No direct aviation experience here, but on the test stand the placement

of

the EGT thermocouple has a surprisingly large effect on the temperature
reading. Not only distance from the port, but also depth into the

runner.

Peak temp will usually be at the centerline of the runner, but having a
thermocouple stuck that far into the stream increases the risk of

breakage.

Pull it back, and the temperature drops quite significantly.

Jon Lauter
Rotary Power Marine Corporation

Ed Anderson wrote:

Jon,
    I had EGT thermocouples in my 2" dia headers 8" from the exhaust port.
Initially, I was running approx 200F lower than others were reporting.  This
year I repace the thermocouples and my EGT was now reading what Tracy Crook
and others were reporting.  The Difference?  The orginal thermocouples were
approx 5/8" in lenght. the new ones are approx 1 1/4" in lenght.  This tends
to confirm what you mentioned about the lenght of the thermocouple.

Ed Anderson

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