According to Automotive News Europe, Volkswagen group will switch completely to common-rail technology when it launches a new generation of three- and four-cylinder diesel engines starting in 2007.

The German automaker is dropping its unit-injector fuel management system. VW decided it would be too difficult to adapt the system, which it calls Pumpe-DŸse, to work with particulate filters, which must be added to diesel systems so they can meet tougher European Union emission laws due to take effect before the end of the decade.

When it was introduced in 1998, VW's unit-injector 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 unit-injector systems have lost their technological edge over common-rail fuel-injection systems.

VW uses common-rail systems on its models with V6 and V8 diesel engines.

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

Robert Bosch supplies 1.8 million unit-injector systems a year to VW, its only customer for the technology that it developed. A Bosch spokesman said the company is in talks with VW to supply the carmaker with Bosch common-rail systems to replace the unit-injector technology. Bosch supplied 5.8 million common-rail systems in 2004 and 25 million since 1997. One of its customers is VW subsidiary Audi.

Last November VW opened a EUR240m joint venture plant in Stollberg, eastern Germany, with Siemens VDO Automotive to manufacture injectors for unit-injector systems. A VW source said the plant could be used to produce other parts, likely common-rail system components.