194003904 - INTRODUCTION - EXHAUST EMISSION CONTROL SYSTEM

DESCRIPTION OF COMPONENTS

CATALYTIC CONVERTER

Specifications

The catalytic converter is a post-treatment device for oxidizing the CO, HC and particles transforming them into carbon dioxide (CO2) and water vapour (H20).The catalytic converter consists of a ceramic, honeycomb structure (1) with cells impregnated with platinum (2) which catalyzes the oxidation reactions.

Operation

The exhaust gases passing through the cells heat the catalyzer triggering off the conversion of the pollutants into inert compounds.The oxidizing chemical reaction of the CO, HC and particles is effective at temperatures of between 200 and 350°C.In effect, above 350°C the sulphur contained in the diesel fuel starts to oxidize producing sulphur dioxide and sulphur trioxide.

DPF SYSTEM (Diesel Particulate Filter)

This is a mechanical filter that "traps" the carbon particles (particulate) and the engine oil ashes in the exhaust gases in diesel engines.The action of the DPF makes it possible to keep carbon particle levels down by around 90% in line with Euro 4 and 5 regulations.The operation of the DPF system is managed by the engine injection control unit by means of suitable strategies. In addition to the actual filter the DPF system comprises an exhaust gas temperature sensor and a differential pressure sensor.The differential pressure sensor measures the pressure of the exhaust gases upstream and downstream of the filter, by means of special pipes, signalling the gradual accumulation of particulate to the control unit. The particulate accumulation process and the relative increase in the pressure of the exhaust gases inside the filter depends on the engine load, the weight of the vehicle and the engine capacity and power. Therefore the particulate needs to be removed on a regular basis, regenerating the filter following a procedure that makes use of multiple injections to increase the temperature of the exhaust gases (about 600°C) and burn the particulate. The regeneration procedure is controlled by the injection control unit which acts: on the metering of the fuel (up to five injections in the same engine cycle per cylinder) and on the control of the air (E.G.R. and supercharging pressure).The regeneration phase takes place over a few minutes and does not affect the continuity of the torque supplied by the engine in terms of normal operation.1. Turbocharger-exhaust manifold assembly2. Catalytic converter3. Filter4. Exhaust gas pressure intake5. Exhaust gas temperature sensor downstream of the catalyzer6. Exhaust gas temperature sensor downstream of the filter7. Differential pressure sensor8. Injection control unit