which thermocouple for Isspro EGT?

[roverhybrids]

which thermocoupler probe do I want to go with my Isspro EGT?
Also need the lead wire too.

I plan on mounting the gauge in a triple pod above the mirror.

lead wires:
http://www.isspro.com/products.php?cat=66

EGT probes:
http://www.isspro.com/products.php?cat=68

 

[Silverbullet]

I am running the R650S. That is the short one that is still adjustable. I dont know as far as the wire goes.

 

[rbattelle]

IIRC, I have an R650PL and an R660-10PL. I like the plug connectors.



-Ryan

 

[roverhybrids]

thanks for the replys.

I went with the R658S.
Isspro tech said just use wire for the lead wire.

 

[rbattelle]

thanks for the replys.



I went with the R658S.

Isspro tech said just use wire for the lead wire.

Ummm... what? You do realize you cannot use ordinary wire for the lead wire, it must be thermocouple wire. If they told you that at Isspro then you got someone who doesn't know what they're talking about.



DO NOT USE ORDINARY WIRE ANYWHERE BETWEEN YOUR THERMOCOUPLE AND YOUR GAUGE!



-Ryan

 

[roverhybrids]

Yes, the tech guy at Isspro told me directly to "just use solid core copper wire". I then asked if I could just use multi-stranded copper wire and he said YES.

I installed an Isspro EGT on another vehicle before and asked about cutting the length of the lead wire and Isspro tech told me I could trim it to whatever length I wanted.

This leads me to believe that the gauge just reads the resistance in the thermocoupler and the wire doesn't have much effect as long as it's within reasonable limits.

BUT! I will ask again tomorrow to be sure(er)

 

[rbattelle]

This leads me to believe that the gauge just reads the resistance in the thermocoupler and the wire doesn't have much effect as long as it's within reasonable limits.

This is not how a thermocouple works. A thermocouple reads a voltage generated from a thermal gradient along a two wires of dissimilar metals shorted at one end. So if you introduce another metal junction somewhere in the line between the gauge and the thermocouple, you will alter the readings. Instead of reading the temperature at the thermocouple, you'll read some weird amalgamation of the temperature at the thermocouple and the temperature at the junctions you made with the copper wire. Your gauge, in effect, becomes useless.



That's why they sell lead wires in the first place! If you could simply stick any kind of wire you wanted on a thermocouple, then why in the world would anyone spend the money for a lead wire?



I don't know why Isspro tech support would be telling people the exact opposite of how I understand the function of a thermocouple unless my understanding is completely false.



Here's a decent discussion of how they work.



-Ryan

 

[roverhybrids]

So I called tech support again this morning and the tech guy told me that the lead wire is not needed on the EV series gauges; which is what the new ones for the Dodge trucks are as well as some others. So with the new Isspro gauges you can use ordinary copper wire#ad

 

[rbattelle]

Okay, then the only thing I can think of is they've moved the cold junction temperature terminals to the thermocouple itself. That makes almost no sense to me, but I guess it's possible. Maybe. It suggests you'd have to use only certain types of thermocouple with the new EV gauges.



Maybe I'll send them an email...



-Ryan