PHOENIX, Arizona - General Motors Corp. plans to make a heavy duty impact in the heavy duty pickup market this fall when it luanches an all-new V-8 turbodiesel engine as an option for its 2001-model Chevrolet Silverado and GMC Sierra three-quarter-ton and 1-ton "work" pickups.

The new 6.6L turbodiesel engine - dubbed Duramax - was developed by GM and Isuzu Motors Ltd. through their joint venture, DMAX Ltd. The engine will be built at the new DMAX production site in Morain, OH, which built the previous-generation GM 6.5L work-truck diesel.

GM's outgoing 6.5L turbodiesel - which dates to 1982 - no longer was competitive against newer work-pickup diesel engines offered by Ford Motor Co. (International-made) and DaimlerChrysler Corp. (made by Cummins Engine Co.).

Now GM believes the launch of the 6.6L Duramax V-8 will drastically change its fortunes in the heavy duty pickup market, traditionally a bastion of hard-core truck customers - genuine diesel engine enthusiasts.

"We fully expect to win market share from Ford and DaimlerChrysler with this new diesel," says one GM source.

When launched this fall, the Duramax easily will top its competitors in the all-important measures of power and torque: it produces 300 hp at 3,100 rpm and a trailer-yanking 520 lb.-ft. (705 Nm) of torque at 1,800 rpm. By comparison, Ford's 7.3L turbodiesel produces just 235 hp - its 500 lb.-ft. (678 Nm) of torque comes close to the new Duramax - and DC's Cummins-made 5.9L turbodiesel produces 235 hp and 460 lb.-ft. (624 Nm) of torque.

Accompanying the Duramax will be an all-new 5-speed automatic transmission developed by GM's Allison Transmission division. A new-for-GM 6-speed manual transmission (developed and built by ZF Friedrichshafen AG) is available, but GM expects 90% of its Silverado/Sierra 2500/3500 series trucks to be ordered with the Allison automatic.

The Duramax follows the industry standard architecture of pushrod-activated valves, but has four valves per cylinder; the Ford diesel makes due with just two valves. The Duramax also includes a host of other contemporary diesel features, including direct injection (with multiple injection phases) and common-rail fueling. GM engineers say another advantage is the engine's physical size, both shorter and narrower than the competition's V-8 diesels.

"We've targeted best-in-class goals for virtually everything," says one GM engineer of the Duramax, noting, in particular, GM's lofty noise, vibration and harshness (NVH) targets.