Emission Control Systems: Description and Operation

The emission control systems are used to reduce harmful gases (CO, HC, and NOx) in the combustion engine exhaust.
The emission control system has the following three major systems:

1. Crankcase emission control system.
The crankcase emission control system is a system adapting a closed-type crankcase ventilation, to prevent blow-by gases from escaping into the atmosphere. The blow-by gases in the crankcase are routed back to the intake manifold for combustion.

2. Evaporative control system.
The evaporative control system prevents the escape of fuel vapors from the fuel tank and carburetor or fuel injection into the atmosphere. It consists of various components, which collect and lead the fuel vapors to the intake manifold for combustion.

3. Exhaust emission control system.
The exhaust emission control system consists of a oxygen sensor, three-way catalytic converter and some models are equipped with an air injection system.

Porsche uses one or more of the following emission control systems on their engines depending on country, state, year model and engine (the specific emission control systems used on your vehicle are listed under "SYSTEM I.D."):

-AIR INJECTION SYSTEM (AIR)
-DECELERATION VALVE (DCV)
-EVAPORATIVE CONTROL SYSTEM (ECS)
-OXYGEN SENSOR (OXY)
-POSITIVE CRANKCASE VENTILATION (PCV)
-THREE-WAY CATALYTIC CONVERTER (TWC)