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EGT probe installation problem: oversize holes

kaa

Well Known Member
Hi all,

I'm upgrading to a Garmin panel and hit a snag with the EGT probes. The probes supplied with Garmin equipment call for #31 hole, and the old probes I have were installed in a 3/16 hole. I'm fairly certain that if I just install the new probes into existing holes they'll leak. So now I'm trying to figure out what to do. One option is to remove the exhaust and send it somewhere to be welded up, but that seems like a hassle. Is there anything else I could do if I don't want to relocate the probes?

Appreciate any ideas.

Thanks!
 
Thanks, missed that thread.

I'm not trying to relocate the probes though, and I worry that if I reuse existing holes, the new Alcor probes will leak.
 
A few thoughts before removing the complete exhaust system, if you have access to a Lathe, turning up a few bushing from Stainless would solve the fit problem. If not , a 3/16? Stainless Steel pulled rivet with the mandrel pushed out will be close to ID needed for the probe.
 
I am still using the original 'R' EI probes that came with the EI kit, over 1700 hrs on them.

From ACS website:

P-110-R EGT/TIT Standard 13/64" dia Probe (Robust).

"The basic difference between the P-110R (robust) and the P-110F (fast response) is the physical diameter of the probe. The P-110F measures .125" and the P-110R measures .187".
 
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Thanks everyone for suggestions, I appreciate the help!

I was thinking about drilling out a flat head screw, but a blind rivet might work even better. I also found these vented screws at McMaster, which may be easier to drill through: https://www.mcmaster.com/90550a610, so I'll try these too. Sadly I don't have access to a lathe.
 
Konstantin,

Check to see if the manufacturer of your instrument sells a probe that will fit into the EGT hole in your pipe.

There are three things you don't want to change in order to get an accurate reading. 1)The depth the probe sticks into the exhaust path. 2) The distance from the exhaust port 3) the length of the wire from the probe to the connector.

If you change any of these you're wasting your time and should just save the money and not install the EGT.

I'm sure, welding a bung onto your exhaust which is probably made of inconel or monel won't be expensive, but finding someone who knows what they're actually doing and not just some hack will be the most difficult part.
 
There are three things you don't want to change in order to get an accurate reading. 1)The depth the probe sticks into the exhaust path. 2) The distance from the exhaust port 3) the length of the wire from the probe to the connector.

If you change any of these you're wasting your time and should just save the money and not install the EGT.

If you're trying to get the values to match from pipe to pipe, yeah...same distance, same depth, same wire length. But you say "change" in reference to "accurate" readings.

The probes will be accurate wherever you put them, per their spec (usually something like +- 2% within a certain temp range).

And for EGT, it doesn't really matter where you put them, etc., anyway...you really only care about finding PEAK EGT, and then referencing that either side for ROP or LOP ops.

IOW, there's no defined position, depth, or wire length that is any more accurate than any other one, to begin with.

Unless I don't understand what you're saying here about "accuracy"... ? I dunno...
 
I have a hard time imagining that moving a thermocouple a few millimeters out of the exhaust pipe will have a significant effect, given how EGTs are used. Plus these thermocouples accommodate different pipe diameters.

Also, why does the length of the wire matter? I have never heard about it, and it is my understanding that as long as there are no dissimilar metal connections between the thermocouple and and the engine monitor, the length of the run doesn't matter.
 
Ever notice the probe comes pre connected, but you need to put the connector on the wire from the EIS?
 
Yes, but where does the length come into play? I don't understand the physics of the situation. Plus, if a splice connector like OLC-2 is used, then no dissimilar metal joint is ever formed, so it should behave as a single wire.
 
The rivet idea worked pretty well. I got a 3/16 stainless steel rivet from McMaster and cut the flared bit off. It fits pretty well, so I hope it'll seal ok.

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