Emission control devices

EMISSION CONTROL DEVICES

The devices used are designed to reduce the harmful substances present in the exhaust (catalytic converter) and eliminate the evaporation of the fuel towards the outside (anti-evaporation system).

THREE WAY CATALYTIC CONVERTER

The check on the mixture strength, closed-loop, is activated from the Lambda sensor which measures the oxygen content in the exhaust gases upstream of the catalyzer.

The Lambda sensor measurements allow the electronic control unit to constantly correct the mixture strength keeping the air/fuel ration constant.

In this way the harmful exhaust emissions are kept in check which is also the job of the three way catalytic converter.

The efficient operation of the catalytic silencer and consequently containing the toxicity of the exhaust gases depends on the air/fuel ratio which the engine receives.

The three-way catalytic converter makes it possible to simultaneously restrict the three pollutant gases present in the exhaust gases: unburnt hydrocarbons (HC), carbon monoxide (CO), nitrogen oxide (NOx).

Two types of chemical reaction take place inside the converter:

• oxidation of the CO and the HC, converted into carbon dioxide (CO2) and water (H2O)
• reduction of the NOx, converted into Nitrogen (N2).

1. Cermanic monolith
2. Metal support
3. Steel outer casing

The converter is made up of a monolith (1), a metal gauze support (2) to dampen the impacts and vibrations to the core and an stainless steel outer casing (3) which is resistant to high temperatures and atmospheric agents.

The monolith is made up of a honeycomb structure composed of a ceramic material coated with an extremely thin layer of catalytically active substances, platinum or rhodium, which accelerate the chemical decomposition of the harmful substances contained in the exhaust gases which, passing through the core cells at temperatures in excess of 300 - 350 °C, activate the catalysts thereby setting off the reactions of oxidation and reduction.