System Description

Exhaust System Description
^ The purpose of the exhaust system is to convey engine emissions from the exhaust manifold to the atmosphere.
^ The underbody catalyst may be in-line with the the light off catalyst, or the underbody catalyst may be common to two light off catalysts, forming a "Y" pipe configuration.

Exhaust System Operation
^ Engine exhaust emissions are directed from the engine exhaust manifold to the catalytic converter through the front exhaust pipe. The reduced exhaust emissions are then directed from the catalytic converter to a muffler through the rear exhaust pipe. Lastly, the exhaust emissions are directed to the atmosphere through an exhaust pipe.

Exhaust Manifold
^ Collects exhaust gases from the engine cylinders.

Heated Oxygen Sensors (H02S)
^ Provides the powertrain control module (PCM) with voltage and frequency information related to the oxygen content of the exhaust gas, (how rich/lean the engine is operating).
^ Upstream H02S signal serves as an input to the H02S monitor.





^ Downstream H02S signal is an input to the Catalyst Efficiency monitor and may be located after the light off catalyst or underbody catalyst.

Three Way Catalytic Converter
^ Contains either platinum (Pt) and rhodium (Rh) or palladium (Pd) and rhodium (Rh).
^ Catalyzes the oxidation reactions of unburned HCs and CO and the reduction reaction of NOx. The three-way conversion only occurs with the air fuel/ratio near stoichiometry.

Exhaust Pipes
^ Exhaust pipes are usually treated during manufacturing with an anti-corrosive coating agent to increase the life of the product.
^ Serve as guides for the flow of exhaust gases from the engine exhaust manifold through the catalytic converter and the muffler.

Muffler
^ Usually treated during manufacturing with an anti-corrosive coating agent to increase the life of the product. Reduces the level of noise produced by the engine and reduces the noise produced by the exhaust gases as they travel from the catalytic converter to the atmosphere.