I finally got the turbo installed, did some break in runs, then hit full boost a few times.
I am surprised by how long it takes for the intake air to heat up, relative to when boost comes on to max (~7 psi) and then how very slow it is to cool down.
Is this typical? Is it sensor lag (RC time constant)?
Could it really be "heat soak" at 68 ° F?
Does the body of the IC heat up that much and then hold on during boost?

Flyin Miata intercooler, Garret 2560 turbo, 2001 Miata
GM IAT mounted on the output side of IC, facing forward, inside the large zone of the bumper skin.
Ambient temp 58 F.

Upper red trace the boost
Lower red trace the intake air temp
AFR sensor failed so ignore that.

 

Yes, the IC has a significant amount of thermal mass. Notice how long it takes to cool down from peak.

 

Also slow to cool as you have closed the throttle so air flow across the cooler and MAT sensor has turned to a trickle. You can play with this live with your throttle on a fast sensor and see what difference the airflow makes.