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High CHTs Epilogue

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mark.t.mueller(at)comcast
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Posted: Sat Apr 21, 2012 5:31 pm Post subject: High CHTs Epilogue

A few weeks ago I asked for advice/comments on high CHTs after my annual inspection.  I appreciate the responses I got back, and most concentrated on baffling and timing.



My IA swore the timing on the engine was correct, and the cabin heating duct in front of the exit ramp would not effect cooling flow much.  Spent a day trying to troubleshoot, and he became convinced it was an instrumentation issue.  Kind of made sense, but I was skeptical.  He did find one of the CHT probes had significant tip wear (they were well over 10 years old...)

 



After new probe installation, the monitor indicated a 10 degree drop in CHTs, but still running well over 430 in cruise...

Last weekend, I re-routed the heater duct away and around the exit ramps.  A pain, but just took some time and extra materials.  Noticed an immediate improvement in cooling, but CHTs were still too high for my liking.

 



I ordered a Mag-Rite timing tool kit from ATS.  Digital protractor and nylon cylinder probe to enable very precise location of actual TDC (as opposed to a mark on a ring and location on case.)  Can't say enough good things about this kit (worth every penny), very easy to use, and the digital protractor has 1/10 degree resolution.  Re-timed my mags (I have a LASAR ignition) to specs.  To say the timing was 'off' is an understatement.  It was WAY off.  The smoothness of the LASAR masked the issue well, and the motor put out good power.

 



Now that it is 'dialed in' to within a tenth of a degree of accuracy, the CHTs dropped over 20F.

So, I improved cooling air flow, and fixed my timing.  This is AFTER paying an IA for a complete annual, and coming back for troubleshooting.

 



At the end of the day, the lesson I learned is after over 10 years of ownership, I will know when 33R is "dialed in" or not regardless of what an IA may believe even if he has been taking care of this aircraft for several years... Mark

 

  [quote][b]

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teamgrumman(at)yahoo.com
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Posted: Sat Apr 21, 2012 8:52 pm Post subject: High CHTs Epilogue

Mark,

That's good to hear. When my plane is "dialed in" it will still run 410 straight and level at 4000 feet. Can't wait to get the IO360 on and finished. 



Gary

Sent from my iPad



On Apr 21, 2012, at 6:30 PM, "Mark T. Mueller" <mark.t.mueller(at)comcast.net (mark.t.mueller(at)comcast.net)> wrote:



[quote]A few weeks ago I asked for advice/comments on high CHTs after my annual inspection.  I appreciate the responses I got back, and most concentrated on baffling and timing.



My IA swore the timing on the engine was correct, and the cabin heating duct in front of the exit ramp would not effect cooling flow much.  Spent a day trying to troubleshoot, and he became convinced it was an instrumentation issue.  Kind of made sense, but I was skeptical.  He did find one of the CHT probes had significant tip wear (they were well over 10 years old...)

 



After new probe installation, the monitor indicated a 10 degree drop in CHTs, but still running well over 430 in cruise...

Last weekend, I re-routed the heater duct away and around the exit ramps.  A pain, but just took some time and extra materials.  Noticed an immediate improvement in cooling, but CHTs were still too high for my liking.

 



I ordered a Mag-Rite timing tool kit from ATS.  Digital protractor and nylon cylinder probe to enable very precise location of actual TDC (as opposed to a mark on a ring and location on case.)  Can't say enough good things about this kit (worth every penny), very easy to use, and the digital protractor has 1/10 degree resolution.  Re-timed my mags (I have a LASAR ignition) to specs.  To say the timing was 'off' is an understatement.  It was WAY off.  The smoothness of the LASAR masked the issue well, and the motor put out good power.

 



Now that it is 'dialed in' to within a tenth of a degree of accuracy, the CHTs dropped over 20F.

So, I improved cooling air flow, and fixed my timing.  This is AFTER paying an IA for a complete annual, and coming back for troubleshooting.

 



At the end of the day, the lesson I learned is after over 10 years of ownership, I will know when 33R is "dialed in" or not regardless of what an IA may believe even if he has been taking care of this aircraft for several years... Mark

 

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jwellum(at)AOL.COM
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Posted: Mon Apr 23, 2012 6:22 am Post subject: High CHTs Epilogue

The only time that I have seen temps over 400 degrees has been on newly  installed cylinders and I have never seen the oil temp above 195. Typically see  375 on the hottest cylinder on a HOT day. Saturday morning was cool at about 50  degrees. I don't think the hottest cylinder made it to 360 degrees. That was at  2000 feet, leaned out, straight and level at 2700 rpm. Our plane  has an EI, 4 probe  CHT/EGT gauge which probably reads less  than a JPI. Number 2 cylinder is always the coldest at about 320 degrees and  sometimes I think it runs too cold. 

  

  

  

  

  

  

  

  

  

  In a message dated 4/21/2012 11:53:32 P.M. Central Daylight Time,  teamgrumman(at)yahoo.com writes:

  	  Quote: 	
		     Mark,

   



   That's good to hear. When my plane is "dialed in" it will still run 410    straight and level at 4000 feet. Can't wait to get the IO360 on and    finished. 



   Gary

Sent from my iPad

   

On Apr 21, 2012, at 6:30 PM, "Mark T. Mueller" <mark.t.mueller(at)comcast.net (mark.t.mueller(at)comcast.net)>    wrote:

   

    	  Quote: 	
		       A few weeks ago I asked for advice/comments on high CHTs after my      annual inspection.  I appreciate the responses I got back, and most      concentrated on baffling and timing.      



