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Continuation on High CHT problem
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n616tb(at)btsapps.com
Guest

Posted: Sun Dec 10, 2006 9:31 am Post subject: Continuation on High CHT problem

I reported on these earlier and received lots of great info and solutions.  After plugging every possible hole I could find in my baffling here are the results.  Yesterday was quite cool here in East  Texas and a flight was in order.  After take off I climbed over the lake at the end of the runway and noticed the CHT on # 3 was over 400.  By the time I reached 2500’ AGL the temp was at 446 degrees so I leveled off and allowed it to settle out.  After a few minutes the temps came down to about 406 but was about the same on 2, 3, and 4.  I landed and removed the top cowl so I could block off the oil cooler by about ½ of the distance exposed.  After another short flight the temps did not go above 412 on climb and then about 402 on cruise.  The big difference was now cylinder #4 is the hottest.  The oil temp climbed from around 154 to 182 so this was positive for this time of year.  My oil cooler is mounted to the back baffle on the left side of the engine.  

   

I am at a bit of a loss for why the temps will not come down.  One of the solutions offered was to add louvers to my lower cowl to increase exit air area.  I am willing to do this but have some reservations.  Increasing exit air would increase air flow through the cowl but should increase drag and therefore performance.  How significant would this be?  Obviously I would be willing to give up a little performance if I can keep it cool.  Also it seems odd that hundreds, maybe thousands of RV’s are flying and staying cool enough without louvers and so I wonder what else I may be leaving unchecked.  I am convinced I have no leaks at this point.  Here is what I have done:  

   

Closed up all leaks in baffling especially around the front and around the upper ramps.  

Added a deflector in front of cylinder # 1  

RTV around every crack or seam where air could exit  

Plugged a big hole between the case and #3 in front of dipstick housing  

Blocked the heater exit on the right side of plane as it was pulling air from #3 ( I have two heater muffs.)  

   

My baffle is very tight and I see no areas where there could be a leak.  I do notice the area above the cylinder on the right side is much less since the cylinder is further forward and under the upper ramp.  Maybe this could be modified to raise the upper ramp some and equal this out.  

   

Because my temps change accordingly when I takeoff, cruise, and land I think the probes are at least responding.  I also think since blocking the oil cooler caused a change and now #4 is hottest indicates they must be working.  There is no setting on these that I am aware of, but maybe I should have the system checked out by Vision Microsystems to verify they are reading correctly.  

   

Thanks for any help  

Tim  

        [quote][b]

kboatright1(at)comcast.ne
Guest

Posted: Sun Dec 10, 2006 10:07 am Post subject: Continuation on High CHT problem

Tim,

  

 What speeds are you using for climb  out?

  

 How many hours on your engine?

  

 Which engine do you have, and which airframe?   

  

 Apologies if you've posted all of this information  previously.

  

 KB

 [quote]   ---

ronlee(at)pcisys.net
Guest

Posted: Sun Dec 10, 2006 10:08 am Post subject: Continuation on High CHT problem

 	  Quote: 	
		  If you have verified the probe monitor for accuracy I would do that. 	


 I had high oil temps and CHT and opening the cowl and adding 

 louvers dropped them a lot.  I doubt that any speed reduction

 is measurable.



 Obviously check in to other factors (mag timing etc).



 Ron Lee



     [quote][b]

ronlee(at)pcisys.net
Guest

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

 	  Quote: 	
		  

 Blocked the heater exit on the right side of plane as it was pulling air from #3 ( I have two heater muffs.)

 	


 I also had two heater muffs with the flow blocking scat tubes.



 That was my first change (remove the extra heater muff and tubes) and that 

 helped as well.



 Ron Lee



 

     [quote][b]

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Sun Dec 10, 2006 10:27 am Post subject: Continuation on High CHT problem

In a message dated 12/10/2006 11:33:56 AM Central Standard Time, n616tb(at)btsapps.com writes:

  	  Quote: 	
		  I should have the system checked out by Vision Microsystems to verify they are reading correctly. 	


 >>>

  

 I don't recall if you mentioned it earlier, but have you checked the probes in boiling water to see if they read around 212F?  Pretty sure you could heat some oil hotter and dip the tips of the probes into it (verify with cooking/candy thermometer).  I've never tried this, but sound reasonable?

  

 Might also try blocking one or both of the heat muffs- these are normally huge short-circuits around your baffles if they flow all the time- far more than all those little leaks you plugged up.

