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Continuation on High CHT problem
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rv8a2001(at)yahoo.com
Guest

Posted: Mon Dec 11, 2006 9:20 am Post subject: Continuation on High CHT problem

I must agree this does not sound right. My head temps were going up slowly over a period of time and I though I had better take a looksee. What I found was loose cylinder baffles the ones that wrap around the cylinder. I tightened them up and my temps went back to normal.

 

Scott Bilinski

RV-8a

 



 ---

HCRV6(at)comcast.net
Guest

Posted: Mon Dec 11, 2006 10:17 am Post subject: Continuation on High CHT problem

bicyclop(at)pacbell.net
Guest

Posted: Mon Dec 11, 2006 11:18 pm Post subject: Continuation on High CHT problem

Yah, except that it’s # 3. On the parallel valve Lycs, the fins are really shallow on one side to let it sit right next to another cylinder and the shallow side is to the rear on the right side of the airplane. When I provided a little more gap back there, # 3 cooled off about 30 or 40 degrees on our O-320.  

   

Pax,  

   

Ed Holyoke  

   

--

martin(at)gbonline.com
Guest

Posted: Thu Dec 21, 2006 6:19 pm Post subject: Continuation on High CHT problem

Glen,

 I also do not think that this is correct.

 I have 1400 hrs on my RV8. No gap, no cooling problem

 I have always been taught that loose and poorly fit baffles were the  primary cause of cooling problems.

 Dick Martin

 RV8 N233M

 the fast one

 [quote]   ---

martin(at)gbonline.com
Guest

Posted: Thu Dec 21, 2006 6:28 pm Post subject: Continuation on High CHT problem

Tim,

 to add to Dan's comments, on the IO390s most of the air racers are using a  spacing on the baffles that wrap around the botton side of the cylinder of 2  1/4" on the cylinder head portion and 1" on the cylinder barrel portion.   Some engine installations will require minor tweaking of adding or subtracting a  quarter inch to these demensions.  Good luck.

 Dick Martin

 RV8 N233M

 the fast one

 [quote]   ---

walter(at)tondu.com
Guest

Posted: Thu Dec 21, 2006 6:49 pm Post subject: Continuation on High CHT problem

On 12/21  8:07, dick martin wrote:



 >        I haven't noticed anyone referencing ensuring that you have adequate

 >        clearance between the baffles and the edges of the fins.  I've not had

 >        the



Are you perhaps mentioning the gap between the #3 cylinder and the 

rear baffle?  If so, I did see a decent drop (30F) when I placed a

1/8th gap there.



-- 

Walter Tondu

http://www.rv7-a.com - Flying!

http://www.evorocket.com - Building

rocketbob(at)gmail.com
Guest

Posted: Thu Dec 21, 2006 7:06 pm Post subject: Continuation on High CHT problem

It is correct, I know of at least a half dozen RV's or Rockets belonging to friends that have spaced the baffle away from the #3 cylinders with washers (#5 on the 540).  It will drop the CHT's on those cylinders by 30 degrees, if for some reason those cylinders are running hot.  It also works on the #1 cylinder as well.  The theory is it allows more cooling air to flow around the hottest side of the cylinder which is the exhaust valve side.. 



Regards,

Bob Japundza

RV-6 flying F1 under const.



On 12/21/06, dick martin <martin(at)gbonline.com (martin(at)gbonline.com) > wrote:[quote]       Glen,

 I also do not think that this is correct.

 I have 1400 hrs on my RV8. No gap, no cooling problem

 I have always been taught that loose and poorly fit baffles were the  primary cause of cooling problems.

 Dick Martin

 RV8 N233M

 the fast one

 [quote]   ---

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Fri Dec 22, 2006 3:28 am Post subject: Continuation on High CHT problem

That is correct. A little gap on # 3 and also # 1 has a great 

effect. It is not magic. It is the fact the part of the cylinder 

that is up against the baffle has very shallow fins. The cylinders 

are NOT symetric but are all identical. The side fins are deeper 

on the exhaust valve side. The intake side the fins are shallow. 

So the #3 cylinder has it's shallow fins against the baffle. If 

the baffle starts high and is too tight you get no air flow down 

and under the cylinder. The air gets choked off on the shallow 

side and keeps it from getting to the lower part of the cylinder 

where the fins get deeper again. It has a significant effect.

  

Mr. Dick Martin

  and gang there are many reasons that some engine 

run hot. Dick you have a totally different set up with a 

plenum don't you? I know the lower baffles are the same 

or similar but people do have cooling problems. Each 

RV is different. It can [quote][b]

aerobubba(at)earthlink.ne
Guest

Posted: Fri Dec 22, 2006 6:17 am Post subject: Continuation on High CHT problem

Howdy D & D-



Interesting observations.  As I'm tinkering with cooling considerations and

details, I'd love to run this to ground.  A lot of info has been posted

piecemeal, and I'd like to bring it all together in one place and clarify

some stuff for posterity as well as my own edification.  As I understand it:



First, I absolutely agree that leaky baffles are very significant and the

elimination of leaks is of prime importance.  



Looking closely at my 200 hp angle valve IO-360, the casting part line on

the fwd side of #2 cyl and the aft side of #3 cyl in the region from the

inbd edge of the intake port to the outbd end of the head is tangent to /

flush with the edge of the cooling fins.  From the inbd edge of the port to

the base of the head, the min depth of the fins is about 1/8 inch. 

Therefore, baffles that were truly tight in this region would cause zero

airflow around the back side of the #3 head and the lower front quadrant of

#2 at their extremities, and little airflow through the next region inbd.



My baffle kit from Van's fits such that there is a gap on the order of 1/8

inch between #3 cyl and the rear baffle.  The way my particular baffle

parts came, this gap is not really adjustable and isn't a product of

installation error.  



