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wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Dec 28, 2006 3:18 pm Post subject: Possible overheating and EGT question

I discovered a small puddle of coolant under my airplane this morning. I had spent the previous day practicing in the pattern for almost two hours and Iâ€™m wondering if the constant "touch & go" with all that time at full throttle caused it to overheat. I'm ashamed to say that I did not notice if any of the gauges where indicating anything out of the ordinary. 



I ran her up on the ground for a while and could not reproduce the leak so I tried a few turns around the pattern keeping a close eye on the gauges. As usual the EGT runs near the upper range of the gauge during takeoff at 1600F. I didn't used to worry about that because it's still just shy of max and it always cools off once I level out for cruise. Today though, I noticed that it stayed up at 1600 on the downwind leg coming down only when I pulled back to idle before the base turn.



Is this normal behavior for EGT? Should I bump the mixture a bit? If I do adjust the mixture, how do I keep the two carbs in sync?

eskflyer(at)lvcisp.com
Guest

Posted: Thu Dec 28, 2006 4:53 pm Post subject: Possible overheating and EGT question

UHHHH   Wing nut what engine are you running .

If you are running the 582 you most likely have a fried engine MAX EGT is 

1200 .

If 912 normal is 1472 max is 1652

Good luck and hope you find the trouble



John Perry



DO NOT ARCHIVE

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Dec 28, 2006 5:47 pm Post subject: Re: Possible overheating and EGT question

Duh. Sorry 912UL.

Is it typical for EGT to hit max at full throttle? Water and oil temps are nominal as is oil pressure. Another thing worries me is that this Westach combo gauge only goes up to 1600F. It looks like the needle is free to move beyond 1600 but there's no way to be sure.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Thu Dec 28, 2006 6:35 pm Post subject: Possible overheating and EGT question

Sounds like you might be a bit lean.  Also the cool dense air is making your

engine run even leaner.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Thu Dec 28, 2006 6:55 pm Post subject: Possible overheating and EGT question

Hi Luis, (not sure about your name)



Funny this thing, as I thought I'll write some- about the EGT system  

before the New Year.  Hmmm...



The thing is that, the EGT system is measuring differential temperature.  

Ok., the system that is used for measuring the exhaust gas temperature is  

measuring temperature difference, NOT absolute temperature!!



Well, it is measuring the temperature difference between the  

cockpit(inside cockpit temperature -NOT the OAT!) and the EGT probe  

temperature.



But you'll know, the temperature in the cockpit may change -then your EGT  

reading change too!!!



To know your correct EGT temperature (at the probe) it important to know  

the cockpit temperature.



So now, I'm wondering   how many of you are using a true cockpit  

thermometer?



Some of you might have the double temperature meter, that measure the  

inside and outside temperature (with ice warning) for cars?



This is indeed a good idea (if you checked that the readings are correct)  

as this can be used to calculate your "true" EGT.



The ting is that, your EGT system is calibrated at a known temperature!   

Do you know this temperature for your instrument???



Now, think about this "calibration temperature" as a line across a  

standard mercury meter scale, if your cockpit temperature is above this  

line -your meter is reading to low!



This is because the meter (and the calibration point) is moving towards  

the EGT probe temperature, see less difference I.E. reading to low.



The other way around, no cockpit heater (or a poor heater), I'm trying to  

say that the cockpit temperature is below the "calibration value".  In  

this case, the indicated value will show to high, so we think that we are  

boosting the red line. But indeed we should subtract the "absolute" value  

of the reading BELOW the "calibration value" line.



In this latter case, our reading will be to high.



Ok., to summarize; in the winter time our reading will be to high, -and in  

the summer time our reading will be to low,  IF OUR COCKPIT TEMPERATURE  

DIFFER/VARY WITH SEASONS FROM THE INSTRUMENTS CALIBRATION TEMPERATURE.



If you have a temperature controlled â€œde luxeâ€ heater that can maintain,  

say 23 deg. Celsius in the cockpit -everything become so much more  

simple.    



(I'll add a little bit more about this later.)



Now to your engine:



Doing touch and go is without doubt a real hard work for your engine, esp.  

in the winter time.



