Green Power: Low-Emission TDI Engines for the USA

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January 7, 2007

Source: Audi AG

The trend towards diesel engines is becoming ever more pronounced in the United States too. Audi, the inventor of the modern-day TDI, is going on the offensive in an effort to bolster this tendency. 2008 will see the arrival of the Q7 3.0 TDI in US showrooms. Thanks to the exceptionally low emissions resulting from its cutting-edge Bluetec technology, this engine is able to meet even the most stringent emissions limits.

In Europe, diesel-engined cars have been enjoying an inexorable rise in popularity for years now – in Germany, for instance, they accounted for over 45 percent of new car registrations in October 2006. Today’s diesel engines are powerful, fast, efficient, smooth and dependable – virtues which Audi, in its capacity as a pioneer of diesel technology since 1989, has been instrumental in achieving.

The diesel market is also beginning to take off in the USA. In 2006, diesel-powered passenger cars and light trucks secured a market share of around 3.5 percent, and this figure is widely predicted to keep on rising. Firmly convinced that the TDI engine represents the powerful and economical alternative for the future of motoring, Audi is seeking to reinforce this trend: the Ingolstadt brand is embarking on its US diesel initiative.

Strict LEVII standard in California

The stringent legislation governing emissions represents a key criterion for all passenger car engines in the USA. The emission standard entitled US Tier II Bin 8, which is in force in 45 of the 50 US states, limits emissions of nitrogen oxides (NOx) to 0.20 grams per mile and particulate emissions to 0.02 g/mile. The LEVII standard, which is enforced in California and a number of states in the north-east, goes much further again, restricting emissions of nitrogen oxides to 0.07 g/mile and particulates to 0.01 g/mile.

The LEVII limits are simply beyond the capabilities of the emission control technologies required to meet the current Euro 4 standard in Europe. This is why Audi has teamed up with Volkswagen and DaimlerChrysler to develop a revolutionary new technology – it is called Bluetec and denotes exceptionally clean-running diesel engines.

The Bluetec technology is built around a dedicated catalytic converter which goes under the abbreviation of SCR (Selective Catalytic Reduction) and is positioned downstream from the oxidation catalytic converter and the particulate filter. The second system component is an auxiliary tank containing an aqueous carbonyl diamide solution. The solution, which has been labelled “AdBlue”, is injected into the exhaust system in small doses. Once in the hot flow of exhaust gases, it decomposes into ammonia which in turn breaks down the nitrogen oxides into nitrogen and water.

The “AdBlue” reducing agent is routinely topped up at the workshop each time the vehicle is serviced, without the customer having to lift a finger. Audi ensures that there is sufficient “AdBlue” to safely cover the distances between services. Additional benefits include the fact that “AdBlue” is biodegradable and the system’s guaranteed effectiveness for the duration of the vehicle’s service life.

Audi is a driving force behind the advancement of diesel engines

The ultra-clean Bluetec diesel engines see Audi hold true to its tradition of always being at the cutting edge of diesel technology development. The Ingolstadt brand developed direct injection technology back in 1989 – since then, the fuel efficiency of diesel engines has been improved by around 30 percent on average. Compared to 1989 levels, the European emission standard Euro 4 heralds a 93 percent reduction in passenger car particulate emissions; long before the standard came into effect, Audi had already brought out models onto the market which complied with the stipulated limits, even without a particulate filter.

The Audi philosophy has always been to offer customers the best possible solution. And as the only good emissions are those which are not created in the first place, Audi engineers gave top priority to implementing internal engine measures that would further refine the combustion process.

The common-rail technology in the new Audi Q7 V12 TDI with an injection pressure that has now reached the 2,000 bar mark is, for the moment at least, the last link in a long chain of diesel developments.

Others include the four-valve-per-cylinder technology and the accompanying swirl and inlet ports for controlling the airflows, as well as the controlled and cooled system of exhaust gas recirculation; the latter of these innovations is of great importance for the future of diesel engines at Audi.

Higher fuel prices, improved diesel infrastructure

The growing trend towards diesel power which is emerging in the US has been prompted by a number of developments. The sharp increase in energy prices has raised public awareness of the importance of making economical use of resources.

The infrastructure of filling stations stocking diesel fuel for passenger cars is growing, at the same time increasing availability of the low-sulphur diesel fuel (containing less than 50 ppm sulphur) that is one of the fundamental requirements for using Bluetec technology and particulate filters. Irrespective of this, Audi is promoting the development of sophisticated synthetic fuels derived from biomass or natural gas, which by their nature contain considerably fewer pollutants.

The Q7 3.0 TDI will be the first model from Audi to showcase the all-new, ultra-clean Bluetec technology when it is launched in the US in late 2008. Further models are set to follow. And other countries apart from the United States have voiced an interest in the new, extra-green diesel engines, including Japan, China and, not least, the Europeans.

The data and the performance and fuel consumption figures stated here refer to the model range offered for sale in Germany. Subject to amendment; errors and omissions excepted.


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