Drawing air from the warmer rear, upper area of the engine compartment, as opposed to your average Lycoming or Continental that draws air directly from outside (when carb heat is "off") is a big difference in my mind. I'd like to instrument that area with a thermocouple some day and measure what the temperature is compared to the outside air temp. It would be useful to do that several different times under various ambient conditions. For the record, I don't have carb heat for my 912 ULS either.