As the temperature is going a lot down, and maybe it's CAVOK(a high  

pressure), in this situ. your engine got lot's of more O2 -meaning better  

combustion and higher temperature. Yes, we've to enrich to keep the  

temperature in the green (one notch up and..).  So this is why we have  

more power during the winter season. (Sure that's more to say here..).



Also, as the air molecules is closer together we would have a better lift  

as well. (Hey, winter flying is more fun!!)



In the winter time, cooling is also allot better, so this will normally  

not occur, unless there is another problem. (If not, check your  

thermostat.)



A last word, after such a hard work for your engine it is a good practice  

to let the engine idle for some time to take the heath out. If not, we  

often see that the engine start boiling after shut down.  (Hint; this is  

always a must for a turbo engine).

Torgeir.



On Fri, 29 Dec 2006 00:18:55 +0100, wingnut <wingnut(at)spamarrest.com> wrote:



 	  Quote: 	
		   



 I discovered a small puddle of coolant under my airplane this morning. I  

 had spent the previous day practicing in the pattern for almost two  

 hours and IÃ¢â‚¬â„¢m wondering if the constant "touch & go" with all that  

 time at full throttle caused it to overheat. I'm ashamed to say that I  

 did not notice if any of the gauges where indicating anything out of the  

 ordinary.



 I ran her up on the ground for a while and could not reproduce the leak  

 so I tried a few turns around the pattern keeping a close eye on the  

 gauges. As usual the EGT runs near the upper range of the gauge during  

 takeoff at 1600F. I didn't used to worry about that because it's still  

 just shy of max and it always cools off once I level out for cruise.  

 Today though, I noticed that it stayed up at 1600 on the downwind leg  

 coming down only when I pulled back to idle before the base turn.



 Is this normal behavior for EGT? Should I bump the mixture a bit? If I  

 do adjust the mixture, how do I keep the two carbs in sync?





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=84061#84061




	


-- 

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

torgemor(at)online.no
Guest

Posted: Thu Dec 28, 2006 9:02 pm Post subject: Possible overheating and EGT question

Hi again,

Just a little important note.

When I said one notch up, I meant one notch to bring the needle up having  

more rich mixture.

To actually do this, the locking ring has to go one notch down on the  

needle itself...

Sorry, but do not want any confusion here.

Torgeir.

On Fri, 29 Dec 2006 03:55:29 +0100, Torgeir Mortensen <torgemor(at)online.no>  

wrote:

 	  Quote: 	

 <torgemor(at)online.no>

 Hi Luis, (not sure about your name)

 Funny this thing, as I thought I'll write some- about the EGT system  

 before the New Year.  Hmmm...

 The thing is that, the EGT system is measuring differential temperature.  

 Ok., the system that is used for measuring the exhaust gas temperature  

 is measuring temperature difference, NOT absolute temperature!!

 Well, it is measuring the temperature difference between the  

 cockpit(inside cockpit temperature -NOT the OAT!) and the EGT probe  

 temperature.

 But you'll know, the temperature in the cockpit may change -then your  

 EGT reading change too!!!

 To know your correct EGT temperature (at the probe) it important to know  

 the cockpit temperature.

 So now, I'm wondering   how many of you are using a true cockpit  

 thermometer?

 Some of you might have the double temperature meter, that measure the  

 inside and outside temperature (with ice warning) for cars?

 This is indeed a good idea (if you checked that the readings are  

 correct) as this can be used to calculate your "true" EGT.

 The ting is that, your EGT system is calibrated at a known temperature!   

 Do you know this temperature for your instrument???

 Now, think about this "calibration temperature" as a line across a  

 standard mercury meter scale, if your cockpit temperature is above this  

 line -your meter is reading to low!

 This is because the meter (and the calibration point) is moving towards  

 the EGT probe temperature, see less difference I.E. reading to low.

 The other way around, no cockpit heater (or a poor heater), I'm trying  

 to say that the cockpit temperature is below the "calibration value".   

 In this case, the indicated value will show to high, so we think that we  

 are boosting the red line. But indeed we should subtract the "absolute"  

 value of the reading BELOW the "calibration value" line.

 In this latter case, our reading will be to high.

