Carbon Canister

[azzkikr]

What exactlly does the carbon canister do? Does it put air back into the fuel tank or does it trap fuel vapor on hot days? I see there is an expansion tank so I assume that catches the vapor. The canioster seems to feed from the intake manifold so I dont know if its pumping vapor into the intake or putting air into the fuel tank. Not sure which way it goes.

[rs4pro3]

It stores fuel vapor, on the 325i cars when your are coasting a valve opens letting the fumes back into the intake so they can be burned off in the engine.