Front Section
| ITEM | DESCRIPTION |
|---|---|
| A | Exhaust system front section - EU 6 market |
| B | Exhaust system front section - Northern American Specification (NAS) market |
| 1 | Pre catalyst Heated Oxygen Sensor (HO2S) mounting boss |
| 2 | Pre catalytic converter |
| 3 | Mid catalyst HO2S mounting boss |
| 4 | Support bracket |
| 5 | Main catalytic converter |
| 6 | Gasket to turbocharger |
| 7 | Post catalyst HO2S mounting boss |
The front section comprises a pre and a main catalytic converter. The catalytic converter is an emissions control device that converts toxic gases and pollutants in the exhaust gas to less toxic pollutants. This is achieved by catalyzing an oxidation and a reduction reaction.
The pre catalytic converter has a welded inlet cast cone with a flat face which mates with the turbocharger outlet. The flat face on inlet cast cone has a groove with a mica mesh gasket to seal to the turbocharger. Straight after the flange, the pipe contains a threaded boss for the installation of the pre catalyst Heated Oxygen Sensor (HO2S). The mid catalyst HO2S is located between the pre and the main catalytic converter. The main catalytic converter is secured to a transmission mounted bracket by a strap.
The pre and mid catalyst HO2S monitors the exhaust gases leaving the engine. The Powertrain Control Module (PCM) uses information from the HO2S to provide accurately metered quantities of fuel to the combustion chambers. This makes sure the most efficient use of fuel and to minimize the exhaust emissions.
For additional information, refer to: Electronic Engine Controls .
On North American Specification (NAS) market vehicles, an additional post catalyst HO2S is installed to the exhaust system.