a few times and keep it handy for reference.



 Good luck,



 Paul

 XL getting close



 

 At 10:45 AM 1/1/2009, you wrote:

 [quote]Would you please explain what a defuser consists of and what you mean by a divergent duct. I am interested in learning more on this topic.

 If you would rather email me direct to avoid having your body parts chewed off by those on the list who insist on being righter than anyone else, please do.

  

 Thanks, 

 Dirk Zahtilla ideaz1(at)sbcglobal.net (ideaz1(at)sbcglobal.net) 

 Interem Airport Manager, CXP

 Carson City, Nv.

 

  	  Quote: 	
		  

[/b] 	
[b]

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