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Knisley exhaust egt location

silflexer

Registered User
I am installing a knisley dual exhaust on a 53 180. The slip joints in the middle cylinders force a move of the egt probes to about 4” from the manifold when the install recommends 1.5”. Anyone have experience with this? I can’t imagine it matters much as long as they are all at the same place.

thank you
 
I have the same exhaust and never got around to installing my EI 6 cylinder monitor. They way I understand it, you can drill a hole where it is supposed to be but since you don't want any shearing action, drill the hole bigger on the inside tube of the slip joint. That would require removing so you can get at it.
 
I have the same exhaust and never got around to installing my EI 6 cylinder monitor. They way I understand it, you can drill a hole where it is supposed to be but since you don't want any shearing action, drill the hole bigger on the inside tube of the slip joint. That would require removing so you can get at it.

I think that may be true but the instructions specifically state that the probe life will be greatly shortened and to avoid the slip joints. I don’t think that the change in location should really be that big of a deal just hoping someone else had experience with it.


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They way I understand it, you can drill a hole where it is supposed to be but since you don't want any shearing action, drill the hole bigger on the inside tube of the slip joint. That would require removing so you can get at it.

sounds lake an absolutely legit solution to me...
 
silflexer, one of my I.A.'s encountered this on a customer plane not too long ago. It was keeping the slip joint from doing its job. Same I.A. was just helping another friend interpret new CHT/EGT installation. I'll be working with him Sunday, will try to remember to ping him on the topic. Remember, EGT is a relative number: Distance from the exhaust port (not necessarily the bottom of the stack flange) should be consistent on all cylinders, but the absolute dimension is probably less important. The E.I. help desk is usually very good on these types of issues, too.

Glad to here your project is coming together.

Thanks. cubscout
 
All installation instructions I've used tell you a range that the probes SHOULD be installed at. But they also tell you that it is more important to keep them all the same distance from the flange. What brand and model of EGT system? I bet the install instructions warn against putting probes in a slip joint.

Web
 
Alcor and JPI say probe location 2”-4” from the flange. EI says 1-1/2” BUT
IMPORTANT NOTE: For Cessna 210’s or any aircraft using a slip joint in the exhaust system, install the EGT probes ABOVE or BELOW THE SLIP JOINT. Installing a EGT probe in the slip joint can damage the probe.
 
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Hi si,

As you know, our engine / airframe / exhaust install was the same as yours.

While I am far from an expert, it seemed to me that the manufacturer suggested location was just that, a good suggestion / starting point. there is no way this number could be a 'one size fits all'. I mean the differences in engine and exhaust size, shape, configuration, etc, let alone potential cowling differences could vary what a probe is seeing easily as much as the inch further your going to have to locate that probe. Does a C65 put it in the same place as an R-1820? Or an open cowled Ag-Cat the same as a Lancair? I honestly don't know, but those are the questions that ran through my mind as I walked through this.

Since IMHO the EGT is a relative number to begin with, I valued quality installation first, equal distancing next, and either over the manufacturer's suggested location. I put them just outside of the slip joint. The one inch difference may have shown a slight reduction in temps (I highly doubt it) but it allowed for a better install. I believe that as long as those numbers fall within a range acceptable for a recip to be running at, you will be able to use them appropriately, and it would matter not if they say 1405 vs 1395.

I also believe that having them equal distance will lessen your work load in deciphering information such as which one peaks first or which one is colder, hotter, etc...
All of this information would still be available with probes scattered in a six inch range, you would just have to struggle with looking at each individual depiction and then processing that information against the others.

My opinion is worth about what you paid for it, but I haven't replaced a probe in the 10 years it's been set up this way, the information has been invaluable, and it has alerted me to issues on more than one occasion. I would not pony up for a $50K + engine without something like this to help you get as much life as you can out of it.

Take care, Rob
 
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I have had my uninstalled EI for at least 15 yrs and know I read the slip joint procedure somewhere quite awhile ago. I'm not smart enough to think that one up. Could it be the install directions have been changed because it is a hassle to remove the exhaust to drill two bigger holes??????
 
No, it's because, inevitably, the holes will shift under heat and pressure and guillotine the probes.

Web
 
I doubt any instrument manufacturer will tell you to compromise the integrity of an exhaust joint. If Alcor says 2-4" I'd go with that since pretty much all the instrument manufacturers use Alcor probes.
 
Stewart, I hadn’t thought of looking up the alcor install instructions and was only referring to the EI instructions. Here is what the STC install manual says according to alcor “The probe should be located a minimum of 2 inches from the cylinder exhaust port flange (5 inches for highly supercharged engines) in an area free from weld beads or pipe irregularities.”

This is different than the 1.5” or clear of slip joints from EI. Case closed, thank you


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This is a clip from the CGR 30P manual. The stand alone EGT gauges are identical. These instructions tell you to determine the best location at which ALL probes can be mounted the same distance fron the exhaust flange. Yes it says 1 1/2", but that distance is called out as ideal, not mandatory. Now read the line titled 'Important Note:' It specifically says to install the probes either above or below a slip joint.

If you have an E.I. system use E.I instructions.

Web
 

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This is a clip from the CGR 30P manual. The stand alone EGT gauges are identical. These instructions tell you to determine the best location at which ALL probes can be mounted the same distance fron the exhaust flange. Yes it says 1 1/2", but that distance is called out as ideal, not mandatory. Now read the line titled 'Important Note:' It specifically says to install the probes either above or below a slip joint.

If you have an E.I. system use E.I instructions.

Web

That is the quote from the manual I put in my second post here thus my quest looking for folks that have experience with this to see if there have been any adverse operations after moving them lower.


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... thus my quest looking for folks that have experience with this to see if there have been any adverse operations after moving them lower.
The important part of a multi cylinder probe installation is that they all be the same distance from the cylinder exhaust flange. Too close reduces the lifespan of the probes. Too far away reduces the response times and sensitivity. Take a look where Cessna installed a single probe. Right next to the intake of the muffler after the three into one cluster joint. This provides an average of the three cylinders.
Remember the actual number of degrees is not important as you are only interested in whether the temperature is going up or down as well as it's relationship to the other cylinders. That's why Alcor doesn't have any numbers on it's instruments.
 
All installation instructions I've used tell you a range that the probes SHOULD be installed at. But they also tell you that it is more important to keep them all the same distance from the flange. What brand and model of EGT system? I bet the install instructions warn against putting probes in a slip joint.

Web
^^^ This. I have the Knisely dual exhaust on my '58 and also a 6 probe Insight GEM. I don't recall any issues installing them.
 
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