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This Is How Audi Reduces the Emissions of Its Gasoline and Diesel Engines

Part of the Volkswagen Group, the Ingolstadt-based carmaker is no stranger to emission standards. With government agencies breathing down their necks and stricter European legislation, Audi is effortlessly developing and enhancing technologies for cleaner, more efficient engines.
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Among the pollutants that gasoline and diesel engines emit are nitrogen oxides, or NOx. They have harmful direct effects on our health and an indirect effect on the environment through the damage they do to ecosystems and agriculture.

Reducing emissions has become a priority for governments and the private sector in most parts of the world, and nowhere is this more evident than in the automotive industry.

Twenty years ago, in Europe, a diesel-fueled car could be approved for road use if it did not exceed the Euro 3 NOx emission limit, which was set at 500 mg/km.

The Euro 6d limit introduced earlier this year stands at only 80 mg/km. This highlights how much stricter legislation has become, especially after the 2015 Dieselgate scandal.

On the old continent diesel engines are still very popular, and despite the scandal, VW Group diesels are still the first choice of many Europeans.

Audi is part of the development process for the new generation of the V6 TDI, and being aware of its immense popularity, has developed a new exhaust after-treatment system that complies with the strict regulations while offering a powerful, cleaner and more efficient engine.

Although it was a huge challenge to design a system that requires larger catalytic converters, the engineers managed to build a compact system that incorporates all the latest gas purification technologies.

It features an oxidation catalyst (NSC) and an SCR-coated diesel particulate filter (SDPF), which are placed close to the engine, near the exhaust turbocharger. Also, a second SCR catalytic converter is placed further down the exhaust system, bellow the vehicle’s underfloor.

The NSC can temporarily store nitrogen oxides and uses their oxygen molecules during the regeneration process to oxidize unburned hydrocarbons and carbon monoxide into carbon dioxide and water vapors.

Another battle in the war against nitrogen oxides is carried out using the AdBlue additive. The exhaust features a twin dosing system that injects the additive at two points.

One of the dosing modules is placed near the SDPF, and the other further down, near the second SCR. The use of this technology enhances the effectiveness of the exhaust system, converting more than 90 percent of the nitrogen oxides.

To combat emissions in turbocharged direct-injection gasoline (TFSI) engines, Audi uses various technologies and components to reduce fuel consumption and purify the exhaust gasses, with the most important being the gasoline particulate filter (GPF).

It works by directing exhaust gases through porous ceramic cell walls with particles sticking to the ceramic surface. They are then neutralized through a similar regeneration process as the diesel particle filters.

This reduces carbon particulate emissions caused mainly when cold starting a gasoline engine by as much as 90 percent.

Audi uses huge GPFs, for example, on the EA888 2.0-liter four-cylinder engine the filter has a volume of 3.2 liters. The filter is continuously sensor-monitored, and the central unit adapts the frequency and duration of the regeneration process based on the actual driving style of each customer. Apart from reducing emissions, this increases the service life of the filter.

These technologies will help both the environment and the German manufacturer, which can continue to use its ICE-powred cars in the near future, while also expanding the e-tron all-electric range.

 
 
 
 
 

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