Exhaust System: Description and Operation
EXHAUST SYSTEM COMPONENTThe exhaust system consists of the components shown in the following illustrations.
Exhaust System 2.3L Engine
Exhaust System Components - 2.3L:
1-13:
Exhaust System 4.0L Engine
Exhaust System Components - 4.0L:
1-13:
Exhaust System
The purpose of the exhaust system is to convey engine emissions from the exhaust manifold to the atmosphere. Engine exhaust emissions are directed from the engine exhaust manifold to the catalytic converter through the front exhaust pipe. A Heated Oxygen Sensor (HO2S) is mounted on the front exhaust pipe before the catalyst. The catalytic converter reduces the concentration of carbon monoxide (CO), unburned hydrocarbons (HCs), and oxides of nitrogen (NOx) in the exhaust emissions to an acceptable level. The reduced exhaust emissions are directed from the catalytic converter to a muffler through the rear exhaust pipe. Another HO2S is mounted on the rear exhaust pipe. Lastly, the exhaust emissions are directed to the atmosphere through an exhaust pipe.
Exhaust Manifold
The exhaust manifold collects exhaust gases from the engine cylinders. The number of exhaust manifolds depends on the engine configuration and number of cylinders.
Heated Oxygen Sensors (HO2S)
^ The HO2S provide the Powertrain Control Module (PCM) with voltage and frequency information related to the oxygen content of the exhaust gas. In addition to providing the PCM with indications of how rich/lean the engine is operating, the upstream HO2S signal serves as an input to the HO2S monitor. The downstream HO2S signal is an input to the Catalyst Efficiency monitor. The downstream HO2S may be located after the light off catalyst or underbody catalyst. The underbody catalyst maybe in-line with the light off catalyst, or the underbody catalyst may be common to two light off catalysts, forming a "Y" pipe configuration.
Three-Way Catalytic Converter
^ The three-way catalytic (TWC) converter contains either platinum (Pt) and rhodium (Rh) or palladium (Pd) and rhodium (Rh). The TWC converter 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. The pipes serve as guides for the flow of exhaust gases from the engine exhaust manifold through the catalytic converter and the muffler
Muffler
^ Mufflers are usually treated during manufacturing with an anticorrosive coating agent to increase the life of the product. The muffler reduces the level of noise produced by the engine, and it also reduces the noise produced by the exhaust gases as they travel from the catalytic converter to the atmosphere.