Volkswagen has unveiled what it claims is the cleanest-ever TDI engine.
Based on a normal 2.0-litre common-rail four-cylinder diesel unit, the new engine uses a special catalytic converter to reduce nitrogen oxide (NOx) emissions by up to 90 per cent.
A nitrogen oxide reservoir in the catalytic converter prevents much of the harmful gas venting into the atmosphere, allowing the new engine to comply with tough Californian emission standards. Though currently still under development, the new engine will go into production in the US in 2008.
In a similar manner to some existing particulate filters on diesel engines, VW's system allows a build-up of NOx, before automatically cleaning itself. It will be used on VW's smaller cars – anything below the Passat. Larger VWs will use the BlueTec system revealed late in 2006 as a joint project between VW, Audi and DaimlerChrysler, which uses an additive to separate NOx into nitrogen and water.
There's no word yet on whether or not we'll get the cleaner diesels in Europe.