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In Flight CHT's

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richardranger(at)ozemail.
Guest

Posted: Thu Sep 17, 2015 1:51 am Post subject: In Flight CHT's

Gary, you have raised some very interesting issues on your flight to SLC, and I hope it stimulates good discussion.

Firstly, your hotted up engine does not sound as though it is yet run-in. The CHT's you observed are very high and consistent with a new powerplant. From my own experience, it took 30 hours at 75 percent power and very high (and expensive) fuel flows for the CHT's to settle below 400 F in cruise and for oil consumption to fall. They are now consistently between 360 and 390 at 65 percent power, with oil consumption minimal.

At standard atmosphere 75 pc power can only be achieved with wide open throttle (WOT) at 8,000 ft and less if the temp is higher; so that is probably the maximum altitude to bed in the engine. At 12,500 ft and WOT max power is only 63 percent, which is a power setting that should never damage an engine according to Lycoming, but is below 'running in power' settings.

That you can achieve such high CHT's at 12,500 ft is concerning, given the limited power at that altitude, and their variability without changing mixture or throttle setting is strange. Timing issues or preignition need to be excluded.

You are correct in saying that engines without 4 cyl monitoring may be running temperatures way out 'normal', yet they seem to run OK. Are we being over careful?



Richard Ranger

AA5b



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flying-nut(at)cfl.rr.com
Guest

Posted: Thu Sep 17, 2015 7:33 am Post subject: In Flight CHT's

I'm no expert but have had good breakin results using WOT around 3000 

AGL.  I expect CHTs to be higher than normal and use mixture/throttle to 

try and keep them below 450.  The hottest may go above, but not for 

long.  Flights at least an hour at a time.



You have to remember that the numbers Lycoming uses are set for an 

engine during certification, and by nature are conservative.  I learned 

a lot during an off-the-record discussion with a Lycoming engineer.  

Early in the discussion his comment was 'you can't do that' but when 

off-the-record he opened up.

Linn



On 9/17/2015 5:51 AM, Richard Ranger wrote:

 	  Quote: 	
		   



 Gary, you have raised some very interesting issues on your flight to SLC, and I hope it stimulates good discussion.

 Firstly, your hotted up engine does not sound as though it is yet run-in. The CHT's you observed are very high and consistent with a new powerplant. From my own experience, it took 30 hours at 75 percent power and very high (and expensive) fuel flows for the CHT's to settle below 400 F in cruise and for oil consumption to fall. They are now consistently between 360 and 390 at 65 percent power, with oil consumption minimal.

 At standard atmosphere 75 pc power can only be achieved with wide open throttle (WOT) at 8,000 ft and less if the temp is higher; so that is probably the maximum altitude to bed in the engine. At 12,500 ft and WOT max power is only 63 percent, which is a power setting that should never damage an engine according to Lycoming, but is below 'running in power' settings.

 That you can achieve such high CHT's at 12,500 ft is concerning, given the limited power at that altitude, and their variability without changing mixture or throttle setting is strange. Timing issues or preignition need to be excluded.

 You are correct in saying that engines without 4 cyl monitoring may be running temperatures way out 'normal', yet they seem to run OK. Are we being over careful?



 Richard Ranger

 AA5b



 Sent from my iPad

 -----

 No virus found in this message.

 Checked by AVG - www.avg.com

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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BILL9725(at)AOL.COM
Guest

Posted: Thu Sep 17, 2015 9:18 am Post subject: In Flight CHT's

Hi Everyone 

  

 Have to add my two cents on this.  I just came back from Carson City  to the Central Valley with my Tiger and while cruising   at 12,500 with  very above normal outside temps, valley was over 100 that day, 12,500 was 17 C,  and thanks to Gary`s cowling, fine wire plugs and the Power flow was showing max  CHT`s at 406 for number 3 & 4 390 for 1 & 2, RPM 2675.  Leaned to  peak, Electronic Tac and JPI.

  

   Best news here is I still had over 1 Inch of throttle left and it  would red line over 2700 easily.  So I can say temps can be  controlled.  Density altitude was 15,000 so I know it is not the usual 360  but wanted to add that you can control temps. 

  

 Thanks 

  

 Bill Stigle 

  

  In a message dated 9/17/2015 8:33:44 A.M. Pacific Daylight Time,  flying-nut(at)cfl.rr.com writes:

  	  Quote: 	
		  -->    TeamGrumman-List message posted by: Linn Walters    <flying-nut(at)cfl.rr.com>



I'm no expert but have had good breakin    results using WOT around 3000 

AGL.  I expect CHTs to be higher than    normal and use mixture/throttle to 

try and keep them below 450.  The    hottest may go above, but not for 

long.  Flights at least an hour at    a time.



You have to remember that the numbers Lycoming uses are set for    an 

engine during certification, and by nature are conservative.  I    learned 

a lot during an off-the-record discussion with a Lycoming    engineer.  

Early in the discussion his comment was 'you can't do    that' but when 

off-the-record he opened up.

Linn



On 9/17/2015    5:51 AM, Richard Ranger wrote:

 	  Quote: 	
		   --> TeamGrumman-List message posted    by: Richard Ranger <richardranger(at)ozemail.com.au>



 Gary,    you have raised some very interesting issues on your flight to SLC, and I hope    it stimulates good discussion.

 Firstly, your hotted up engine does not    sound as though it is yet run-in. The CHT's you observed are very high and    consistent with a new powerplant. From my own experience, it took 30 hours at    75 percent power and very high (and expensive) fuel flows for the CHT's to    settle below 400 F in cruise and for oil consumption to fall. They are now    consistently between 360 and 390 at 65 percent power, with oil consumption    minimal.

 At standard atmosphere 75 pc power can only be achieved with    wide open throttle (WOT) at 8,000 ft and less if the temp is higher; so that    is probably the maximum altitude to bed in the engine. At 12,500 ft and WOT    max power is only 63 percent, which is a power setting that should never    damage an engine according to Lycoming, but is below 'running in power'    settings.

 That you can achieve such high CHT's at 12,500 ft is    concerning, given the limited power at that altitude, and their variability    without changing mixture or throttle setting is strange. Timing issues or    preignition need to be excluded.

 You are correct in saying that    engines without 4 cyl monitoring may be running temperatures way out 'normal',    yet they seem to run OK. Are we being over careful?



 Richard    Ranger

 AA5b



 Sent from my    iPad

 -----

 No    virus found in this message.

 Checked by AVG -  ================================================= Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================


	


	


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