 Ok., to summarize; in the winter time our reading will be to high, -and  

 in the summer time our reading will be to low,  IF OUR COCKPIT  

 TEMPERATURE DIFFER/VARY WITH SEASONS FROM THE INSTRUMENTS CALIBRATION  

 TEMPERATURE.

 If you have a temperature controlled â€œde luxeâ€ heater that can maintain,  

 say 23 deg. Celsius in the cockpit -everything become so much more  

 simple.    

 (I'll add a little bit more about this later.)

 Now to your engine:

 Doing touch and go is without doubt a real hard work for your engine,  

 esp. in the winter time.

 As the temperature is going a lot down, and maybe it's CAVOK(a high  

 pressure), in this situ. your engine got lot's of more O2 -meaning  

 better combustion and higher temperature. Yes, we've to enrich to keep  

 the temperature in the green (one notch up and..).  So this is why we  

 have more power during the winter season. (Sure that's more to say  

 here..).

 Also, as the air molecules is closer together we would have a better  

 lift as well. (Hey, winter flying is more fun!!)

 In the winter time, cooling is also allot better, so this will normally  

 not occur, unless there is another problem. (If not, check your  

 thermostat.)

 A last word, after such a hard work for your engine it is a good  

 practice to let the engine idle for some time to take the heath out. If  

 not, we often see that the engine start boiling after shut down.  (Hint;  

 this is always a must for a turbo engine).

 Torgeir.

 On Fri, 29 Dec 2006 00:18:55 +0100, wingnut <wingnut(at)spamarrest.com>  

 wrote:

> 

>

> I discovered a small puddle of coolant under my airplane this morning.  

> I had spent the previous day practicing in the pattern for almost two  

> hours and IÃ¢â‚¬â„¢m wondering if the constant "touch & go" with all that  

> time at full throttle caused it to overheat. I'm ashamed to say that I  

> did not notice if any of the gauges where indicating anything out of  

> the ordinary.

>

> I ran her up on the ground for a while and could not reproduce the leak  

> so I tried a few turns around the pattern keeping a close eye on the  

> gauges. As usual the EGT runs near the upper range of the gauge during  

> takeoff at 1600F. I didn't used to worry about that because it's still  

> just shy of max and it always cools off once I level out for cruise.  

> Today though, I noticed that it stayed up at 1600 on the downwind leg  

> coming down only when I pulled back to idle before the base turn.

>

> Is this normal behavior for EGT? Should I bump the mixture a bit? If I  

> do adjust the mixture, how do I keep the two carbs in sync?

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=84061#84061

>

-- 

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Dec 28, 2006 9:10 pm Post subject: Re: Possible overheating and EGT question

 	  Quote: 	
		  When I said one notch up, I meant one notch to bring the needle up having 

more rich mixture. 



To actually do this, the locking ring has to go one notch down on the 

needle itself... 	


OK. Now I'm really confused. You wouldn't happen to know where I can find an illustration of what you are talking about? Also, when adjusting the mixture at the carb, how does one ensure that the two carbs stay in sync?



-Luis

-824KF

runwayrex(at)juno.com
Guest

Posted: Thu Dec 28, 2006 9:40 pm Post subject: Possible overheating and EGT question

OK. Now I'm really confused. You wouldn't happen to know where I can find an illustration of what you are talking about? Also, when adjusting the mixture at the carb, how does one ensure that the two carbs stay in sync?

 

Luis, 

    Did you get my earlier response (off line)?

    Changing the needle positions on the carbs does not have any affect on the carb syncronization. Check out either the Rotax parts catalog or the overhaul manual. Both show the needle and clip relationship in diagrams. 

