Why is it that cats function properly when warmed up and not cold?

Also, how does the AIR pump inject air hotter than exhaust temps?

 

The air pump doesn't inject hotter air, it just injects air. I'm not too confident on the theory behind it, but i think the oxygen causes some sort of reaction with the metals in the converter.

Someone smarter will pipe up.

 

the cats function properly when warm because the whole purpose is to burn off excess carbons and such that are not spent by the motor. so when the cat is cold its not burning anything, but when they get hot the exhaust stays hot and more pollutants are burned.

 

The purpose behind the air pump is to inject air during startup where the car is intially running richer to reduce emissions.

 

The platinum, palladium and rhodium catalysts used on the converters are not active until they reach about 600-degF. There are both oxidation ("burning") and reduction reactions taking place on the surface of the catalyst substrate.

The air added to the exhaust gasses combines with unburned HC's from the overly rich cold-start mixture, and releases heat that brings the catalyst up to temperature faster.

 

damn Fred you're like a f'n encylopedia!