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EGT Probes

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cffd(at)pgrb.com
Guest

Posted: Sat Feb 09, 2008 7:04 am Post subject: EGT Probes

I am going to add EGT's to my 2200 (SN 988).

I  can get probes that are either 1/2 inch long or 1 inch long.

Any comments on  which length should I get? 



 Chuck D.



   [quote][b]

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andy(at)suncoastjabiru.co
Guest

Posted: Sat Feb 09, 2008 7:44 am Post subject: EGT Probes

Chuck,  

   

Get the 1” ones; they’ll span the inside diameter of the exhaust pipes nicely.  

   

Andy Silvester  

Suncoast Sportplanes, Inc  

813 377 2716  

       

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of Chuck Deiterich

 Sent: 09 February 2008 12:59

 To: Jab-list

 Subject: EGT Probes  

  

  

     

I am going to add EGT's to my 2200 (SN 988).

 I can get probes that are either 1/2 inch long or 1 inch long.

 Any comments on which length should I get?   

    

Chuck D.  

  

       [quote][b]

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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sat Feb 09, 2008 12:12 pm Post subject: EGT Probes

Andy-

Wouldn't you want the tip of the probe to be in the center of the  

pipe? It's been my experience (a few years spent installing  

thermocouples in test cars for Chrysler Corp) that it's where the two  

dissimilar wires come together...usually at the tip of the  

thermocouple...that the reading is made. I'll certainly defer to your  

knowledge of the thermocouples in question....I know nothing about  

those particular ones.



Lynn Matteson

Grass Lake, Michigan

Kitfox IV Speedster  w/Jabiru 2200

flying w/470+ hrs

On Feb 9, 2008, at 10:39 AM, Andy Silvester wrote:



 	  Quote: 	
		   Chuck,



 Get the 1” ones; they’ll span the inside diameter of the exhaust  

 pipes nicely.



 Andy Silvester



 Suncoast Sportplanes, Inc



 813 377 2716



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

 jabiruengine-list-server(at)matronics.com] On Behalf Of Chuck Deiterich

 Sent: 09 February 2008 12:59

 To: Jab-list

 Subject: EGT Probes



 I am going to add EGT's to my 2200 (SN 988).

 I can get probes that are either 1/2 inch long or 1 inch long.

 Any comments on which length should I get?



 Chuck D.



 forums.matronics.com_- 

 ============================================================ _- 

 contribution_- 

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

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

andy(at)suncoastjabiru.co
Guest

Posted: Sun Feb 10, 2008 4:49 am Post subject: EGT Probes

Lynn,



I think you probably have the 'edge' over me on thermocouple technology, but

with these EGT senders, you're attempting to measure a pipe full of very

fast moving hot gas and I doubt, with the turbulence of post-combustion,

anyone can really tell where (in the pipe diameter) the best place for true

measurement is. Unless of course you could spend considerable time in

laboratory conditions measuring.....We've always used the 1" probes,

supplied mainly from Grand Rapids Technologies and as a measure of EGT, they

do a fair job. After all, EGT is very much a 'comparative' measurement and

it's always the case to see a wider range of temps across all cylinders,

(even when in the case of a direct-injected engine where mixture is more

accurately known), than you'd see for example in a well-balanced set of CHT

figures. What you'll be looking for is a temperature span of less than (say)

80F-100F across cylinders (less is good but often not worth chasing), but

the absolute values will tell you more about how the engine's doing:



1. Less than 1100F will betray an over-rich condition

2. Above 1400F is too lean, particularly at full throttle.



Remember, the Bing's mixture compensating needle will promote a relatively

rich mixture at high throttle openings (so the high workload won't lead to

detonation) and a relatively lean condition in the cruise. Prop selection,

airframe type, fuel quality all have effects, but essentially I get my

confidence from a good-running engine by seeing (say) cruise EGTs around

1250F-1300F, and wide-open throttle EGTs about 100F less. Opening the

throttle to full while monitoring the EGTs will see a marked reduction.

Comprehensive info on this subject can be found in Jabiru's Service Bulletin

JSB 018-1 at:

http://www.jabiru.net.au/Service%20Bulletins/Engine%20files/JSB018-1Engine%2

0tuning.pdf



There's plenty of accepted wisdom about the benefits of multiple EGT

measurement; noting a rising EGT on a cylinder could help to diagnose an

air-leak in the induction and signal the need for maintenance before an

expensive head overhaul becomes necessary. Thanks, Lynn for providing the

opportunity to neatly evade your topic and (no doubt) raise discussion about

another..!



Cheers, Andy

Suncoast Sportplanes, Inc.



