Air Vents and EGT wiring

Time: 5 hours

I purchase a pair of 2″ AIrKit anodized aluminum vents from Aircraft Spruce. These things aren’t cheap, they’re around $160 each, but seem to be well made and are a good size for what I need to do. I also have AitKit cabin lights so everything kind of looks similar. I made up some fillers out of anodized aluminum (for the front)  and fiber glass sheet (for the back) with a 3 1/8″ hole saw. I then cut a 2″ hole in the middle using another hole saw. The cuts came out well enough. I had to modify the fiber glass ring a bit to get it to sit a bit flatter. The thread on the vents seemed to be long enough, but it was a pain getting the back to screw on. I epoxied the fiber glass ring to the rear of the dash and the front is just held in place by the pressure of the backing nut. I’m happy with the way these came out. They look a lot nicer then the plastic vents and they will seal off much better as well.

I also finally was able to finish up the wiring of the 2 EGT sensors. I had order some K Type  thermo coupler wire which appeared to be exactly what I needed at a reasonable price, but after running the wire and starting to wire it up I found that they had sent the incorrect wire (knew it was too good to be true). They said they will send the correct wire, but it’s back ordered (of course) and they weren’t sure when it would ship out. I decided to go back to my original place called Omega to purchase the wire. Their wire is really high quality but it’s pretty expensive. I purchase 25ft of armored K-Type thermo coupler wire for around $80. It arrived a few days ago and wow, it’s nice stuff. The wire I used (GG-K-20S-SB-25) is a 20 gauge glass insulated 2 core wire with an other glass insulator and then a stainless steel outer sheath. There are other sheathing you can get, but I wanted to use the braided stainless steel. The connection to the EGTs is made by 2 ring connectors, Unfortunately I could only find spade type connectors that are usable with the K-type wire. The spade connectors are made from Alumel and Chromel which is the same material as the K-type wire so the temperature characteristics will be the same. The yellow wire is Chromel so you use the Chromel spade connector on it and the red wire is Alumel so the Alumel connector is used on that. I used a standard open barrel crimper to crimp them on. Working with the K-type wire is a bit of a pain because the wire insulation is like a cloth material and doesn’t cut well with wire stripers. After the wires are bolted together a final length of heat shrink is put over it.

Lastly I roughed in the CEET tubing for the air vents. Because I’m using 2″ air vents I had to find a 3″ to 2″ reducer to tie into the NACA duct. I found some on Amazon for around $6 each and they look like they will work. The NACA duct is a little smaller than 3″ so hopefully it will seal up OK. I’m waiting on my hose brackets to be able to actually connect everything together. The one issue I ran into is that the bar that I’m going to install to hold the avionics shelf gets in the way of the tubing run.

Finer glass backing rung epoxied in.

Vent mounted in the 3 1/8″ anodized aluminum ring. It’s all just held in place with the pressure of the backing nut. The vent moves fairly easy so I don’t think it will be an issue with it coming loose. The fiberglass ring also creates some tension on the nut so it holds very tight and won’t spin loose at all.

EGT wire connection. I could only find spade connectors in Alumel and Chromel, but this all get wrapped in heat shrink so that will keep everything together and offer some strain relief.

Big piece of heat shrink covers up the join.

This 3″ to 2″ reducer looks like it will work. I may cut down the flange a bit to give more room. I need to use 3″ CEET to join it to the NACA duct and then 2″ out to the air vent.

Test fit of the CEET tubing for the air vents.The tight bend may cut down on air flow, but not much I can do about it. I don’t want to put the bar on the other side of the tubing because it may interfere with the fuel selector.

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