2750891 - 1080B exhaust emission control system

Specifications

Of the 'planar' type, it is mounted on the front section of the exhaust pipe, and it informs the control unit about the combustion trend (stoichiometric ratio).To obtain an optimum mixture, the quantity of air drawn in by the engine is the same as the theoretical quantity that would be needed to burn all the injected fuel.In this case the Lambda factor (λ) the ratio between the quantity of air drawn in and the theoretical quantity of air (needed to burn all the injected fuel), is 1.

Thus:

• λ = 1 ideal mixture
• λ > 1 lean mixture
• λ < 1 rich mixture

a, Rich mixture (too little air) b, Lean mixture (too much air)

Specifications

The Lambda probe, placed in contact with the exhaust gases, generates an electrical signal whose voltage depends on the concentration of oxygen present in the gases.This voltage undergoes a sudden variation when the composition of the mixture moves away from the value λ = 1.The heating of the Lambda probe is managed by the fuel injection control unit in relation to the exhaust gas temperature.This avoids thermal shocks on the ceramic casing due to the contact with condensed water, present in the exhaust gases when the engine is cold.The measuring cell and heater are built into the 'planar' (stratified) ceramic element, with the advantage of obtaining quick heating of the cell, thus permitting a closed loop' check (λ = 1 within 10 seconds of engine start-up.1, Connecting element 2, Protective sleeve 3, Planar sensor element 4, Ceramic tube casing 5, Sensor housing 6, Ceramic seal 7, Protective tube

Specifications

The operation of the Lambda probe is based on the principle of an oxygen concentration cell with solid electrolyte.The surfaces of the measuring cell are coated with microporous layers of noble material.1, Exhaust gases 2, Passage of reference air 3, Heater 4, Lambda probe voltage

Specifications

Electrical characteristics

• Heater supply: 12V
• Heater resistance: 0.5 - 1 kOhm.

The three-way catalytic converter simultaneously reduces the three polluting gases present in the exhaust gases:

• unburnt hydrocarbons (HC);
• carbon monoxide (CO);
• nitrogen oxides (NOx).

Two types of chemical reactions take place in the converter:

• oxidation of the CO and HC, converted into carbon dioxide (CO₂ ) and water (H₂ O)
• reduction of the NOx converted into nitrogen (N₂ ).

The converter consists of a monolith, a metal mesh support for damping impacts and vibrations and an outer stainless steel housing resistent to high temperatures and atmospheric agents.The monolith consists of a honeycomb structure comprising a ceramic material coated with a very thin layer of catalytically active substances, platinum or rhodium. These accelerate the chemical decomposition of the harmful substances contained in the exhaust gases which, passing through the core cells at temperatures of over 300°-350° C, activate the catalyzers, thus starting the oxidoreduction reactions.To optimze the efficiency and duration of the catalyzer, a perforated plate metal cone improves the diffusion of the exhaust gases in the cells of the ceramic core.1, Ceramic monolith 2, Metal support 3, Outer casing 4, Perforated plate metal cone

The noble metals contained in the catalytic converter, because of the high temperature, are chemically attacked if lead is present. For this reason the use of petrols containing lead should be avoided, otherwise the converter will be quickly and irreversibly damaged. Never use petrol containing lead, not even in an emergency or for a very short time.

In the case of the CEE STAGE 4 homologated engine, the catalytic converter differs considerably through the composition of the ceramic structure coating which is different due to the increased quantity of noble metals contained.