  

 Mark

  [quote][b]

_________________
From The PossumWorks...

n616tb(at)btsapps.com
Guest

Posted: Sun Dec 10, 2006 11:25 am Post subject: Continuation on High CHT problem

Hi Kyle,  

   

I use 110 Mph on climb out  

I have 24 hours on my RV-6  

O-360 A1A with Hartzell constant speed  

   

No problem  

Tim  

           

  

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Kyle Boatright

 Sent: Sunday, December 10, 2006 12:06 PM

 To: rv-list(at)matronics.com

 Subject: Re: Continuation on High CHT problem  

  

     

Tim,  

    

   

    

What speeds are you using for climb out?  

    

   

    

How many hours on your engine?  

    

   

    

Which engine do you have, and which airframe?    

    

   

    

Apologies if you've posted all of this information previously.  

    

   

    

KB  

  [quote]    

---

n616tb(at)btsapps.com
Guest

Posted: Sun Dec 10, 2006 11:25 am Post subject: Continuation on High CHT problem

I was thinking about the timing issue.  It runs great, but I have not checked it.  Honestly it has been so long since I have done this I am not sure I remember how.  I may need to find someone to give me a refresher and check it.  

   

Tim  

           

  

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Ron Lee

 Sent: Sunday, December 10, 2006 12:08 PM

 To: rv-list(at)matronics.com

 Subject: Re: Continuation on High CHT problem  

  

    	  Quote: 	
		    

If you have verified the probe monitor for accuracy I would do that.  	
  



 I had high oil temps and CHT and opening the cowl and adding 

 louvers dropped them a lot.  I doubt that any speed reduction

 is measurable.

 

 Obviously check in to other factors (mag timing etc).

 

 Ron Lee   	  Quote: 	
		    www.aeroelectric.com 	
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        [quote][b]

n616tb(at)btsapps.com
Guest

Posted: Sun Dec 10, 2006 11:27 am Post subject: Continuation on High CHT problem

My heater outlets are a series of holes about 3/8 inch.  I have maybe 5 or 6 of them in the baffle, plus the heat muff has smaller holes to slow the air down.  I blocked the outlet on the right side behind #3 with tape and it made no difference.  I could block the other one for a test.  

   

Tim  

           

  

From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Ron Lee

 Sent: Sunday, December 10, 2006 12:11 PM

 To: rv-list(at)matronics.com

 Subject: Re: Continuation on High CHT problem  

  

    	  Quote: 	
		    



 Blocked the heater exit on the right side of plane as it was pulling air from #3 ( I have two heater muffs.)  	
  



 I also had two heater muffs with the flow blocking scat tubes.

 

 That was my first change (remove the extra heater muff and tubes) and that 

 helped as well.

 

 Ron Lee

 

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n616tb(at)btsapps.com
Guest

Posted: Sun Dec 10, 2006 11:30 am Post subject: Continuation on High CHT problem

No, I haven’t but suppose it would be viable.  Do the probes respond the same in water as they would in just the air?  This would be a valid test I think.  I did block one heat muff robbing air outlet with no change.  

Thanks  

Tim  

           

  

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

 Sent: Sunday, December 10, 2006 12:26 PM

 To: rv-list(at)matronics.com

 Subject: Re: Continuation on High CHT problem  

  

       

In a message dated 12/10/2006 11:33:56 AM Central Standard Time, n616tb(at)btsapps.com writes:  

   	  Quote: 	
		    

I should have the system checked out by Vision Microsystems to verify they are reading correctly.  	
  

    

 	  Quote: 	
		  >>   

    
	


   

    

I don't recall if you mentioned it earlier, but have you checked the probes in boiling water to see if they read around 212F?  Pretty sure you could heat some oil hotter and dip the tips of the probes into it (verify with cooking/candy thermometer).  I've never tried this, but sound reasonable?  

    

   

    

Might also try blocking one or both of the heat muffs- these are normally huge short-circuits around your baffles if they flow all the time- far more than all those little leaks you plugged up.  

    

   

    

Mark  

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ronlee(at)pcisys.net
Guest

Posted: Sun Dec 10, 2006 12:23 pm Post subject: Continuation on High CHT problem

At 12:27 PM 12/10/2006, you wrote:

  	  Quote: 	
		  My heater outlets are a series of holes about 3/8 inch.  I have maybe 5 or 6 of them in the baffle, plus the heat muff has smaller holes to slow the air down.  I blocked the outlet on the right side behind #3 with tape and it made no difference.  I could block the other one for a test. 	


 Did you remove the tubing.  That impedes the efficient flow of air.



 Another point is that your engine may not be broken in yet.



 Ron Lee    [quote][b]

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Sun Dec 10, 2006 12:36 pm Post subject: Continuation on High CHT problem

In a message dated 12/10/2006 1:31:58 PM Central Standard Time, n616tb(at)btsapps.com writes:

  	  Quote: 	
		  Do the probes respond the same in water as they would in just the air? 	