Rex in Michigan

-Luis

-824KF





Read this topic online here:



http://forums.matronics.com================================================    - The Kitfox-List Email Foruist utilities such as the Subscriptions pa================================================sp;     - NEW MATRONICS WEB&nbsp=======================================================

   [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Fri Dec 29, 2006 5:58 am Post subject: Possible overheating and EGT question

All you will ever want to know about Rotax engines

http://www.ultralightnews.ca/



There is a diagram on the left side of this page half way down Bing 54



http://www.ultralightnews.com/enginemaintenance/bingjet.html



Or



http://www.ultralightnews.ca/bing/index.html



And To sync the 912 carbs.



http://www.ultralightnews.ca/bing/912carbsync.html



Hope this helps.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

lcfitt(at)sbcglobal.net
Guest

Posted: Fri Dec 29, 2006 7:30 am Post subject: Possible overheating and EGT question

Torgeir,



I have understood, as you say, that the the EGT probe is measuring a 

differential temperature between the probe and the end of the metal shielded 

lead.  My lead does not terminate in the cockpit, although there is 

sufficient length to do so.  The leads on the Lancair IV I am helping with 

are too short to enter the cockpit  We coiled the leads aft of the first two 

cylinders so the leads terminate in the same relative location, but they are 

in the engine compartment.  These airplanes are built to fly in the flight 

levels so positioning the terminals above the baffling would give the 

reference temps a great fluctuation.  They are positioned below the baffles 

of necessity due to their length.



Your thoughts.



Lowell

---

Lynn Matteson

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

Posted: Fri Dec 29, 2006 7:55 am Post subject: Possible overheating and EGT question

Lowell-



I think what Torgeir said was that the EGT reading is a differential  

between the probe and the cockpit temp. My understanding of my EIS is  

that it references the unit temperature...that is, the temp of the  

EIS "unit" itself, and any other temp that you are monitoring. If  

Torgeir was not talking about the EIS unit, this comment may not apply.



Lynn

On Dec 29, 2006, at 10:29 AM, Lowell Fitt wrote:



[quote] 

 <lcfitt(at)sbcglobal.net>



 Torgeir,



 I have understood, as you say, that the the EGT probe is measuring  

 a differential temperature between the probe and the end of the  

 metal shielded lead.  My lead does not terminate in the cockpit,  

 although there is sufficient length to do so.  The leads on the  

 Lancair IV I am helping with are too short to enter the cockpit  We  

 coiled the leads aft of the first two cylinders so the leads  

 terminate in the same relative location, but they are in the engine  

 compartment.  These airplanes are built to fly in the flight levels  

 so positioning the terminals above the baffling would give the  

 reference temps a great fluctuation.  They are positioned below the  

 baffles of necessity due to their length.



 Your thoughts.



 Lowell

 ---

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

propellerdesign(at)tele2.
Guest

Posted: Fri Dec 29, 2006 9:28 am Post subject: Possible overheating and EGT question

What I understand is that the reading is between  the probe inside the exhaust tube, and the part of the wire closest to the  probe, that's why it work better if it get cold air flow over the  wires.

  

 Jan

 [quote]   ---

torgemor(at)online.no
Guest

Posted: Fri Dec 29, 2006 11:17 am Post subject: Possible overheating and EGT question

I was afraid about that you'll become confused.

Sorry for this.

Well, you was talking about over temp. due to the fact that some of the  

coolant escaped through the overflow, right.

You did not state engine type, but I'll guess it's a 912?

An unsynchronized carb. most often create vibration and rough running  

engine, due to different mixture between the two sides of the boxer engine.

This can sometimes be seen as a "big" difference in EGT reading between  

the cylinder pairs (L/R side pairs differing to much).

Your problem is prob. due to winter operation -but, and your engine might  

run lean, this increase the water temperature.

Or ?, this might be related to the cooling system itself, water pockets,  

water pump or sometimes just a little lo on the water level ??

Well, you've already got "manual" references, so wishing you good luck.

Torgeir.

On Fri, 29 Dec 2006 06:10:29 +0100, wingnut <wingnut(at)spamarrest.com> wrote:

 	  Quote: 	

> When I said one notch up, I meant one notch to bring the needle up  

> having

> more rich mixture.

>

> To actually do this, the locking ring has to go one notch down on the

> needle itself...

 OK. Now I'm really confused. You wouldn't happen to know where I can  

 find an illustration of what you are talking about? Also, when adjusting  

 the mixture at the carb, how does one ensure that the two carbs stay in  

 sync?

