Posted for "bob mackey" <n103md@yahoo.com>:

> The TIT GAS is cooler than the exhaust GAS...
> it's further down the line... it's had time to cool more.

> So, why does TIT READ higher?

The exhaust leaving the exhaust port cools because it expands.
Putting a second probe further down the pipe will show a lower
temperature IF the gases have expanded on their way to the
second probe. On the other hand, if there is some restriction
in the flow path (like a turbine) that has kept the pressure
from dropping, then the temperature will not drop either.

PV = nRT
(still true 87 years after Nernst got his Nobel prize)

There are second and third reasons why the TIT is typically
higher than the open-pipe EGT. The lower compression ratio
with the turbo engine means that the combustion gases have
expanded (and cooled) less than in the normally-aspirated
engine. Also, the turbo engine may have had a higher intake
gas temperature (and pressure) before compression and combustion.

-bob