 I would think that besides the heat transferring more quickly from the liquid to the probe than from air, the probe would never know.  Besides, having the probe and themometer in a common container of liquid fairly well ensures they are at the same approximate temp.

  

 I would suggest caution how deep into the liquid you immerse the probe since I'm not familiar with how they are sealed- just part of the metal barrel on the end of the probe in the liquid should suffice.  Possibly heat a very small pan of peanut/canola/corn/whatever oil ("you put my good candy themometer in USED MOTOR OIL?!?!?!") and heat until 400-425 degrees or so as indicated by the themometer.  A meat thermometer would probably work as well.  Take it over to engine where you already have the probe dangling and just dip the first half-inch or so into the oil.  I'd think you'd have it warmed up to oil temp in 20-30 seconds, but again, I've never tried this- someone else out there could probably offer more specific advice.

  

 Mark

  [quote][b]

_________________
From The PossumWorks...

walter(at)tondu.com
Guest

Posted: Sun Dec 10, 2006 1:23 pm Post subject: Continuation on High CHT problem

Have you seen this post I made in June regarding the solution to

my High CHT problems.  Check out the poll results...



http://www.vansairforce.com/community/showthread.php?t=8209

-- 

Walter Tondu

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

http://www.evorocket.com - Building

khorton01(at)rogers.com
Guest

Posted: Sun Dec 10, 2006 5:29 pm Post subject: Continuation on High CHT problem

This is a viable test.



I tested my CHT probes by sticking them in a can of water and heating  

it to a boil with a propane torch.  They all read within one degree C  

of the boiling point of water.  If you altitude is much different  

from sea level, or the atmospheric pressure is much different from  

standard, you may want to allow for the small decrease in water's  

boiling with altitude.  This info is available on the web in multiple  

places.



Kevin Horton



On 10 Dec 2006, at 14:29, Tim Bryan wrote:



 	  Quote: 	
		   No, I haven’t but suppose it would be viable.  Do the probes  

 respond the same in water as they would in just the air?  This  

 would be a valid test I think.  I did block one heat muff robbing  

 air outlet with no change.



 Thanks



 Tim



 From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list- 

 server(at)matronics.com] On Behalf Of Fiveonepw(at)aol.com

 Sent: Sunday, December 10, 2006 12:26 PM

 To: rv-list(at)matronics.com

 Subject: Re: Continuation on High CHT problem



 In a message dated 12/10/2006 11:33:56 AM Central Standard Time,  

 n616tb(at)btsapps.com writes:



 I should have the system checked out by Vision Microsystems to  

 verify they are reading correctly.



 >>>



 I don't recall if you mentioned it earlier, but have you checked  

 the probes in boiling water to see if they read around 212F?   

 Pretty sure you could heat some oil hotter and dip the tips of the  

 probes into it (verify with cooking/candy thermometer).  I've never  

 tried this, but sound reasonable?



 Might also try blocking one or both of the heat muffs- these are  

 normally huge short-circuits around your baffles if they flow all  

 the time- far more than all those little leaks you plugged up.

martin(at)gbonline.com
Guest

Posted: Sun Dec 10, 2006 6:37 pm Post subject: Continuation on High CHT problem

Tim,

 7 years ago when I finished my RV8, I experienced a  similar problem.  After double checking all baffling etc. to no avail, I  retarded the ignition  a couple of degrees and that ended the  problem.  Double check the specifications and your timing equipment to make  sure that it is accurate.  Good luck.

 

DICK Martin

 RV8 N233M

 the fast one

 [quote]   ---

john(at)fureychrysler.com
Guest

Posted: Mon Dec 11, 2006 6:02 am Post subject: Continuation on High CHT problem

I had  similar problems on my O-320 RV6A even though I had a very tight plenum. In  desperation I removed the plenum which did no good. A week later I read an  article in one of the main aviation magazines about casting flash and roughness  in the cylinder fins and around the spark plug. About an hours work with a small  rat tail file in the dremmel and my problems were gone. There have been several  posts about this in the past two years. Not sure how to find the article but I  can give you all the details off line if needed.

  

 John  Furey

 john(at)fureychrysler.com (john(at)fureychrysler.com)

 330-495-5189

   [quote][b]

aerobubba(at)earthlink.ne
Guest

Posted: Mon Dec 11, 2006 7:29 am Post subject: Continuation on High CHT problem

Hi Tim-



 	  Quote: 	
		  I reported on these earlier and received lots of great info and 

solutions.


