Tube Going To Cat
 

Can someone please explain to me the mechanics of the tube going to the cat. I know that there is a smaller tube off the larger diameter one that goes to the actuators. My question is that is air blowing to the cat through there or is air blowing from the cat back into the engine? in other words chich way is pressure flowing?

Thank anyone in advance for the help

david

air going into your cat. its how catalysts (in this sense) work. the cat uses the air in it second "section" to convert leftover HCs (etc) to less HCs, CO2 (hopefully very little CO), and NOx. also, a bit of H2O can be a 'by-product' of the cycle.