Head Temp gauge and wiring, Dakota wire length and other items Options

[Ishley]

I've decided to add a head temp gauge to my '72 with a 2056 engine. I have several questions.

What is the right length wire to get? I see 18' on some sites... but that seems way too long. Anyone have experience? Maybe 14" is right. I'm planning to installed in in my console.

Can I add a thermo coupler/connector in the engine bay to make it easier to deal with if I drop the engine? K type with a Male/female connector.

I plan to push the wire thru the rubber gooseneck at the fire wall and route the wires down the inside along with all wires. I've done plenty of wire routing... and I hope this is the last time I'll do this.

I'm planning to drill a hole in my tin near the #3 plug... and add a rubber grommet for a clean installation.

Any other considerations before I place an order?

[FlacaProductions]

Hey Ed - I have the Dakota unit.
I have the 18 ft. cable and was told by Dakota:
The SEN-11-8 uses thermocouple wire, and as such it cannot be shortened. If you need a shorter cable you can purchase one here:
https://www.dakotadigital.com/index.cfm/pag...prod/prd115.htm

Otherwise you can coil up your extra cable and tuck it away.
====
Thats's exactly what I did - it's coiled up and secured behind the console gauge panel. I went this way because that length cable is the only one that has the proper (14mm) ring terminal.

there is a break (with little nuts and bolts) in the cable that should allow you a natural place to easily disconnect when you need to drop the motor. You can see it at the link above. Make sure you connect them in the correct orientation ("long" to "short" and "short" to "long" if that makes sense) otherwise you'll get some funky, incorrect readings. Ask me how I know.

Not sure a new hole in the tin would be the way to go - might make it difficult to get the ring around the plug and then threaded in. Mine goes thru the tin in the same hole as the #3 plug wire - I suppose if you want to get really fancy, you could thread the Dakota cable thru the plug wire grommet.

[emerygt350]

Did the same as flaca. Easy when dropping the engine because of the bit he mentioned.

[Ishley]

I’m not loving the connection between the engine and wiring harness. Maybe a sleeve over that.

[emerygt350]

I’m not loving the connection between the engine and wiring harness. Maybe a sleeve over that.

Yep.

[GregAmy]

The SEN-11-8 uses thermocouple wire, and as such it cannot be shortened.

Um, wut? Did they actually tell you that? Thermocouple leads are shortened all the time, it's just two wires that need a solid connection at each end.

Witness the wires that they offer to connect anyway, and ask them if there's a different gauge calibration based on the lead length (there's not; all the thermocouple does is generate a voltage differential that the gauge reads).

Likely they just don't trust you to properly terminate the other end with ring terminals; poor connections will affect readings. But the leads can decisively be shortened if you desire.

[FlacaProductions]

Yup - that's a direct quote.
I had room to bundle it all up neatly and since it works fine, just left it as-is...but I'm sure you're right.

[Montreal914]

I sure hope those loop screw connections are Chromel/alumel…

At one point I was considering having a panel with K-type connections in the engine bay for various temperature measurements (heads, EGT, others).

I would put a K-Type TC connector to facilitate engine removal.

I am not sure why they say the wire can’t be cut. (IMG:style_emoticons/default/confused24.gif) I believe the Dakota is a temperature compensated unit and should use K-Type wire from TC under the spark plug all the way to the gauge in the cabin. To be compensated, the gauge also reads the temperature of the connection point which could be hotter or colder than baseline room temperature depending on ambient temperature. It will then calculate/show the actual head temp no matter what ambient temp is around the gauge. This is very important!!

The VDO gauge was a mess as the TC wires were connected to copper wires (voltage leads) in the engine bay. Therefore temperature reference then became the engine bay temp, not room temperature. One could improve this by running TC wire up to the gauge as the cabin is closer to room temp than the engine bay is. But still, the gauge wasn’t thermally compensated and therefore ambient temperature should be part of the equation.

[Ishley]

Thanks everyone for your thoughts. I placed an order this evening.

I was looking into the K type male/female plug idea and it appears there are temp ranges. From what I could tell:

Mini plugs—-up to 300F or 400F
Full plug—- up to 400F
Hi-temp up to 800F. These I found on McMaster Carr. https://www.mcmaster.com/products/type-k-th...ple-connectors/


I’d like to do a plug… so I guess I go to hi temp ones. Admittedly I don’t quite understand the K Type details… I just want it to work well/right. McMaster is local here so I can drive over and spend a gallon in gas to save $13 shipping. I think I come out +5.

[emerygt350]

If you do any of those mods, be sure to test the system. Not something you want to be uncertain of.

[Montreal914]

The plug temp rating is simply for the environment these plugs will live in.
Use the mini plugs in the yellow plastic as they will live in your engine bay which is not a 400F environment. (IMG:style_emoticons/default/smile.gif)
The rating is for the yellow plastic itself, not the temperature that will be read by the thermocouple tip at yout spark plug.
Good luck! (IMG:style_emoticons/default/smash.gif)


EDIT: Make sure you keep polarity straight which is a little counter intuitive as red is negative.

[barefoot]

I used this (in 14 mm size) I think 3 meters long, long enough for under dash gauge.
Think i got it & cold junction compensated readout thru Amazon. Was pretty cheap.
I did bench calibration at room temp and in boiling water so know it's correct.