There is about 3/32 gap between the heads in the inter cylinder area.



I have no idea if Van's baffle kits have changed over time, and if perhaps

some folks with the angle valve engines have older baffle kits that might

not have the clearance gap built in.



When convenient, could either / both of you guys verify that there is in

fact no gap between your rear baffles and #3 at the casting part line?  I'm

not throwing rocks, casting aspersions, or anything else negative, but I am

truly intrigued by your comments in light of other's experiences as well as

the config of my baffle kit.



TIA-



glen matejcek

aerobubba(at)earthlink.net



 	  Quote: 	
		   Glen,

 I also do not think that this is correct.

 I have 1400 hrs on my RV8. No gap, no cooling problem

 I have always been taught that loose and poorly fit baffles were the 

 primary cause of cooling problems.


	




 	  Quote: 	
		     I don't think this is correct, Glen.



   Dan Hopper

   RV-7A 200 HP Angle Valve IO-360, No gap and no cooling problem.

martin(at)gbonline.com
Guest

Posted: Fri Dec 22, 2006 7:23 pm Post subject: Continuation on High CHT problem

Glen,

All baffles are tight.   Some other thoughts!

The IO 360 is a partially oil cooled engine.  What size is your oil cooler? 

What Brand? How is it installed ?  Are your oil temps cool or hot  ( ideal 

is 190 - 210 degrees f )



Dick Martin

RV8 N233M

IO-390  (first engine was IO-360  10/1  operated 900 hr

the fast one



---

Hopperdhh(at)aol.com
Guest

Posted: Sat Dec 23, 2006 5:45 am Post subject: Continuation on High CHT problem

Glen,

  

 I used the baffle kit from Vans.  I haven't cut down the front deflectors.  I will let you know about the gaps as soon as I have the top cowl off again -- in the next few days.

  

 I have a big SW oil cooler fed with a 4 inch SCAT tube on the right side of the firewall.  Active area is 5.5 by 5.5 inches.  I made up an aluminum shroud which is about half good as far as the airflow goes.  The cooler is mounted at about 40 degrees from vertical.  My oil temp very seldom goes above the vernatherm temp of about 190 degrees.  Most I see is about 230 on climbout on a really hot day.  I could force it higher by climbing slower, longer though.  I'd say I have about the right amount of oil cooling.  I went to the SW cooler after using a Niagara at first.  The SW helped -- maybe 10 or 15 degrees.

  

 One weird thing is that my number 4 CHT runs about 20 degrees cooler than the other 3.  Typical temps are around 350 degrees F. with number 4 being 320.  The other 3 are usually within a 15 degree window, but no. 4 is always noticeably cooler.  This almost has to be the baffling.  It has been the same with 2 different engines, although I used the same fuel injection and mags on both.  I tested the CHT probes by clamping no. 2 and no. 4 together in a piece of copper tubing, and heating it with my hot air gun.  They tracked together within about 1 degree F.

  

 Dan Hopper

 RV-7A

 IO-360-A1A

  

  

 In a message dated 12/22/2006 10:25:17 PM Eastern Standard Time, martin(at)gbonline.com writes:

 [quote]--> RV-List message posted by: "dick martin" <martin(at)gbonline.com>



Glen,

All baffles are tight.   Some other thoughts!

The IO 360 is a partially oil cooled engine.  What size is your oil cooler? 

What Brand? How is it installed ?  Are your oil temps cool or hot  ( ideal 

is 190 - 210 degrees f )



Dick Martin

RV8 N233M

IO-390  (first engine was IO-360  10/1  operated 900 hr

the fast one



---

Hopperdhh(at)aol.com
Guest

Posted: Sat Dec 23, 2006 5:51 am Post subject: Continuation on High CHT problem

In a message dated 12/23/2006 8:48:24 AM Eastern Standard Time, Hopperdhh(at)aol.com writes:

  	  Quote: 	
		   One weird thing is that my number 4 CHT runs about 20 degrees cooler than the other 3.  Typical temps are around 350 degrees F. with number 4 being 320.  The other 3 are usually within a 15 degree window, but no. 4 is always noticeably cooler.  This almost has to be the baffling.  It has been the same with 2 different engines, although I used the same fuel injection and mags on both.  I tested the CHT probes by clamping no. 2 and no. 4 together in a piece of copper tubing, and heating it with my hot air gun.  They tracked together within about 1 degree F.

  

 Dan Hopper

 RV-7A

 IO-360-A1A

	


 Oops!  My math is not too good.  I should say 20 or 30 degrees cooler on number 4.

  

 Dan

  

  [quote][b]

aerobubba(at)earthlink.ne
Guest

Posted: Sun Dec 24, 2006 5:24 am Post subject: Continuation on High CHT problem

Hi Dan-



Thanks for all the info.  It's going to be very interesting seeing how this

plays out.  It looks like your cooler is about 20% larger than mine, and is

mounted similarly.  I spent a lot of time trying to come up with a good

diffuser for the cooler-  time will tell if it is a pipe dream.  Your CHT

split is interesting.  I'll be very curious to see if I have a similar

situation, since I'm picking the cooler flow off the opposite side, also.



Hi Dick-



My cooler is the recommended 4 3/8 by 5 3/4 (post debacle) Positech.  It is

suspended from the engine mount, aircraft right, in a nearly horizontal

position.  It is fed by a moderately sexy diffuser that will be fed by a 4"

scat off the plenum.  I hope to fly it this spring.  After all, it's only

been 9 years, 5 jobs, 2 stretches of unemployment, and one degree since I

started this project...  I forget:  Is that part of the glamour or of the

glory of aviation?  I get so cornfused!  ; - ) 



glen matejcek

aerobubba(at)earthlink.net

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