Pollutant Emissions

To ensure sustainable road-based mobility, it is necessary not just to reduce CO2 emissions but also to reduce emissions of pollutants such as diesel particulates and nitrogen oxides. This requires continuous improvement of our engine technologies, focusing particularly on optimised combustion processes. It also requires the use of downstream emission control systems. Throughout the Group, we offer diesel particulate filters either as standard or optional equipment for almost all new TDI-engined vehicles. These filters have been long-term-tested and in all cases are specially developed and matched to the requirements of the individual vehicle and its engine. For older vehicles, we also offer a wide range of retrofit solutions.

Diesel particulate filter for the Golf V

Clean stuff
In mid-2008, the Volkswagen Group will start production of "Clean TDI" models equipped with the world's cleanest diesel technology. The new engines will combine the lively performance and superior pulling power of the current TDI engines with excellent fuel consumption and unsurpassed low emissions output. The integrated downstream "ultra low emission system" then eliminates most emissions from the exhaust stream.

Optimised combustion and integrated emissions control
The overall system, combining engine-based measures with new downstream treatment technologies, is highly effective in reducing nitrogen oxides. The engine itself is based on the TDI principle, combining diesel direct injection with turbocharging, to which it adds a whole range of innovative features: together, the new piezoelectric common rail injection system, developing maximum injection pressures of 2000 bar, the highly efficient exhaust gas recirculation system and optimised turbocharging sharply reduce engine-out emissions. The combustion chamber sensors – a world-first system – result in even more precise control of the combustion processes.

The finishing touches are provided by the downstream ultra low emission system, consisting of a catalytic converter, metering module, AdBlue tank, heated lines and a comprehensive sensor system. With a NOx adsorber catalyst, or SCR (Selective Catalytic Reduction) catalyst on the larger models, the system reduces nitrogen oxide emissions by up to 90 percent.

The SCR catalyst in the ultra low emission system operates with AdBlue, a biodegradable urea solution which is injected in tiny doses upstream of the catalyst. On entering the hot exhaust stream, the urea is converted into ammonia, which then reduces the nitrogen oxides into nitrogen and water. The system comprises a catalytic converter, metering module, AdBlue tank, heated lines and a comprehensive sensor system. The extensive downstream emission control system is completed by an oxidation catalyst and a highly efficient controlled diesel particulate filter.

With their optimised combustion process and ultra low emission system, these vehicles meet the US BIN 5 standard and future very stringent European standards. They can be used anywhere in the world, since they meet even the very strict regulations in the US state of California. The Clean TDI offers fuel economy up to 35 percent better than the average for conventional petrol engines in the US fleet as a whole.

Cooperation against nitrogen oxides
In the US, the Volkswagen and Audi brands have launched the BLUETEC initiative, in association with Mercedes-Benz. The aim of this partnership is to establish the BLUETEC label as a badge for clean and fuel-efficient diesel cars and to further reduce emissions, particularly of nitrogen oxides (NOx). Our diesel engines will in future meet the strictest emissions standards in the US market, and in terms of fuel economy will also offer an alternative to hybrid drive.