	


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

opportunity to fly yet, so I've not tinkered with this yet, but IIRC you

need a bit of a gap between the fins and the baffles.

glen matejcek

aerobubba(at)earthlink.net

Hopperdhh(at)aol.com
Guest

Posted: Mon Dec 11, 2006 8:03 am Post subject: Continuation on High CHT problem

In a message dated 12/11/2006 10:32:18 AM Eastern Standard Time, aerobubba(at)earthlink.net writes:

  	  Quote: 	
		  --> RV-List message posted by: "glen matejcek" <aerobubba(at)earthlink.net>



Hi Tim-



 	  Quote: 	
		  I reported on these earlier and received lots of great info and 

solutions.


	


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

opportunity to fly yet, so I've not tinkered with this yet, but IIRC you

need a bit of a gap between the fins and the baffles.

glen matejcek

aerobubba(at)earthlink.net 	


 I don't think this is correct, Glen.

  

 Dan Hopper

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

  [quote][b]

Hopperdhh(at)aol.com
Guest

Posted: Mon Dec 11, 2006 8:15 am Post subject: Continuation on High CHT problem

Tim,

  

 You do, of course, need adequate space for the cooling air to escape at the bottom of each cylinder.  I think I have about 2 or 2  1/2 inches.  Also, you should have an inter-cylinder baffle between each pair of cylinders.  You do have these, don't you?

  

 Dan Hopper

 RV-7A

  

 In a message dated 12/11/2006 11:07:37 AM Eastern Standard Time, Hopperdhh(at)aol.com writes:

  	  Quote: 	
		    In a message dated 12/11/2006 10:32:18 AM Eastern Standard Time, aerobubba(at)earthlink.net writes:

  	  Quote: 	
		  --> RV-List message posted by: "glen matejcek" <aerobubba(at)earthlink.net>



Hi Tim-



 	  Quote: 	
		  I reported on these earlier and received lots of great info and 

solutions.


	


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

opportunity to fly yet, so I've not tinkered with this yet, but IIRC you

need a bit of a gap between the fins and the baffles.

glen matejcek

aerobubba(at)earthlink.net 	


 I don't think this is correct, Glen.

  

 Dan Hopper

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

 	  Quote: 	
		  



p://www.aeroelectric.com/">http://www.aeroelectric.com/

 href="http://www.buildersbooks.com/">http://www.buildersbooks.com/

ttp://www.kitlog.com/">http://www.kitlog.com/

ttp://www.homebuilthelp.com/">http://www.homebuilthelp.com/

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

="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List



	
	


 

  [quote][b]

billsettle(at)bellsouth.n
Guest

Posted: Mon Dec 11, 2006 9:03 am Post subject: Continuation on High CHT problem

John,



What brand of cylinders do you have, and did the article mention whether or not one brand was more problematic than another?



Bill

-8 Wings

 	  Quote: 	
		   

 From: "John Furey" <john(at)fureychrysler.com>

 Date: 2006/12/11 Mon AM 09:01:38 EST

 To: <rv-list(at)matronics.com>

 Subject: RE: Continuation on High CHT problem

 

 I had similar problems on my O-320 RV6A even though I had a very tight

 plenum. In desperation I removed the plenum which did no good. A week later

 I read an article in one of the main aviation magazines about casting flash

 and roughness in the cylinder fins and around the spark plug. About an hours

 work with a small rat tail file in the dremmel and my problems were gone.

 There have been several posts about this in the past two years. Not sure how

 to find the article but I can give you all the details off line if needed.

 

 John Furey

 john(at)fureychrysler.com

 330-495-5189

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Mon Dec 11, 2006 9:17 am Post subject: Continuation on High CHT problem

Maybe this is about insuring a small gap between the rear baffle and cylinder number 4. I recall that an 1/8” gap is required, which can be achieved by making a washer or spacer out of aluminum stock.  

   

Terry  

   

         

  

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

 Sent: Monday, December 11, 2006 8:02 AM

 To: rv-list(at)matronics.com

 Subject: Re: RE: Continuation on High CHT problem  

  

       

In a message dated 12/11/2006 10:32:18 AM Eastern Standard Time, aerobubba(at)earthlink.net writes:  

   	  Quote: 	
		    

--> RV-List message posted by: "glen matejcek" <aerobubba(at)earthlink.net>

 

 Hi Tim-

 

 >I reported on these earlier and received lots of great info and 

 >solutions.

 

 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

 opportunity to fly yet, so I've not tinkered with this yet, but IIRC you

 need a bit of a gap between the fins and the baffles.

 

 

 glen matejcek

 aerobubba(at)earthlink.net  	
  

    

I don't think this is correct, Glen.  

    

   

    

Dan Hopper  

    

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

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