Front Section
| ITEM | DESCRIPTION |
|---|---|
| A | Exhaust system front section - Northern American Specification (NAS) market |
| B | Exhaust system front section - EU 6 market |
| 1 | Pre catalyst Heated Oxygen Sensor (HO2S) mounting hole |
| 2 | Pre catalytic converter |
| 3 | Mid catalyst HO2S mounting hole |
| 4 | Main catalytic converter |
| 5 | Post catalyst HO2S mounting hole |
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 by catalyzing an oxidation and a reduction reaction.
The pre catalytic converter has a welded pipe which is flared into a cone and mates with the turbocharger outlet. The connection is sealed with a stainless metallic gasket to the turbocharger and secured with a locking ring flange onto the turbocharger housing. Straight after the flange, the pipe contains a threaded hole 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. On North American Specification (NAS) market vehicles an additional post catalyst HO2S is installed to the exhaust system, which is located after the main catalytic converter. The main catalytic converter is secured to the engine mounted bracket by a strap.
The pre, mid and post catalyst HO2S monitors the exhaust gases leaving the engine. The Powertrain Control Module (PCM) uses the 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