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Possible overheating and EGT question
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Fox5flyer
Guest

Posted: Sat Dec 30, 2006 9:50 am Post subject: Possible overheating and EGT question

The ambient cockpit temp may very well be at 68f, but I wouldn't bet on what

it is under that panel.  It depends on a lot of things, some of which are

the radios, transponder, various other heat producing electronics, heater

fluid lines and the heater core itself (if there is one), amount of heat

producing sunlight hitting the (usually) dark glare shield, heat being

transmitted by the firewall, etc.  My EIS has an internal temp reading that

is often over 120f on hot flying days.  Well, hot for up here in NE Michigan

anyway.  I imagine it would be considerably higher down in the desert

climates.  Of course, this is all relative to the amount of ventilation that

is provided for the electronics and I suspect that many of us have very

little to nothing.  Hopefully my EIS compensates for that temp difference,

but if it really does, I don't know.  Has anybody stuck a thermocouple up

under the panel to see what their temp is?  I've always planned on running a

vent tube up there, but I just haven't been able to get to it.

Regards,

Deke

S5



snip...

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

it
	


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

above
	


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

the
	


 	  Quote: 	
		   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
	


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

..snip

Float Flyr

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

Posted: Sat Dec 30, 2006 12:13 pm Post subject: Possible overheating and EGT question

All valid points Deke:



The only thing I have in my panel that can generate any heat is the T&B.  I

tend to use my EGT mostly as a trend indicator and If I tell you my EGT was

1100F then there is an error Could be as much as 50F either way in that

reading.  In the mean time I'm not too worried because there is enough air

leaks and draughts in the cockpit to fly a kite ( if I had more room).  I

fold my wings after every flight and usually do a pretty good post flight

inspection so sealing the areas of air leaks isn't high priority for me.  If

I put the skis on this winter I'll just wear my WW II Flight pants and a

good heavy parka.



The documentation on your EIS should give you the operational temperature

range.  I think the high end will probably be around 150F (65C).  After that

thermal runaway of electronic components is a possibility.  You will get an

indication of that when your EIS just stops.  Seriously though there is

probably an indicator on your EIS to let you know when its too hot.



My mother always said, "When all else fails.... Read the instructions".



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

torgemor(at)online.no
Guest

Posted: Sat Dec 30, 2006 12:39 pm Post subject: Possible overheating and EGT question

Hi Lynn,



ok., then your instrument do compensate for "cold junction", good -seems  

to be an excellent unit!



Those "new" instruments use "high impedance" amplifiers in the first  

stage, therefore they do not load the "thermo couple" that much, the patch  

cable may then be quite long, -even long enough for a Kitfox.  

Interesting.



Cheers

Torgeir.

On Sat, 30 Dec 2006 15:49:15 +0100, Lynn Matteson <lynnmatt(at)jps.net> wrote:



[quote] 



 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:



> 

>

> 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 Matteson

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

Posted: Sat Dec 30, 2006 1:29 pm Post subject: Possible overheating and EGT question

Quote from the (mine anyway) manual:

"Unit temperatures above 170 degrees F can degrade the readability of  

the display. (The display will return to normal when it is cooled to  

normal temperatures.) Temperatures above 200 deg F can activate the  

internal thermal fuse, shutting down the instrument."



Lynn

On Dec 30, 2006, at 3:13 PM, Noel Loveys wrote:



[quote] 



 All valid points Deke:



 The only thing I have in my panel that can generate any heat is the  

 T&B.  I

 tend to use my EGT mostly as a trend indicator and If I tell you my  

 EGT was

 1100F then there is an error Could be as much as 50F either way in  

 that

 reading.  In the mean time I'm not too worried because there is  

 enough air

 leaks and draughts in the cockpit to fly a kite ( if I had more  

 room).  I

 fold my wings after every flight and usually do a pretty good post  

 flight

 inspection so sealing the areas of air leaks isn't high priority  

 for me.  If

 I put the skis on this winter I'll just wear my WW II Flight pants  

 and a

 good heavy parka.



 The documentation on your EIS should give you the operational  

 temperature

 range.  I think the high end will probably be around 150F (65C).   

 After that

 thermal runaway of electronic components is a possibility.  You  

 will get an

 indication of that when your EIS just stops.  Seriously though  

 there is

 probably an indicator on your EIS to let you know when its too hot.



 My mother always said, "When all else fails.... Read the  

 instructions".



 Noel



> --

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Lynn Matteson

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

Posted: Sat Dec 30, 2006 1:35 pm Post subject: Possible overheating and EGT question

Thanks for that summation, Torgeir. I'm no electronics guru...I don't  

even play one on TV : )...so that vote of confidence in the EIS is  

welcome news.



Lynn

p.s. Yes, the leads are quite long...mine are still coiled up behind  

the panel...just in case. One of these days I'll shorten them up for  

neatness' sake.



On Dec 30, 2006, at 3:39 PM, Torgeir Mortensen wrote:



 	  Quote: 	
		   

 <torgemor(at)online.no>

 Hi Lynn,



 ok., then your instrument do compensate for "cold junction", good - 

 seems to be an excellent unit!



 Those "new" instruments use "high impedance" amplifiers in the  

 first stage, therefore they do not load the "thermo couple" that  

 much, the patch cable may then be quite long, -even long enough for  

 a Kitfox.  

