V

Vlad

Well Known Member
If you had a choice of only one EGT sensor on four-cylinder Lycoming, which cylinder would you choose to install it on?
 
L.Adamson said:
And I only have the one CHT & EGT. Both on #3

L.Adamson --- RV6A
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point taken thank you.
I've read somewhere that single CHT and EGT were installed on different cylinders and there was an explanation why. I can not find the discussion.
 
Why? On multi probe setups this is true, but there are tons of airplanes that aren't setup that way on single probe.
 
pyrometer what?

I think it has to do with the little blue flame that likes to hide behind the exaust valve and only comes out very fast and if you have a good sociometric mix only a short distance into the pipy thingy. That way you can get a good pyrometer read on the top of his head. Listen to Mel on this one, hes been there done that..
Yours as always REA III #80888
 
Thank you guys for your answers. I was looking for opinion not where to attach single EGT probe on the exhaust pipe but what cylinder could be the best indicator for leaning purposes. Larry mentioned that he has both EGT and CHT on #3. I have read a lengthy discussion a while ago where somebody gave a good explanation why single EGT could be installed on cylinder other than #3. My third will have CHT (single) probe.
 
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I think the issue is that if you are running a single probe egt, you want to get it on the leanest cylinder. That may vary from installation to installation. You will not know if you got it on the leanest cylinder until you can fly the aircraft and lean the engine. A lot of times the leanest cylinder is number three so that might be a good place to start. If that decision turns out wrong you need to move the probe to another cylinder until you find the leanest cylinder. When you lean to the leanest cylinder, you will not get different leaning characteristics then if you were using a multi probe setup.... only more information. So, your fuel burn should be the same, leaned to the leanest cylinder and only sensing that cylinder or leaning to the leanest cylinder and being able to see what the others are doing.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
osxuser said:
If I had only one, I'd put it into my 4 into 1 collector...
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If you put the EGT probe into your 4 in one do you have to add them all up and divide by 4? :eek:


;)

Seriously, the collector would be way to far away from the valves. Like Mel said, the temps should be measured about 2" from the flange.
 
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mahlon_r said:
I think the issue is that if you are running a single probe egt, you want to get it on the leanest cylinder. That may vary from installation to installation. You will not know if you got it on the leanest cylinder until you can fly the aircraft and lean the engine. A lot of times the leanest cylinder is number three so that might be a good place to start. If that decision turns out wrong you need to move the probe to another cylinder until you find the leanest cylinder. When you lean to the leanest cylinder, you will not get different leaning characteristics then if you were using a multi probe setup.... only more information. So, your fuel burn should be the same, leaned to the leanest cylinder and only sensing that cylinder or leaning to the leanest cylinder and being able to see what the others are doing.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
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Thank you Sir,
The leanest one it will be.
 
Vladyspassky said:
Thank you Sir,
The leanest one it will be.
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But...................how will you know what's the leanest one? Drill holes in all four exhaust pipes, and keep remounting the probe? I settled on #3, because it's usually the leanest, from what I'd heard, but not always. If I was doing it again, I'd have a multi-probe setup; but I'm a cheapskate these days..

L.Adamson --- RV6A
 
Mahlon gave pretty good explanation. I will start with #3 because it is usually the leanest. Hey and I can compete with you on the cheapskate one... like totally removing the gage if it doesn't help;)
 
Vladyspassky said:
If you had a choice of only one EGT sensor on four-cylinder Lycoming, which cylinder would you choose to install it on?
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A boat, or something else less sensitive to causing death if it fails. Then I'd buy and install a real 4-sensor package on my airplane.

:D
 
breister said:
A boat, or something else less sensitive to causing death if it fails. Then I'd buy and install a real 4-sensor package on my airplane.
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There are a whole lot of certified planes out there with just one cht and egt, if even that. They don't all seem to be falling out of the sky...

L.Adamson
 
I also have only one EGT and it is on #3, it's on #3 cylinder for no particularly good reason. Here is a link a Lycoming Service Instruction note that addresses engine leaning on page 3.

http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1094D.pdf

My RV7 is carburated with a fixed pitch prop and I've been applying the methods descripted in the article. Maybe with an injected engine it would be more important to monitor the EGT of all 4 cylinders but with a carburated engine, the EGT's are what they are, and you don't really care which cylinder leans first, only that the engine is over lean. The pilot can easily hear an overleaned engine and quickly correct it. The EGT guage just confirms what the pilot already heard.
 
L.Adamson said:
There are a whole lot of certified planes out there with just one cht and egt, if even that. They don't all seem to be falling out of the sky...

L.Adamson
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Soooo true. When we did put the JPI on our C177 and found out the CHT's were hitting 450-480+ on a regular basis we almost died... :/
 
L.Adamson said:
There are a whole lot of certified planes out there with just one cht and egt, if even that. They don't all seem to be falling out of the sky...
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And those manufacturers likely conducted flight testing with four EGTs and four CHTs, so they could see which cylinder was critical. Then, on production aircraft, they only installed EGT and CHT on the critical cylinder.

The kicker is that the critical cylinder depends on the details of the installation. The exhaust system design, oil sump part number, cylinder baffling, etc could affect mixture distribution or cylinder cooling.

Given the cost of the engine, it seems to make sense to invest a bit more on engine instrumentation, rather than risk expensive cylinders to the effect of undetected overheating.
 
Kevin Horton said:
And those manufacturers likely conducted flight testing with four EGTs and four CHTs, so they could see which cylinder was critical. Then, on production aircraft, they only installed EGT and CHT on the critical cylinder.
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And that's how we came up with cylinder #3 in my case. Lot's of 6's were out flying before mine. I'm not going to argue about the instrumentation though. I like the new digital "stuff". My panel goes back to the six pac days.

But regardless, after many years of high altitude leaning with aircraft that didn't even have EGT, and the fact that I have a carb and don't lean LOP, I might just survive.

L.Adamson
 
L.Adamson said:
There are a whole lot of certified planes out there with just one cht and egt, if even that. They don't all seem to be falling out of the sky...

L.Adamson
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That's why the smiley face - it was tongue in cheek.

Still, for my personal preferences and desiring as I do to regularly fly LOP, I don't feel that a single-sensor setup would be satisfactory to me personally.
 
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