Omega thermocouples

[Charles]

	I have had some experience with pyrometers a.k.a. exhaust gas
temperature meters.
	I bought the gauge from AutoMeter for about $75 (comes with the
amplifier module) and then discovered they wanted another $100 for a
thermocouple! So I called Omega, and tried an open-junction 1/16"
K-type. It lasted about 10 minutes. I should have known that the
vibration would break the little weld ball off where the wires meet
(the actual thermocouple).
	Then I tried a 1/16" enclosed end, 321 stainless. This responds a
little slower, but will last for about 3 months or so (not so good at
$31 each). The end just burns right off, especially when doing lots of
full-boost blasts at 1600 F temperature.
	321 is not supposed to do this. Omega thinks it's a combination
of corrosive gas, extreme temperature, and vibration. They suggest
going to a 1/8" (but this will slow the response). Also the stainless
compression fitting is irreversibly bonded to my exhaust manifold
despite the use of copper anti-seize paste...
-Charles
'81 745i
p.s. I usually saw about 1050 F at idle (retards to 1 BTDC for lower
idle emissions). About 1250 F at part throttle cruise, and up to 1600
=46 at 15 psi boost. It's interesting to observe the effect of changing
the AF meter flap tension on exhaust temps...