 Interesting.



 Cheers

 Torgeir.

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

torgemor(at)online.no
Guest

Posted: Sat Dec 30, 2006 2:01 pm Post subject: Possible overheating and EGT question

Lowell and All,



here's the next one about the EGT; this time about the thermocouple  

connection methods, just the three of them.



In the end of this you'll find the visual wives of cold junction, the way  

I often use to explain it.



This first one, is our standard Westach setup, a straight through setup  

accepting some error.

The second one is the preferred connection setup of a thermocouple, this  

one has no error if it is correctly corrected for cold junction  

temperature and the instrument has no error!

The last one is a combination of the above, but also manipulating the  

thermocouple resistance in order to extend the distance between probe and  

indicator.

All of these drawings is made (yesterday night) with AutoCAD, the files is  

converted to jpg for the ease of presentation. (They might look a little  

“gray”, but this is due to the high compression.)

Next time we'll see how "cheap devices" can be used to measure cold  

junction temperature and OAT.



(Prob. Next year.)

Torgeir.

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Float Flyr

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

Posted: Sat Dec 30, 2006 2:44 pm Post subject: Possible overheating and EGT question

That's normal for LCD displays.  If you leave your GPS out in open sunlight

too long it will go all black and you won't be able to read anything on it.

After it cools even slightly the display returns to operational condition.



The 200 (F) thermal fuse is the upper end of the EIS operation ( the 'puter

that runs the display) if it gets that hot under your instrument panel (if

that's where your EIS unit is) believe me you're cooked or at least par

boiled.



The EIS unit Gathers info from your engine then drives your display...

There is no holy book that says it needs to be close to the display.  I

would guess harnesses can be made for the digital display of any necessary

length.



I would love to have your system set up for the 582.  Two strokes are

particular about EGT.  Mixture can be changed by either applying or reducing

throttle and/or load.



Now I'll dream about a full FADEC two stroke fuel injection.... Hmmmm sounds

like the engine Rotax cancelled last spring.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

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

Posted: Sat Dec 30, 2006 4:05 pm Post subject: Possible overheating and EGT question

I don't have CAD on this computer.  My copy is 2000 and won't load onto the

XP.  S I did this up on Photoshop.



It is a Rough, and I mean rough, diagram of my EGT schematic as came with my

EGT documentation... I don't intend to open the Instrument to check on the

location of the cold junction 

 

Just one more configuration.



Still prefer the EIS set up Lynn has... Just need one for 2 cyc.



Cheers and Happy New Year

Noel



[quote] --

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

kenharrison(at)ubgcharlot
Guest

Posted: Sun Dec 31, 2006 9:28 am Post subject: Possible overheating and EGT question

Hello all,  

  I have a quick question on this topic of EIS/EGTs.  I have searched the archives but don’t see any info. I have an EIS which I was going to use for EGT, CHT, Water temp.  Has anyone considered using a regular “steam guage” EGT instrument in conjunction with the EIS, as a backup.  Can such a thing be done on the same EGT probe?    

   

  I have a panel that has all the “steam gauges”, and would like to add the EIS as a backup to all of them if that’s possible.  Has anybody ever done this?  

   

Thanks for the help,  

Ken  

        [quote][b]

Float Flyr

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

Posted: Sun Dec 31, 2006 12:21 pm Post subject: Possible overheating and EGT question

The "steam gauge" should be  wired in parallel with the EIS using chromel(+) and alumel(-) wires. those  wire can be hard to get.  Some say it's ok to use copper wires but that  introduces more junctions as well as resistances. 

  

 The problem is the resistance  across the "steam gauge" is not nearly as high as the close to infinite  resistance across the input terminals of your EIS.  Therefore it is  possible the introduction of a mechanical gauge will disrupt the calibration of  your EIS.  It could lower the voltage across both EGT and EIS inputs.   

  

 Another problem is your EIS  probably has a cold junction built in to it which has the temperature  consistently monitored.  If Your steam gauge has a cold junction built in  (it probably does) then that junction should be removed.  That means  opening the mechanical gauge head, removing the cold junction and resealing the  gauge.

  

 Go with the EIS alone on this  one...  If it goes blank you will have more to worry about than an EGT  arbitrarily sky rocketing.  There are some instruments that having a second  back up set of gauges is nice to have e.g. tachometer and fuel quantity. but one  of the reasons to install an EIS is to save weight so installing both won't help  matters.

  

  

 

Noel [quote]   

   --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

czkree(at)netzero.net
Guest

Posted: Mon Jan 01, 2007 12:23 pm Post subject: Possible overheating and EGT question

You had talked about your egt's at take off being high or close to the max

limit. At take off I will assume you are at full throttle? At the full

throttle setting you are no longer using the needle, you would be using the

main jet. If the temps are high changing the needle will not do much for you

at full throttle. You will need to go in and change the main jet to the next

larger size. The needle is only going to affect your mid range. You ask if

it is normal to change carb settings? Sure it is as the density of the air

changes so does the mixture. More dense the air the leaner the mixture, less

dense air, richer mixture, if you do nothing. This is the most common time

to make the lean to rich change. In the spring it would be rich back to

lean.



As Rex stated you will not change the sync. if you do the same change to

both carbs.



Steve

STA-Lite Aviation, Inc.

Authorized Rotax Repair Station

www.staliteaviation.com



---

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