12 channel EGT/CHT install

[gordner]

Last year I removed the CIS system from my 76 911's in favour of Webers. I have enjoyed the Webers a lot, the throttle response is vastly improved, and the noise is spectacular.
I have had some issues with clogging jets. This year I removed my tanks and cleaned it (used the electorlytic technique and it worked amazingly). In addition to cleaning up the fuel system, I decided it would be wise to invest in an EGT system, allowing me a much better read on how each cylinder is performing. I picked up and MGL avionics TC3 12 channel thermocouple display. I managed to get a killer deal on Ebay for 12 egt probes with a display head, that I bought just for the probes.
So this year I installed the thermocouples into the exhaust, and made up thermocouples for the CHT myself. For those I got a little creative, trying to install the plugs with a washer underneath to serve the thermocouple was difficult to achieve as the plugs are so deep. I decided instead to drill the corners of each plug base, on the wrenching surface (the top side of the hex throught the bottom) I then wired thermocouple wiring through the hole and around the plug base, creating a CHT probe. It has worked out very well so far!
So just last week I had a chance to fire her up with the sytem installed, and so far I feel it is paying for itself well. On initial startup, by reading EGT levels at various throttle positions I was able to ascertain that I have a few (3) clogged idle jets, progression holes impaired on two cylinders, and on blocked main jet. After cleaning all that up, managed to get her idling on all 6 and running normal parameters throughout the rev range. Even with the clean tank and lines, I think I will be having to eventually pull the carbs for another thorough cleaning, as I am still seeing jets clog from time to time. But with the thermocouples in place, no more guessing I can pull the affected jet and clean it back up knowing that is my problem area.
A handy system for a carb or ITB application, and I think it looks pretty cool too. I have uploaded a pic of the head unit.

the head unit requires final install, I will be making a bracket to get it mounted properly, the zip ties are temporary of course.

[gordner]

Another nice feature of the TC3 unit is the external alarm output, which I have wired to my EGR light. In the event of an excedence of the pre set EGT and CHT limit, a buzzer sounds and the TC3 unit activates the EGR light on the dash. Nice feature to avoid a clogged jet leaning out a cylinder to the point of valve damage.

[brighton911]

Very impressive. If you have pictures of the thermocouple installation, it would be nice to see.

[gordner]

I will be taking a few more tonight, just threw this up from work when I realised I had a few moments and the pic I posted already on my phone lol.

The installation was very straightforward, and I am very happy with it so far. I managed to do it for a reasonable cost, and it has provided a lot of information for sure.

[Bob Ashlock]

Definitely would like to understand/see how you did the spark plug thermocouples. I have struggled with a good solution for some time now, generally using the washer approach which is pretty difficult.

[Geneman]

very very cool please send pics of the egt probe setup and thermocouples. how much was the complete setup? would be great for my gestating itb track setup. thanks frank rauscher@wistar.org

[Dr J]

Looks good. I have been mulling over doing the same for some time but have decided to wait. Tell us what readings are you getting. Did you perforate the headers for the egt?

[gordner]

I will post a pic of a CHT set up plug soon, I think I have a spare left over that I prepped for install.

The cost was really affordable actually, mostly because of an Ebay deal for all the wiring and thermocouples. All together with the TC3 head unit and the rest of the items, I think I am in about $400, but I still have 6 spare probes worth about 50 a piece, and tons of wire left over too.
This shows an EGT probe, very simple to install, about 6 inches downsteam of the valve.
The harness routing, all in yellow is EGT. When i pull the motor next, I will re-run these wires to come down from above, and not be exposed to so much road debris.
This shows the CHT routing above the engine, the blue harness.
And here the wiring heading down to the plugs.

[gordner]

so for what values I have been seeing, the CHT runs a pretty narrow range, 180 right after start up, normal driving value about 200. 220 sitting in stop and go traffic on a hot day is the highest I have seen.
EGT at idle warm is about 950, peak at about 1600 running hard.

[snbush67]

I'm inspired! Thanks for sharing.