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Problems with High EGT readings

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scc_ron(at)yahoo.com
Guest

Posted: Fri Aug 25, 2006 12:54 pm Post subject: Problems with High EGT readings

Hey all,

I've just begun to have 1450+ EGT readings on all cylinders, while the CHT's remain below 390 degrees. No attempt to richen things up (carb heat for example) improves things. I took off the cowl and see no exterior signs of trouble, removed spark plugs and they are nice and tan and even wet from running too rich. I tried a brief flight and all was normal, then on the next long leg they did it again. I recycled the Grand Rapids EIS and then only one cylinder persisted in giving me this reading. Am I right to assume it is an indicator/gauge issue or am I missing something more ominous?

Thanks in advance for your ideas.

Ron

RV-4 N8ZD [quote][b]

brian-av(at)lloyd.com
Guest

Posted: Fri Aug 25, 2006 4:37 pm Post subject: Problems with High EGT readings

On Aug 25, 2006, at 1:52 PM, Ron Patterson wrote:



 	  Quote: 	
		   Hey all,

 I've just begun to have 1450+ EGT readings on all cylinders, while  

 the CHT's remain below 390 degrees. No attempt to richen things up  

 (carb heat for example) improves things. I took off the cowl and  

 see no exterior signs of trouble, removed spark plugs and they are  

 nice and tan and even wet from running too rich. I tried a brief  

 flight and all was normal, then on the next long leg they did it  

 again. I recycled the Grand Rapids EIS and then only one cylinder  

 persisted in giving me this reading. Am I right to assume it is an  

 indicator/gauge issue or am I missing something more ominous?


	


If you have a sudden high EGT on all cylinders, check to see if one  

mag has stopped working. If both mags are normal and CHTs are normal,  

look for a gauge problem.



Brian Lloyd                         361 Catterline Way

brian HYPHEN av AT lloyd DOT com    Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

FLYaDIVE(at)aol.com
Guest

Posted: Fri Aug 25, 2006 6:02 pm Post subject: Problems with High EGT readings

In a message dated 8/25/06 8:41:24 PM Eastern Daylight Time, 

brian-av(at)lloyd.com writes:



 	  Quote: 	
		   If you have a sudden high EGT on all cylinders, check to see if one  

  mag has stopped working. If both mags are normal and CHTs are normal,  

  look for a gauge problem.

=================================
	


Brian:



If you reduce your spark in half your EGT goes DOWN not UP.  Loss of a Mag 

reduces combustion efficiency.  If the timing is incorrect EGT can go UP but 

usually the Oil and CHT follows.

Ron said CHT was 390 F but he did not say that was his NORMAL ... Only that 

is below 390F.



What Ron should be looking for is something that will cause LEANING ... 

either Less Fuel or More Air.  

My first place to look would be an AIR LEAK around the Carb.  

Second place would be the rubber coupling on the intake, but the chances of 

that are very slim since ALL cylinder increased EGT.  

Third place is an EXHAUST Leak.  Around the flanges ... Ron, you didn't use 

those cheep soft exhaust gaskets?

I have a very difficult time believing that all 4 EGT probes drifted in the 

same direction.  Or that the EIS failed in such a manor that ONLY the EGT was 

affected and not the CHT.



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

Jim Baker

Joined: 30 Mar 2006
Posts: 181
Location: Sayre, PA

Posted: Fri Aug 25, 2006 6:32 pm Post subject: Problems with High EGT readings

 	  Quote: 	
		   If you reduce your spark in half your EGT goes DOWN not UP.  

Loss of a
	


 	  Quote: 	
		   Mag reduces combustion efficiency. 


	




Nope. EGT should rise about 50 degrees F on all cylinders. Think a 

bit more about this and you'll understand why it work this way....



Jim Baker

580.788.2779

'71 SV,  492TC

Elmore City, OK

flyeyes(at)mac.com
Guest

Posted: Fri Aug 25, 2006 6:45 pm Post subject: Problems with High EGT readings

On Aug 25, 2006, at 3:52 PM, Ron Patterson wrote:

 	  Quote: 	
		  Hey all,

I've just begun to have 1450+ EGT readings on all cylinders, while the CHT's remain below 390 degrees. No attempt to richen things up (carb heat for example) improves things. I took off the cowl and see no exterior signs of trouble, removed spark plugs and they are nice and tan and even wet from running too rich. I tried a brief flight and all was normal, then on the next long leg they did it again. I recycled the Grand Rapids EIS and then only one cylinder persisted in giving me this reading. Am I right to assume it is an indicator/gauge issue or am I missing something more ominous?

Thanks in advance for your ideas.

