UPPING THE DIESEL ANTE.(Mercedes-Benz E-Class)

Byline: Roger Hart

The C-Class cars aren't the only Mercedes vehicles scheduled to get a new powerplant. The E320 CDI that went on sale here last year (AW, May 3, 2004), powered by a 3.2-liter turbodiesel inline six, will be fitted next year with a new aluminum, turbocharged 3.2-liter V6. Mercedes claims a world's first in offering a diesel engine with an aluminum crankcase and cast-in grey iron cylinders. Aluminum is also used for the cylinder heads and other engine components, such as the water pump, oil sump and pistons.

Metallurgical magic aside, improvement is down to the third generation of Mercedes CDI (Common-rail Direct Injection) technology. The engine makes 221 hp at 3800 rpm and 376 lb-ft of torque from 1600 to 2800 rpm. The old inline six made 201 hp at 4200 rpm and 369 lb-ft at 1800 to 2600 rpm.

Like its predecessor, the V6 diesel is outfitted with a variable nozzle turbine turbocharger that reacts quickly to changes in engine revs by electrically adjusting the pitch of the guide vanes based on engine speed. An intercooler reduces the temperature of the compressed air, further enhancing performance.

Our first sampling of this engine was in a C-Class fitted with the seven-speed automatic found in the gas-powered cars. (There are no plans to bring a diesel-powered C-Class to the States.) Mercedes claims 0 to 62 mph takes just 6.9 seconds, less than a second slower than its gas ...