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Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Sun Feb 10, 2008 8:35 am Post subject: EGT Probes

Thanks for the info, Andy. I've got all four cyls monitored with  

Grand Rapids Technologies probes, and their EIS. I'm not sure what  

length they are, but I recall having to stack about 1/8" of washers  

onto the probe so as to prevent it from entering the pipe too far. I  

can't really recall where this put the probe in relationship to the  

center of the pipe...maybe it just kept it from touching the other  

side of the pipe, which wouldn't be good for readings.



My particular readings are in the 1300's F at full throttle, all  

within 40F, and in the 1400's F at cruise. I've got engine #2062  

which had the economy tune at the time of delivery, and I haven't  

changed it. Sounds like maybe I'd better go a little richer, eh?



Lynn Matteson

Grass Lake, Michigan

Kitfox IV Speedster  w/Jabiru 2200

flying w/470+ hrs



On Feb 10, 2008, at 7:44 AM, Andy Silvester wrote:



 	  Quote: 	
		   

 <andy(at)suncoastjabiru.com>



 Lynn,



 I think you probably have the 'edge' over me on thermocouple  

 technology, but

 with these EGT senders, you're attempting to measure a pipe full of  

 very

 fast moving hot gas and I doubt, with the turbulence of post- 

 combustion,

 anyone can really tell where (in the pipe diameter) the best place  

 for true

 measurement is. Unless of course you could spend considerable time in

 laboratory conditions measuring.....We've always used the 1" probes,

 supplied mainly from Grand Rapids Technologies and as a measure of  

 EGT, they

 do a fair job. After all, EGT is very much a 'comparative'  

 measurement and

 it's always the case to see a wider range of temps across all  

 cylinders,

 (even when in the case of a direct-injected engine where mixture is  

 more

 accurately known), than you'd see for example in a well-balanced  

 set of CHT

 figures. What you'll be looking for is a temperature span of less  

 than (say)

 80F-100F across cylinders (less is good but often not worth  

 chasing), but

 the absolute values will tell you more about how the engine's doing:



 1. Less than 1100F will betray an over-rich condition

 2. Above 1400F is too lean, particularly at full throttle.



 Remember, the Bing's mixture compensating needle will promote a  

 relatively

 rich mixture at high throttle openings (so the high workload won't  

 lead to

 detonation) and a relatively lean condition in the cruise. Prop  

 selection,

 airframe type, fuel quality all have effects, but essentially I get my

 confidence from a good-running engine by seeing (say) cruise EGTs  

 around

 1250F-1300F, and wide-open throttle EGTs about 100F less. Opening the

 throttle to full while monitoring the EGTs will see a marked  

 reduction.

 Comprehensive info on this subject can be found in Jabiru's Service  

 Bulletin

 JSB 018-1 at:

 http://www.jabiru.net.au/Service%20Bulletins/Engine%20files/ 

 JSB018-1Engine%2

 0tuning.pdf



 There's plenty of accepted wisdom about the benefits of multiple EGT

 measurement; noting a rising EGT on a cylinder could help to  

 diagnose an

 air-leak in the induction and signal the need for maintenance  

 before an

 expensive head overhaul becomes necessary. Thanks, Lynn for  

 providing the

 opportunity to neatly evade your topic and (no doubt) raise  

 discussion about

 another..!



 Cheers, Andy

 Suncoast Sportplanes, Inc.

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_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

andy(at)suncoastjabiru.co
Guest

Posted: Sun Feb 10, 2008 3:24 pm Post subject: EGT Probes

Lynn,



Actually, those temps and 'span' are very good; I wouldn't change a thing,

particularly on the 2200. I have run our own engines hotter (in the 1400s at

cruise) and with no ill-effects in a few hundred hours, but it's a little

higher than Jabiru's own recommendations. As long as you're seeing that drop

on increase in throttle, you're good with what you have, and no doubt a

pretty good g.p.h. figure.



Andy



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plus2s

Joined: 30 Nov 2006
Posts: 65
Location: NEW ZEALAND

Posted: Sun Feb 10, 2008 3:40 pm Post subject: EGT Probes

Wasn't there a recommendation to drill the main jet out slightly on the

tuning kit ?



Keith



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cffd(at)pgrb.com
Guest

Posted: Sun Feb 10, 2008 5:44 pm Post subject: EGT Probes

Andy and Lynn,



Thanks for the response.

I searched around the internet and also looked at Tony Bingelis' books.

His book  just has a drawing that shows the tip of the probe in  the center.

One place said the tip should be in the center of the gas stream

I suspect in the center is the hottest.

So that is what I will try to do.



Chuck D.

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