VW adopts common-rail fuel injection

The Volkswagen group will switch to common-rail diesel technology when it launches a new generation of three- and four-cylinder diesel engines starting in 2007.

VW is dropping its Pumpe-Duese, or pump nozzle, fuel management system. VW decided it would be too difficult to adapt it to work with new particulate filters needed to meet tougher emission laws planned by the European Union.

When it was introduced in 1998, VW's pump-injection system was touted as a revolutionary technology that made diesel engines quieter, more powerful and more efficient than engines with traditional fuel-injection systems.

But Pumpe-Duese has lost its technological edge over common-rail fuel injection systems.

The latest common-rail systems are cheaper to make than Pumpe-Duese. They also run more quietly and can handle the injection cycle demanded by diesel particulate filters much better than Pumpe-Duese systems.

In November 2004, VW and Siemens VDO Automotive opened a joint-venture plant in Stollberg, Germany, to manufacture injectors for Pumpe-Duese systems. The plant cost 240 million euros, or about $291.3 million at current exchange rates.

A VW source said the plant could be used to produce other parts, likely common-rail system components. Siemens VDO supplies piezo-actuated injectors for common-rail systems.

In a Pumpe-Duese engine, a pump injector at each cylinder produces a fine spray of diesel fuel for more efficient fuel combustion. Common-rail technology uses one pump and a common rail through which pressurized diesel fuel is delivered to each cylinder.

Pumpe-Duese will not work with the advanced particulate filters that will be needed to meet stricter emissions rules. Those particulate filters need multiphase injections of diesel fuel, including pre- and post-injections. Because Pumpe-Duese injects individual cylinders, it cannot produce pre- and post-injections.

Common-rail systems, which operate with a continuous pressure, are more flexible, and injections can be triggered at any time.

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