Catch Cans are an often overlooked but crucial component of any performance car. In a combustion engine, the air that manages to push its way past the pistons rings will create pressure inside the crankcase. This pressure will need to be able to escape to prevent build up in the crank case. If not allowed to escape this build up over time could lead to gasket failures in the engine anddecreased power by creating a restriction on the bottom side of the piston during the combustion stroke. In the past engines were allowed to vent to the atmosphere. Beyond the obvious emission concern there is a power advantage to pulling the air out with a vacuum. This advantage is created by greatly decreasing the pressure on the bottom side of the piston. Modern cars pull this air out by pluming the crankcase back into the engines intake manifold for the gasses to be burned off with the incoming fresh air. The PCV (Positive Crankcase Ventilation) system typically does not have an adequate filtration mechanism to remove oil and other contaminants suspended in the air. This effectively lowers the octane rating of your fuel, fouls plugs, and reduces the life of the engine. A catch can is used to separate theses particles from the air before adding it to the fresh air stream.