 -Luis

 -824KF

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=84145#84145

-- 

Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

torgemor(at)online.no
Guest

Posted: Fri Dec 29, 2006 11:17 am Post subject: Possible overheating and EGT question

You're correct Lowell, the cold junction is at the connection point of the  

thermocouple harness. This is the "harness" that's connected directly to  

the probe.



Normally, this two wires "Chromel and Alumel" is connected directly to the  

indicator, this is why "the cold junction point" normally is referred to  

the indicator location.



However, now an then wires need to be changed or modified for various  

reasons.  In your case, the thermocouple harness is to short. Normally we  

would order an extended thermocouple. Often we find them in three  

different lengths, but all of them has the same resistance, if you measure  

them with the EGT probe immersed into a mixture of ice and water. If this  

mixture is stirred, it's the lab. definition of zero degrees Celsius, the  

freezing point.  In fact folk, we're using this method to really calibrate  

accurate those big jet engines EGT systems, and here we're talking about a  

different of one tent of a degree!!



The connection method Westberg (or nowadays Westach) use is the so called  

"uncertain method", which is good enough for the kind of use they mention!



I've attached a little picture from their web site, that's show this  

method very well. Anyway, the cold junction temperature Westach use is 70  

Deg. F., or 21.11 Deg Celsius. This is their way of philosophy, cause most  

operation take place in this temperature area, so the end result "might"  

not be to far away if the cold junction is ignored.



The other calibration point they are using is the zero degrees Celsius  

reference, this is in fact the standard cold junction reference point, did  

you know that the "Chromel/Alumel" give 0 VDC at this temperature??   

Handy, isnâ€™t?



Now back to your problem, the short thermocouple harness.  Do you know the  

actual resistance for his cable(this value is often stamped on the  

instrument side)?



If those two wires is to be extended, you'll have to make sure that the  

total resistance do not increase to much, as this will create an  

additional error and the indicator will give to low reading when temp is  

high.



The standard cable (thermocouple) Westach are using is 2.4 Ohm. This total  

value is not to be altered as this will ruin the system accuracy. There is  

several solutions to this, the first and simplest is to use another probe  

option with extended leads.



There's two more methodâ€™s, "the preferred" Chromel/Alumel connection  

method -and a simple extension using "the preferred" connection.

Then to the link, Westach is here:



http://www.westach.com/



On the left side under INFORMATION, select Hardcopy Catalog then roll down  

and select page 53; Then you'll see (the original picture)"THE PRINCIPLE  

OF A THERMOCOUPLE"



So if you got one of those indicators, you'll find all the information  

needed here for all of their instruments -also connection sheets etc.



The important thing is the resistance in the "added wires"  -and that the  

two spliced wires is in the same "temperature environment" that you can  

measure all the time!



Remember, the temperature here (at the cold junction point) decide your  

corrected reading -your true EGT temp.

Later on I'll make a few drawings how we use to connect the cold junction  

by using the "preferred method". Maybe also a little about how we can  

manipulate the system and still have a correct reading.

Torgeir.





On Fri, 29 Dec 2006 16:29:49 +0100, Lowell Fitt <lcfitt(at)sbcglobal.net>  

wrote:



[quote] 



 Torgeir,



 I have understood, as you say, that the the EGT probe is measuring a  

 differential temperature between the probe and the end of the metal  

 shielded lead.  My lead does not terminate in the cockpit, although  

 there is sufficient length to do so.  The leads on the Lancair IV I am  

 helping with are too short to enter the cockpit  We coiled the leads aft  

 of the first two cylinders so the leads terminate in the same relative  

 location, but they are in the engine compartment.  These airplanes are  

 built to fly in the flight levels so positioning the terminals above the  

 baffling would give the reference temps a great fluctuation.  They are  

 positioned below the baffles of necessity due to their length.



 Your thoughts.



 Lowell

 ---

EGT.jpg

Description:

Filesize:

64.97 KB

Viewed:

395 Time(s)

torgemor(at)online.no
Guest

Posted: Fri Dec 29, 2006 12:23 pm Post subject: Possible overheating and EGT question

Hi Lynn,



Yes, you're right by now you've probably been reading my post to Lowell  

about this.



