Catalytic Converter (CAT) ’K’ Series (Emission control)

Catalytic Converter (CAT) ’K’ Series

The CAT is mounted between the front pipe and the intermediate pipe assemblies. A flange is welded to each end with three captive bolts in each flange. The CAT is connected to the mating flanges of the front and centre silencer assemblies and secured with three nuts on each flange. A metal gasket seals each flanged joint.

The CAT is fabricated from stainless steel and welded fully at all it’s joints. The catalyst element comprises of a ceramic element which is formed into a honeycomb of small squares. The ceramic element is coated with a special surface treatment called ’washcoat’. The washcoat increases the surface area of the catalyst element by approximately 7000 times. A coating is applied to the washcoat which contains the precious metals Platinum, Rhodium and Palladium.

The metallic coating of platinum and palladium oxidize the carbon monoxide and hydrocarbons and convert them into water (H₂O) and carbon dioxide (CO₂). The coating of rhodium removes the oxygen from nitrogen oxide and converts it into nitrogen. The efficient operation of the CAT is highly dependant on the content of oxygen in the exhaust gases which is controlled by the ECM in response to signals from the heated oxygen sensor.

NOTE: Refer to the Engine Management - MEMS section for a desciption of the heated oxygen sensor.

CAUTION: The catalytic converter will be irreparably damaged if leaded fuel is used. Leaks in the exhaust system will also damage the catalyst by drawing oxygen into the exhaust system which causes the catalyst to overheat. Engine misfires can cause overheating of the catalyst which may lead to overheating and melting the element and partially blocking the exhaust system. Only use unleaded fuel, the filler neck is designed to accommodate only unleaded fuel pump nozzles.

Exhaust Gas Recirculation (EGR) - ’L’ series models

Freelander vehicles fitted with the 2.0 L-series engine utilise an EGR System to reduce NO_x emissions. This is achieved by recirculating exhaust gases back into the combustion process which reduces combustion temperature by delaying the fuel burning rate.

Recirculating too much exhaust gas can result in higher emissions of soot, HC and CO due to insufficient air. Therefore, the precise quantity of recirculated gas is controlled by the Engine Management System - EDC to ensure the optimal operating conditions are maintained.

The exhaust gases pass through an EGR cooler before they are mixed with intake air. The EGR cooler is mounted on the side of the EGR valve which is located on the exhaust manifold. The EGR cooler receives coolant from the cylinder block which then circulates through the cooler to cool the exhaust gases. The cooled gases are drawn from the cooler and mixed in the inlet manifold with the intake air from the intercooler.

NOTE: Refer to the Engine Management System - EDC section for additional descriptions and operations of components and related systems affecting the limitation of emissions (such as the intake air system and fuel injection control).

See ENGINE MANAGEMENT SYSTEM - EDC, Information.