     My IA swore the timing on the engine was correct, and the cabin heating      duct in front of the exit ramp would not effect cooling flow much.       Spent a day trying to troubleshoot, and he became convinced it was an      instrumentation issue.  Kind of made sense, but I was skeptical.       He did find one of the CHT probes had significant tip wear (they were      well over 10 years old...)

     



     After new probe installation, the monitor indicated a 10 degree drop in      CHTs, but still running well over 430 in cruise...

     



     Last weekend, I re-routed the heater duct away and around the exit      ramps.  A pain, but just took some time and extra materials.       Noticed an immediate improvement in cooling, but CHTs were still too      high for my liking.

     



     I ordered a Mag-Rite timing tool kit from ATS.  Digital protractor      and nylon cylinder probe to enable very precise location of actual TDC (as      opposed to a mark on a ring and location on case.)  Can't say enough      good things about this kit (worth every penny), very easy to use, and the      digital protractor has 1/10 degree resolution.  Re-timed my mags (I      have a LASAR ignition) to specs.  To say the timing was 'off' is an      understatement.  It was WAY off.  The smoothness of the LASAR      masked the issue well, and the motor put out good power.

     



     Now that it is 'dialed in' to within a tenth of a degree of accuracy,      the CHTs dropped over 20F.

     



     So, I improved cooling air flow, and fixed my timing.  This is      AFTER paying an IA for a complete annual, and coming back      for troubleshooting.

     



     At the end of the day, the lesson I learned is after over 10 years of      ownership, I will know when 33R is "dialed in" or not regardless of what an      IA may believe even if he has been taking care of this aircraft for several      years...Mark



 	  Quote: 	
		  



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href="http://forums.matronics.com">http://forums.matronics.com

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



	






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 [quote][b]

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teamgrumman(at)yahoo.com
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Posted: Mon Apr 23, 2012 9:22 am Post subject: High CHTs Epilogue

Based on a year of flying with an EI mounted above my JPI, I'd have to say that if you saw CHTs anywhere near 400 on an EI, be worried.  A JPI would be showing over 470 at that point.

        From: "jwellum(at)AOL.COM" <jwellum(at)AOL.COM>

 To: teamgrumman-list(at)matronics.com 

 Sent: Monday, April 23, 2012 7:20 AM

 Subject: Re: High CHTs  Epilogue

  

 

         

 The only time that I have seen temps over 400 degrees has been on newly  installed cylinders and I have never seen the oil temp above 195. Typically see  375 on the hottest cylinder on a HOT day. Saturday morning was cool at about 50  degrees. I don't think the hottest cylinder made it to 360 degrees. That was at  2000 feet, leaned out, straight and level at 2700 rpm. Our plane  has an EI, 4 probe  CHT/EGT gauge which probably reads less  than a JPI. Number 2 cylinder is always the coldest at about 320 degrees and  sometimes I think it runs too cold. 

  

  

  

  

  

  

  

  

  

  In a message dated 4/21/2012 11:53:32 P.M. Central Daylight Time,  teamgrumman(at)yahoo.com writes:

  	  Quote: 	
		     Mark,

   



   That's good to hear. When my plane is "dialed in" it will still run 410    straight and level at 4000 feet. Can't wait to get the IO360 on and    finished. 



   Gary

Sent from my iPad

   

On Apr 21, 2012, at 6:30 PM, "Mark T. Mueller" <mark.t.mueller(at)comcast.net (mark.t.mueller(at)comcast.net)>    wrote:

       	  Quote: 	
		       A few weeks ago I asked for advice/comments on high CHTs after my      annual inspection.  I appreciate the responses I got back, and most      concentrated on baffling and timing.      



     My IA swore the timing on the engine was correct, and the cabin heating      duct in front of the exit ramp would not effect cooling flow much.       Spent a day trying to troubleshoot, and he became convinced it was an      instrumentation issue.  Kind of made sense, but I was skeptical.       He did find one of the CHT probes had significant tip wear (they were      well over 10 years old...)

     



     After new probe installation, the monitor indicated a 10 degree drop in      CHTs, but still running well over 430 in cruise...

     



     Last weekend, I re-routed the heater duct away and around the exit      ramps.  A pain, but just took some time and extra materials.       Noticed an immediate improvement in cooling, but CHTs were still too      high for my liking.

     



     I ordered a Mag-Rite timing tool kit from ATS.  Digital protractor      and nylon cylinder probe to enable very precise location of actual TDC (as      opposed to a mark on a ring and location on case.)  Can't say enough      good things about this kit (worth every penny), very easy to use, and the      digital protractor has 1/10 degree resolution.  Re-timed my mags (I      have a LASAR ignition) to specs.  To say the timing was 'off' is an      understatement.  It was WAY off.  The smoothness of the LASAR      masked the issue well, and the motor put out good power.

     



     Now that it is 'dialed in' to within a tenth of a degree of accuracy,      the CHTs dropped over 20F.

     



     So, I improved cooling air flow, and fixed my timing.  This is      AFTER paying an IA for a complete annual, and coming back      for troubleshooting.

     



     At the end of the day, the lesson I learned is after over 10 years of      ownership, I will know when 33R is "dialed in" or not regardless of what an      IA may believe even if he has been taking care of this aircraft for several      years...Mark



 	  Quote: 	
		  


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Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Mon Apr 23, 2012 8:46 pm Post subject: High CHTs Epilogue

I think you may be right about 320  being too cool. It seems my engine performs best when CHT's are in the 370 - 385  range when set for best power

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