Funny that you mention the EIS, I'm a little curious about this system,  

cause such a modern design should have an automatic cold junction  

compensation system built in, I.E. the system measure the actual  

instrument temperature and then correct the reading so you'll always be  

reading the true EGT (well, -the temp at the probe).



If you are using this system, it could be interesting to know their cold  

junction reference.



Yes, the principle is just the same, except that they're using an  

amplifier and an analog to digital converter -vola..



Torgeir

On Fri, 29 Dec 2006 16:56:27 +0100, Lynn Matteson <lynnmatt(at)jps.net> wrote:



[quote] 



 Lowell-



 I think what Torgeir said was that the EGT reading is a differential  

 between the probe and the cockpit temp. My understanding of my EIS is  

 that it references the unit temperature...that is, the temp of the EIS  

 "unit" itself, and any other temp that you are monitoring. If Torgeir  

 was not talking about the EIS unit, this comment may not apply.



 Lynn

 On Dec 29, 2006, at 10:29 AM, Lowell Fitt wrote:



> 

>

> Torgeir,

>

> I have understood, as you say, that the the EGT probe is measuring a  

> differential temperature between the probe and the end of the metal  

> shielded lead.  My lead does not terminate in the cockpit, although  

> there is sufficient length to do so.  The leads on the Lancair IV I am  

> helping with are too short to enter the cockpit  We coiled the leads  

> aft of the first two cylinders so the leads terminate in the same  

> relative location, but they are in the engine compartment.  These  

> airplanes are built to fly in the flight levels so positioning the  

> terminals above the baffling would give the reference temps a great  

> fluctuation.  They are positioned below the baffles of necessity due to  

> their length.

>

> Your thoughts.

>

> Lowell

> ---

Lynn Matteson

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

Posted: Fri Dec 29, 2006 6:25 pm Post subject: Possible overheating and EGT question

I just looked for my manual for the EIS, but it's at the hangar. I  

know they mention the cold junction, and say that it should be kept  

as far from heat sources as possible, so they must be worried that  

this junction will get hot and foul up the reading. But elsewhere I  

recall reading that the unit temperature is what is used to compare  

all other temp readings to, so I'm at a loss to say anything,  

really...and I'm certainly no electronics person.



Lynn

On Dec 29, 2006, at 3:22 PM, Torgeir Mortensen wrote:



[quote] 

 <torgemor(at)online.no>



 Hi Lynn,



 Yes, you're right by now you've probably been reading my post to  

 Lowell about this.



 Funny that you mention the EIS, I'm a little curious about this  

 system, cause such a modern design should have an automatic cold  

 junction compensation system built in, I.E. the system measure the  

 actual instrument temperature and then correct the reading so  

 you'll always be reading the true EGT (well, -the temp at the probe).



 If you are using this system, it could be interesting to know their  

 cold junction reference.



 Yes, the principle is just the same, except that they're using an  

 amplifier and an analog to digital converter -vola..



 Torgeir

 On Fri, 29 Dec 2006 16:56:27 +0100, Lynn Matteson  

 <lynnmatt(at)jps.net> wrote:



> 

>

> Lowell-

>

> I think what Torgeir said was that the EGT reading is a  

> differential between the probe and the cockpit temp. My  

> understanding of my EIS is that it references the unit  

> temperature...that is, the temp of the EIS "unit" itself, and any  

> other temp that you are monitoring. If Torgeir was not talking  

> about the EIS unit, this comment may not apply.

>

> Lynn

> On Dec 29, 2006, at 10:29 AM, Lowell Fitt wrote:

>

>> 

>> <lcfitt(at)sbcglobal.net>

>>

>> Torgeir,

>>

>> I have understood, as you say, that the the EGT probe is  

>> measuring a differential temperature between the probe and the  

>> end of the metal shielded lead.  My lead does not terminate in  

>> the cockpit, although there is sufficient length to do so.  The  

>> leads on the Lancair IV I am helping with are too short to enter  

>> the cockpit  We coiled the leads aft of the first two cylinders  

>> so the leads terminate in the same relative location, but they  

>> are in the engine compartment.  These airplanes are built to fly  

>> in the flight levels so positioning the terminals above the  

>> baffling would give the reference temps a great fluctuation.   