Ron

RV-4 N8ZD 	


 

Hi Ron



As Brian mentioned, loss of one ignition will cause all the EGTs to rise simultaneously, along with a small loss of power and slightly lower CHTs.  I have had these exact symptoms caused by an ignition failure in the climb--I noticed it when EGTs went well above their normal peaks as I tried to lean.  You can diagnose this quickly by cycling the mags in the air, but this is probably best done without your wife in the back seat (or so I've heard.  At length.).



I think it's most likely an indicator issue, but would check ignition first.  I have a vague recollection of reading about similar symptoms with an EIS with a wiring issue sometime in the last few weeks.  You might  want to try Greg at Grand Rapids--he seems to be pretty responsive.  A search of the various RV/aerolelectric forums and Doug's VAF site for "EIS" and "EGT" might turn up some relevant posts.



James Freeman

 [quote][b]

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Fri Aug 25, 2006 6:49 pm Post subject: Problems with High EGT readings

Sorry Barry, but Brian is correct. Demonstrable on any mag check during 

run up or an in flight mag check. The flame front propagates slower with 

single ignition, and burns longer in the cylinder, making it hotter 

coming out the exhaust.

FLYaDIVE(at)aol.com wrote:

 	  Quote: 	

 In a message dated 8/25/06 8:41:24 PM Eastern Daylight Time, 

 brian-av(at)lloyd.com writes:

> If you have a sudden high EGT on all cylinders, check to see if one  

>  mag has stopped working. If both mags are normal and CHTs are normal,  

>  look for a gauge problem.

 =================================

 Brian:

 If you reduce your spark in half your EGT goes DOWN not UP.  Loss of a Mag 

 reduces combustion efficiency.  If the timing is incorrect EGT can go UP but 

 usually the Oil and CHT follows.

 Ron said CHT was 390 F but he did not say that was his NORMAL ... Only that 

 is below 390F.

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

oldbob(at)beechowners.com
Guest

Posted: Fri Aug 25, 2006 7:14 pm Post subject: Problems with High EGT readings

Good Evening Barry,

May I suggest that you rethink that a bit?

When operating on one magneto, the EGTs will rise.

Why?

Because the timing is effectively retarded and the

peak temperature occurs later in the combustion cycle.

The fire gets closer to the point where it is

measured. The actual peak combustion pressure and

temperature will both be lower, but due to the timing

change, the EGTs Will be higher.

Happy Skies,

Old Bob

--- FLYaDIVE(at)aol.com wrote:

 	  Quote: 	

 FLYaDIVE(at)aol.com

 In a message dated 8/25/06 8:41:24 PM Eastern

 Daylight Time, 

 brian-av(at)lloyd.com writes:

 > If you have a sudden high EGT on all cylinders,

 check to see if one  

 >  mag has stopped working. If both mags are normal

 and CHTs are normal,  

 >  look for a gauge problem.

 =================================

 Brian:

 If you reduce your spark in half your EGT goes DOWN

 not UP.  Loss of a Mag 

 reduces combustion efficiency.  If the timing is

 incorrect EGT can go UP but 

 usually the Oil and CHT follows.

 Ron said CHT was 390 F but he did not say that was

 his NORMAL ... Only that 

 is below 390F.

 What Ron should be looking for is something that

 will cause LEANING ... 

 either Less Fuel or More Air.  

 My first place to look would be an AIR LEAK around

 the Carb.  

 Second place would be the rubber coupling on the

 intake, but the chances of 

 that are very slim since ALL cylinder increased EGT.

 Third place is an EXHAUST Leak.  Around the flanges

 ... Ron, you didn't use 

 those cheep soft exhaust gaskets?

 I have a very difficult time believing that all 4

 EGT probes drifted in the 

 same direction.  Or that the EIS failed in such a

 manor that ONLY the EGT was 

 affected and not the CHT.

 Barry

 "Chop'd Liver"

 "Show them the first time, correct them the second

 time, kick them the third 

 time." 

 Yamashiada

 browse

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 Admin.

altoq(at)cebridge.net
Guest

Posted: Fri Aug 25, 2006 7:14 pm Post subject: Problems with High EGT readings

Barry,

I always get in trouble when I do this but, here goes.  By eliminating one 

of two firing positions, You effectively retard timing because Peak BMEP 

occurs later. Combustion is incomplete, some of what does not burn in the 

chamber, burns in the exhaust pipes, hence, higher EGT. CHT may or may not 

be lower (depends on too many other things). I would initially look for a 

primary ignition fault.

John D.



DO NOT ARCHIVE



 	  Quote: 	
		   Brian:



 If you reduce your spark in half your EGT goes DOWN not UP.  Loss of a Mag

 reduces combustion efficiency.  If the timing is incorrect EGT can go UP 

 but

 usually the Oil and CHT follows.

