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egt probe, wrong location how bad

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occom

Joined: 26 Aug 2006
Posts: 404

Posted: Mon Aug 03, 2009 12:27 pm Post subject: egt probe, wrong location how bad

My 582 operating for about 300 hours has the EGT  probe mounted into the manifold about 1/2" from the exhaust flange. I know this  will result in an incorrect reading, but how much will it be off?  

   [quote][b]

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Aug 03, 2009 2:20 pm Post subject: Re: egt probe, wrong location how bad

If it is too close it will read hotter, too far and it will be cooler. Cap or plug the other hole and just re-drill at the proper distance. I don't know if there is a way to tell how many degrees you might be off. Most likely not a lot, but they do have a reason for the correct distance.



p.s.

I forgot to add that it can damage the probe sooner than it should. That's too close for the probe tip.

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Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
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Cell 520-349-7056

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Wed Aug 05, 2009 8:21 pm Post subject: Re: egt probe, wrong location how bad

Actually, the reverse is true.  A probe that's closer to the piston skirt will read lower.  I believe the analogy is something like a welder's flame where the hottest part is at the tip of the embedded blue flame further from the tip of the torch.



I've got this same problem on my 582 and would like to make sure my egt probes are exactly the right distance out on the manifold.  There are all kinds of complex methods for determining this for those of us who don't have the pre-drilled manifolds.  Instead, the easiest thing would be if someone with one of the factory drilled parts would just measure the distance from the edge of the exhaust flange where it mates to the manifold with the engine upright (spark plugs up) and publish it here.



Anyone?

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Thu Aug 06, 2009 3:49 am Post subject: egt probe, wrong location how bad

There's this one. If it's off it won't be by much.

http://www.ultralightnews.ca/exhaustsystems/egt_probelocation.htm



---

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Thu Aug 06, 2009 7:13 am Post subject: egt probe, wrong location how bad

I'm resisting the tempation to buy a new manifold and start over. In the

cleanup prior to begging a welding shop to close up the holes I noticed that

there actually were holes in approx the right place that have been welded

over in order to put the holes in the wrong place. Here is where the guy put 

them, little too close.

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bob(at)fly-ul.com
Guest

Posted: Thu Aug 06, 2009 8:28 am Post subject: egt probe, wrong location how bad

On 08:02 AM 8/6/2009, Dave G wrote:

 	  Quote: 	
		  Here is where the guy put them, little too close.


	


WAYY too close. As I recall, the Westach probes were supposed to be something like 2 1/8 inches away. I can't remember the exact distance, but for some reason 2 1/8 sticks in my mind. It was clearly closer to the mid point between the "Y" and the piston end of the manifold.



--

Bob Comperini

e-mail: bob(at)fly-ul.com

WWW: http://www.fly-ul.com

jay(at)horriblehyde.com
Guest

Posted: Thu Aug 06, 2009 8:43 am Post subject: egt probe, wrong location how bad

To me it doesn't matter particularly where the holes are- these do look a

bit close though!  Nonetheless, the important thing is to establish a trend.

Your actual temperatures may be off but the important thing is to note what

they are for YOUR engine- they seem to differ from installation to

installation in any case.  If you know what they are normally in different

attitudes and speeds then you will be using those temps properly.  When they

start to change then you know that something is wrong.



I had an engine failure 30 hours into a brand new engine (a manufacturing

fault) and I saw it coming because I was watching my temperatures.  The

water temperature was looking higher than usual, but I thought that was

because I had moved my ballistic parachute.  Then I noticed that the EGTs

were getting a bit higher than normal, and then their readings started

drifting apart- one cylinder getting hotter than the other.  When this

started I was 6 feet high over a marsh.  As soon as I saw the temps changing

I climbed and headed back towards my airfield.  Just as I got near to the

field, on a sort of base leg, the engine died.  Luckily I had height so it

was a simple dead stick landing.



An alternative my be to drill another set of holes, weld the threaded

inserts into both hole sets and then screw cap screws into the too close

ones and wire them shut.



Jay



--

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Aug 06, 2009 12:48 pm Post subject: Re: egt probe, wrong location how bad

The correct placement is 100mm or 4 in. from the rear of the piston. Drill the holes in the center of the exhaust tube. You can just plug your old holes up. You can tap and put screws in the holes, but they must be safety wired. Too close or too far will give an in-accurate reading and although you will see a trend you won't really know what the engine is doing. The better and more accurate readings you have the better you can run and tune the engine and know when things are not right before it is too late.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Thu Aug 06, 2009 1:12 pm Post subject: egt probe, wrong location how bad

Holes are plugged and redrilled in the proper location, ~100mm and the 

manifold is painted andback in place. I do wonder what reason the old owner 

had for changing the location. Never know I guess.

---

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Fri Aug 07, 2009 11:51 am Post subject: Re: egt probe, wrong location how bad

Number one reason Rotax engines have issues.....owners.

If everyone stuck to exactly what Rotax wanted we would have less issues, but experimentals experiment. I don't think it's always a bad thing so long as you have a good reason for doing it with full knowledge of the consequences down the road. I can't say I haven't experimented and taken my lumps, but that was many years ago. Now I leave the engine alone and experiment on non damaging ideas.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun Aug 09, 2009 2:47 pm Post subject: Re: egt probe, wrong location how bad

 	  Roger Lee wrote: 	
		  Number one reason Rotax engines have issues.....owners.

If everyone stuck to exactly what Rotax wanted we would have less issues, but experimentals experiment. I don't think it's always a bad thing so long as you have a good reason for doing it with full knowledge of the consequences down the road. I can't say I haven't experimented and taken my lumps, but that was many years ago. Now I leave the engine alone and experiment on non damaging ideas. 	


Well Said Roger. 



1 5/8" from cylinder port casting on a Kitfox with inverted Y  pipe ( not to mention a hacked one that costs Kitfox 582 driver about  5 to 7  HP .   I run the hacked Y pipe and a tuned pipe.   Yeah baby and  it works great with less fuel burn.  Over 400 hours testing on this pipe alone and on ethanol gas.   Woof !! 



I just went out to shop and looked at several  clamp style EGTs   one on my  582 and it about the same as a 532 Kitfox as well.

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EGT probe placement Ontario Rotax Parts , Service . www.cfisher.com

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EGT from the inside

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