>> They are positioned below the baffles of necessity due to their  

>> length.

>>

>> Your thoughts.

>>

>> Lowell

>> ---

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Dec 30, 2006 6:01 am Post subject: Possible overheating and EGT question

Enough to say Lynn your EIS is probably a darn sight more accurate than my

EGT.  As long as you didn't cut any wires or use speaker zip wire in your

installation.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Lynn Matteson

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

Posted: Sat Dec 30, 2006 6:48 am Post subject: Possible overheating and EGT question

Right on Noel, re the speaker wire...not even Monster wire would work  

here. : )  Actually though, the instructions say that you CAN cut the  

wires shorter:



"NOTE: The length of wire on the EGT & CHT probes, or the extension  

wire may be shortened as desired for your installation."



A personal note on their NOTE....I'm almost certain that I recall  

speaking to Sandy at Grand Rapids Technologies (EIS) about shortening  

the wires, and she said that you can shorten the wires coming from  

the unit...actually the connector... but NOT the probe wires.



Torgeir-

I just read the manual re the "unit temperature"...to quote:



"This function is displayed on the hourmeter page, and shows the  

internal temperature of the instrument. It is used by the instrument  

for cold-junction compensation of the EGTs and CHTs. It is also  

useful for estimating the cabin temperature, as it tends to stabilize  

at about 30-35 degrees F above the ambient temperature."



It goes on to mention that it (the unit temperature) can be used to  

check for excessive instrument (the EIS itself) heat, but that's not  

pertinent to this discussion.



Lynn



On Dec 30, 2006, at 9:00 AM, Noel Loveys wrote:



[quote] 



 Enough to say Lynn your EIS is probably a darn sight more accurate  

 than my

 EGT.  As long as you didn't cut any wires or use speaker zip wire  

 in your

 installation.



 Noel



> --

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Dec 30, 2006 7:51 am Post subject: Possible overheating and EGT question

The probe wires is what I was referring to not being cut. The probes are

usually available with several different length harnesses.  All of which

will have identical internal resistances.



As you wrote, your EIS  has a second probe built in, physically close to the

cold junction that monitors the temp of that junction and automatically

makes your compensation corrections for you. That's the best. Except of

course if you loose your EIS at which time you will have more worries than

an EGT a couple of degrees too high.



Some other instruments will have a little bi-metallic spring, similar to

what is found in a thermostat, in the meter that will make adjustments for

the temperature of the cold junction.  Sort of second best.  In the event of

a power out you won't lose your EGT but the bi-metallic spring can after a

time lose its calibration.



My EGT doesn't have any compensation built in but the documentation says it

is calibrated for 20C (68F) Since my cockpit temps seldom if ever get above

68F the instrument is usable.  Even if the cockpit temps went up to 80F the

accuracy of reading the meter because of parallax etc is probably close to

the 12F the meter will be reading too low.  



In flight my EGTs show an almost even 1100F my plugs say they are getting

good mixture so I can now depend  ( to an extent ) on my EGT gauge.  I will

probably continue to check my plugs every 5-10 hr.



I got into a discussion with a gentleman on another group last year about

the use of extending probe harness with copper speaker wire.  He said the

two extra junctions that were created would balance each other out and the

instrument would still be accurate.  Actually there would be four junctions

created as the connectors actually on the instrument are chromel and alumel.

He considered a few feet of copper wire to have a resistance of 0 so it

wouldn't throw off his EGT.  In fact the way he uses his EGTs just to follow

temperature trends it probably works for him.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Clem Nichols

Joined: 10 Jan 2006
Posts: 88
Location: Munfordville, Ky

Posted: Sat Dec 30, 2006 9:09 am Post subject: Possible overheating and EGT question

For whatever it's worth, there's an article on page 48 or the January 2007 

issue of  "Light Sport and Ultralight Flying" which covers this very 

subject.  It's written by Arnold C. Anderson who is now retired after 

spending "  I37 years in the engine and aerospace industry as a mechanical 

engineer, designing electro-mechanical equipment and solving reliability 

problems in equipment for unmanned deep space missions".  I would think that 

this issue could probably be purchased by going to www.ultralightflying.com.



Clem Nichols

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