New GM Truck Diesel Races Emissions Regs - Chevrolet/GMC 6.6L turbochard direct injection diesel V8, Duramax 6600

Automotive Industries, Nov, 1999 by John McCormick

Beginning next fall, General Motors will offer a new 6.6L, direct injection turbocharged diesel V-8 in Chevrolet and GMC heavy-duty (over 8,500 pounds) pickups. Developed in a joint-venture with Isuzu, GM's designated diesel engine experts, the Duramax 6600 has many improvements over the current indirect-injection 6.5L V-8 diesel.

Diesels are steadily capturing the heavy-duty pickup segment. Demand for the oil-burners has climbed from 25% in 1989 to 50% this year. Within a few years the U.S. market for diesel pickups is expected to top 250,000 annually.

Durability, a key consideration in the heavy-duty market, is enhanced on the Duramax by such features as a nitrided crankshaft, induction hardened block and hardened valve seat inserts. But in the quest for weight reduction, the Duramax's cylinder heads will be aluminum -- currently rare in larger diesels.

GM and Isuzu are completing a new facility in Moraine, Ohio, to build the Duramax engines. Though GM will not yet reveal exact power figures for the new engine, engineers admit its output comfortably exceeds that of today's engine, which is rated at 195 hp and 430 lb-ft of torque. Power levels will surpass those of all competitors, claims GM, which means at least 235 hp and 500 lb-ft, the output of Ford's Navistar-built diesel V-8.

The new diesel will be mated to an equally new Allison automatic transmission, an option to the standard six-speed ZF manual. A five-speed, electronically controlled design, the Allison 1000 series features lock-up, overdrive and dual power take-offs. It can handle a maximum of 375 hp and 545 lb-ft of torque. The extra `deep' first gear ratio gives the transmission superior low speed performance, especially when towing, compared to current four-speed automatics, claims GM. Five- and even six-speed automatics are expected to capture the heavy end of the light truck market within a few years, experts say, their extra gear ratios offer higher fuel economy potential.

Though the future for diesel engines looks good in the heavy-duty pickup market, Kerekes admits the outlook could change if emissions legislation becomes an issue. "There is talk of extending light-duty emissions standards up to 14,000 pounds (GVW). If that happens we could be in trouble. Right now there is still a break for 8,500 pounds and above, until 2004."