Audi Announces Plans for Cleanest Diesels in the World

In mid-2008, Audi will introduce what it is calling the cleanest diesel engines in the world, thanks to its turbocharged direct-injection (TDI) technology. The first of these power plants will appear in a three-liter V6 for the Audi A4 and Q7. Additional models will follow in fast succession. Audi expects to extend the new technology to other vehicle classes and power categories by 2010.
While turbocharged direct injection certainly isn't new, Audi is introducing several innovations. The new engines will have piezoelectric common rail systems that deliver an injection pressure of 2,000 bar. They will also feature a more efficient exhaust gas recirculation system, which should bring a dramatic cut in untreated engine emissions, according to company officials. The motors will likewise feature combustion chamber sensors that enable a more precise regulation of the combustion cycle. The new TDI engines feature a "downstream ultra-low emission system," which reduces nitrogen oxide emissions by up to 90 percent. It operates on a biodegradable additive in the form of a solution called AdBlue. Tiny doses of this solution are injected upstream from the DeNOx catalytic converter. The ultra-low emission system as a whole comprises the catalytic converter, the metering module, the AdBlue tank and heated lines, as well as an extensive system of sensors. The engines will also include a separate two-way catalytic converter and an electronically controlled diesel particulate filter.