 Ron said CHT was 390 F but he did not say that was his NORMAL ... Only 

 that

 is below 390F.



 What Ron should be looking for is something that will cause LEANING ...

 either Less Fuel or More Air.

 My first place to look would be an AIR LEAK around the Carb.

 Second place would be the rubber coupling on the intake, but the chances 

 of

 that are very slim since ALL cylinder increased EGT.

 Third place is an EXHAUST Leak.  Around the flanges ... Ron, you didn't 

 use

 those cheep soft exhaust gaskets?

 I have a very difficult time believing that all 4 EGT probes drifted in 

 the

 same direction.  Or that the EIS failed in such a manor that ONLY the EGT 

 was

 affected and not the CHT.



 Barry

 "Chop'd Liver"

mprather(at)spro.net
Guest

Posted: Fri Aug 25, 2006 7:33 pm Post subject: Problems with High EGT readings

Turning off one mag slows down the combustion process - effectively

retarding the spark timing.  That will cause the EGT to rise because more

of the fuel air mixture will be left burning when the exhaust valve opens.

 Cylinder pressure WILL be lower..

See John Deak and George Braly for more info.  Or..  Try it on your plane.

Regards,

Matt-

FLYaDIVE(at)aol.com wrote:

 	  Quote: 	

In a message dated 8/25/06 8:41:24 PM Eastern Daylight Time,

brian-av(at)lloyd.com writes:

>If you have a sudden high EGT on all cylinders, check to see if one

> mag has stopped working. If both mags are normal and CHTs are normal,

> look for a gauge problem.

=================================

Brian:

If you reduce your spark in half your EGT goes DOWN not UP.  Loss of a Mag

reduces combustion efficiency.  If the timing is incorrect EGT can go UP but

usually the Oil and CHT follows.

Ron said CHT was 390 F but he did not say that was his NORMAL ... Only that

is below 390F.

What Ron should be looking for is something that will cause LEANING ...

either Less Fuel or More Air.

My first place to look would be an AIR LEAK around the Carb.

Second place would be the rubber coupling on the intake, but the chances of

that are very slim since ALL cylinder increased EGT.

Third place is an EXHAUST Leak.  Around the flanges ... Ron, you didn't use

those cheep soft exhaust gaskets?

I have a very difficult time believing that all 4 EGT probes drifted in the

same direction.  Or that the EIS failed in such a manor that ONLY the EGT

was

 	  Quote: 	
		  affected and not the CHT.

Barry

"Chop'd Liver"

"Show them the first time, correct them the second time, kick them the third

time."

Yamashiada

brian-av(at)lloyd.com
Guest

Posted: Fri Aug 25, 2006 7:47 pm Post subject: Problems with High EGT readings

On Aug 25, 2006, at 6:59 PM, FLYaDIVE(at)aol.com wrote:

 	  Quote: 	

 In a message dated 8/25/06 8:41:24 PM Eastern Daylight Time,

 brian-av(at)lloyd.com writes:

> If you have a sudden high EGT on all cylinders, check to see if one

>  mag has stopped working. If both mags are normal and CHTs are  

> normal,

>  look for a gauge problem.

 =================================

 Brian:

 If you reduce your spark in half your EGT goes DOWN not UP.

Normally I try to be diplomatic but in this case I will make an  

exception. You are just plain wrong.

Proof:

Turn off one mag in cruise and watch your EGT go up by about 100F.

Reason:

With both mags working you have two flame-fronts in the combustion  

chamber. This means that combustion completes sooner allowing more  

time for the gas to transfer heat to the components in the cylinder  

thus leading to cooler gas going out the exhaust. When you turn off  

one mag you have only one flame front and the combustion time is  

slightly longer. There is now less time after the end of combustion  

and before the exhaust valve opens so your EGT is higher.

 	  Quote: 	
		   Loss of a Mag reduces combustion efficiency.

Yeah, so?

 	  Quote: 	
		   If the timing is incorrect EGT can go UP but

 usually the Oil and CHT follows.

Actually, if you get advanced timing your CHT will go up but your EGT  

will go down for the reasons I outlined above. Detonation will do the  

same thing.

 	  Quote: 	
		   Ron said CHT was 390 F but he did not say that was his NORMAL ...  

 Only that

 is below 390F.

I read that to mean that he did not see an increase in CHT.

 	  Quote: 	

 What Ron should be looking for is something that will cause  

 LEANING ...

Perhaps. The simplest explanation for a 100F rise in EGT across all  

cylinders without a rise in CHT is the loss of a mag. (Actually CHT  

will drop slightly as less heat is transferred to the head.) It is  

also pitifully easy to check. After that it is time for more  

difficult tests and inspections.

Brian Lloyd                         361 Catterline Way

brian HYPHEN av AT lloyd DOT com    Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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