A Volkswagen Golf TDI 6 and in the background an American city: from its overseas started the investigation on pollutant emissions that led to unveil a software irregular in cars equipped EA 189 engine.
TWO DIFFERENT WORK – The Volkswagen has unveiled what constitutes intervention, but now merely talk about rehabilitation. Therefore we do not know if the change only interests the software part or whether it can also extend to the hardware, or the physical components. The engine indicted, remember, has project code EA189, complies with the Euro 5 and was also mounted on 482,000 cars sold in the US between 2009 and 2014. Experts quoted by Automotive News which refer precisely to the models sold in the US, argue that interventions should be considered easier when the engine goes back to the period between 2009 and 2012, so that older units may need only a software change. The reason is explained by the use of the least processed of the catalysts to nitrogen oxides, called in jargon Lean NOx Trap.
In the above drawing an example of installation of reduction of pollutant emissions Rankings on that of the Volkswagen engine EA 189 sold in the US until 2011. From left the traditional oxidation catalyst, which neutralizes the carbon monoxide (CO) and unburned hydrocarbons (HC), the lean NOx catalyst that reduces nitrogen oxides (NOx), and finally, the particulate filter.
HOLDS NITROGEN – This type of catalyst works similar to a standard filter, which also is present in all diesel starting at Euro 5: retains oxides of nitrogen (NOx) in its interior to the passage of the exhaust gas thanks to a chemical reaction and, periodically, it is “cleaned” by powering the motor with a richer mixture. At this point the nitrogen oxides, which may be irritating to the respiratory tract, are transformed into common and harmless nitrogen. Defects of Lean NOx Trap are the frequent “cleanups” catalyst, that increase consumption of the car, and the performance that is highly dependent on conditions of use. For example in the car charging or at high speeds the performance declines significantly.
Above a drain line of the Volkswagen that uses the most sophisticated SCR catalytic converter (Selective Catalytic Reduction). This is after the oxidation catalyst, which reduces carbon monoxide (CO) and unburned hydrocarbons (HC), and is followed by the filter.
THE IF SCR – the opposite case if the engine Volkswagen EA189 is newer than 2012: in this case the houses have expected a more sophisticated and expensive catalyst for NOx called SCR (Selective Catalytic Reduction). In what experts say, in this case the engine may need additional interventions to the physical components of the car. For the Volkswagen Group would mean a multiplication of the intervention costs that someone estimated to be higher than the 6.5 billion already allocated by the house to deal with the situation.
In the photo above the particular injection of AdBlue urea inside the SCR which occurs in a continuous manner during driving. A command its dosage thinks the unit according to the demands of the engine.
IT TAKES The AMMONIA – The SCR works by adding the exhaust gas passing through an additive nebulized called AdBlue, a solution based on urea. This solution at high temperature breaks down creating the component that serves as a reagent for nitric oxide, that is, the ammonia. This is deposited in the catalyst and the passage of the exhaust gas combines with NOx through a reaction which generates nitrogen (N) and water (H 2 O), completely harmless. The main advantage of the SCR catalyst is increased efficiency, for which up to 95% of the nitrogen oxides are converted. Disadvantages are the higher initial cost of the technological solution and the need to periodically refill the additive AdBlue, which normally is done at each cutting from the service network. That of the SCR catalyst is therefore establishing itself as the preferred solution by most manufacturers.
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