184000289 - 1080B EXHAUST EMISSION CONTROL SYSTEM

COMPONENT DESCRIPTION

Catalytic converter

The oxidizing catalytic converter is a post-treatment device for oxidizing the CO, HC and particle matter, transforming them into carbon dioxide (CO2) and water vapour (H2O).The catalytic converter consists of a ceramic, honeycomb structure monolith (1) with cells impregnated with platinum (2), which acts as a catalyst for the oxidation process.The exhaust gases which pass through the cells heat the catalyzer, triggering the conversion of the pollutants into inert compounds.The chemical reaction which causes the oxidation of the CO, HC, and particle matter takes place at temperatures of between 200 and 350°C.In effect, at temperatures above 350°C the sulphur, contained in the diesel fuel, starts to oxidize, producing sulphur dioxide and sulphuric anhydride.

LAMBDA PROBE

The 'EUGO' planar type linear Lambda sensor is fitted on the catalytic preconverter and informs the engine management control unit concerning the combustion progress.The sensor is an oxygen sensor containing two comparative cells which make it possible to measure the λ values (ratio between the quantity of air drawn in and the theoretical quantity of air required for the complete combustion of the fuel injected) within a broad range from λ=0.7 (rich mixture) to the air value (λ = (poor mixture).It is used to compare the reading of the air flow meter with the control unit map and, if necessary, corrects the injection of fuel to be within the emission limits.The operation of the sensor takes place by comparing the concentration of oxygen present in the reference cell, housed inside the sensor, with the combustion gas flowing inside the comparison cell next to the reference cell. Depending on the resulting imbalance, the engine management control unit regulates a current signal (lp) which rebalances the oxygen content of the comparison cell through an electro-chemical action. The value of lp is proportional to the value of λ measured in accordance with the trend shown in the graph below.
In order to activate the operation of the sensor quickly, the sensor contains a heater operated in duty-cycle by the engine management control unit according to a calibrated strategy.The two comparison cells and the heater are integrated in the same planar ceramic element (layering of several ceramic elements) in order to make the structure compact and guarantee high response speeds and heating of the actual element.
1. Connecting cable2. Protective sleeve3. Planar sensor element4. Ceramic support pipe5. Sensor housing6. Ceramic seal7, Protective tube

ELECTRICAL SPECIFICATIONS

  • Max heater power supply 7.5 V from control unit
  • Heater resistance 3.2 ± 0.8 O