Q: about various types of EGT probes.

[Fran and Bud]

Mike,
The letter designation describes the Type of the thermocouple and its normal
range. 
"J" and "K" are pretty common (US). Also B, C, E, N, R, S, T. 

"J" is made of Iron (+) (White) and Constantan (-) (Red) and has a useful
range of about 200 to 1400 F.

"K" is made of Chromel (+) (Yellow) and Alumel (-) (Red) and has a useful
range of about 200 to 2300 F.  MOST APPROPRIATE FOR RACE CARS (opinion, not
fact).

We use a "K" in each of the collectors (2) of a Bonneville car and they read
1350 nominal on a dashboard pyro gauge when the engine is fat - and will
climb fast as/if it goes lean.
Note:  This is in 3 1/2 inch collectors 3 feet from the cylinder head - 
not right at exhaust port as in data logging of each cylinder..

Parts for a typical lo-buck approach (non data logger) should cost somewhere
around:
Dash Gauge 125 to 150 US;  Thermocouple 25 to 35 US each; Extension leads
(same materials as thermocouple)15 to 20 US each. 
(Dont extend leads with copper wires, creating additional dissimilar metal
junctions)

Most common automotive application is for Diesel Big Rigs, and if you have
access to
a friendly big rig parts house or a big rig wrecking yard you could get
lucky and come up with 
an inexpensive system that will tell you a lot about how the engine is
running.
HTH
Bud          

----------
>From: "Diehl, Jeffrey" <jdiehl at sandia.gov>
>To: "'diy_efi at diy-efi.org'" <diy_efi at diy-efi.org>
>Subject: Q: about various types of EGT probes.
>Date: Thu, Sep 6, 2001, 11:54 AM
>

>Hi all,
>
>I'm looking into putting one or more exhaust temp probes in one of my cars.
>While pricing the probes, I was asked what type of probe I need.  Quick
>research on the Web revealed that these probes are designated as K-type,
>J-type, N-type, etc.  Does anyone know what this refers to?  Is it form
>factor, or electrical characteristics, for example?
>
>Any source of information on the topic would be most appreciated.
>
>Thanx,
>Mike Diehl,
>
>
>
>
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