Just out of curiosity, has anyone ever used a sensor or readings to prove any difference?
I purchased a 5 dollar Ice Warner device deal that has the really long wire with a temp probe on it. Used for warning of ice of course, but I placed the sensor securely inside the air intake track just before the throttle body.
When I made a homemade ram air deal using ducting and the stock air box I could see that the air intake temps were always less than 10 degrees off (warmer) of outside temp. When I reinstalled A/c I did away with the ram air and the stock airbox draws in air from the fender and engine bay.
While driving and moving at constant speed I noticed nothing more than a 15-20 degree difference in intake charge and outside air, where as sitting the air would get way warmer. After sitting the sensor would read over 100 degrees in the summer after engine shutdown and heat soak but would drop quickly once started up.
What I am saying is the stock air box does not to bad of a job even when opened to the engine bay when your moving. I have yet to actually install a true CAI to test with the temp readings but I expect the same as my Ram Air deal, 10 degree or less difference in intake charge and ambient.