New Mercedes heavies will be unveiled in 2010

MT has learned that the next-generation Mercedes-Benz heavy-duty diesels will not make their public debut until the IAA show in Hanover in September 2010. The Daimler group's in-line-six HDEP global (heavy-duty engine platform) engines are scheduled to appear in 15.6-litre and 12.8-litre form in Mercedes' revamped heavy truck range - code named SFTP (strategic future truck platform) - set to replace today's Actros and Axor chassis.

The launch will mark the first European HDEP diesel family application, taking over from the 500 Series 12-litre V6, 16-litre V8 and the 12-litre in-line OM457 that power current Actros and Axor chassis. Plans for Mercedes to offer the 14.8-litre version, just launched in the US under the Detroit Diesel banner, are understood to have been shelved. But in April 2011, the smallest HDEP variant, of 10.6-litre capacity, is due to be introduced for lighter SFTP chassis models.

Bernhard Heil, vice-president of Daimler Trucks' powertrain division, explains that Mercedes' move from a 'V' to an in-line engine configuration was driven largely by the needs and related costs of today's emission and fuel-efficiency driven technology. In anticipation of Euro 6 emission limits requiring both SCR and EGR for NOx control, a 'V' layout would have meant much more complex routeing for the recirculated exhaust gas, with a doubling up of the cooling and EGR control componentry.

Similarly, twin turbochargers would have been necessary and a doubling up of the common-rail fuel system installation. Bosch's APCRS stepped-piston-intensified common-rail fuel system sees its first production application in Daimler's new heavy-duty diesels. It generates up to 2,100bar pressure at the injector nozzle from quite modest maximum rail pressure levels of around 850bar.