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Running Clean

GM says it has a diesel engine that is 50-state legal

General Motors powertrain engineers unveiled a V8 diesel available for light-duty trucks after 2009 that they say meets the ultra-strict 2009 federal emission standards.

To date, only Mercedes-Benz and, most recently, Honda have said they will introduce new diesels that will meet the standards. In 2009, federal emission laws will coincide with California's standards in which gasoline and diesels must meet the same guidelines—the so-called Tier 2 Bin 5 and LEV 2 standards.

"It will be compliant in all 50 states," said Tom Stephens, group vice president for GM Powertrain, about the company's new V8 diesel.

GM announced the new diesel at a technology show at its Milford, Michigan, proving grounds in late August. While not allowing members of the media to see the engine, journalists were able to drive a Buick Rainier test mule powered by it.

Specifics were limited, because of patent applications in process, but this much we do know: The V8 block, made of compacted graphite iron with an aluminum head, displaces "more than 3.0 liters but less than 6.6 liters," is turbocharged and intercooled, fits the same profile as a small-block V8 gas engine, and is a dual-overhead cam, four-valve design that uses liquid urea injected into the exhaust system along with filters to clean up the emissions.

Horsepower of the engine we drove was 330 with 520 lb-ft of torque. Peak power was at 1800 rpm.

The engine was strong off the line, although in our first attempt to drive the vehicle, there was a problem with the exhaust system that limited power. We were invited back several days later, and things worked properly. At 60 mph in the Rainier, the engine turned a very smooth 1600 rpm. At idle, the diesel was gas-engine quiet, but there is induction noise at the hit of the throttle.

Charlie Freese, executive director of GM's diesel engineering unit, would not say how much pressure the common-rail fuel system was running, but the engine uses at least five fuel injections per cycle to control noise and emissions.

In announcing the new engine, Stephens said diesels will play an increasing role in propelling future GM models, along with traditional gasoline engines, flex-fuel engines, gas-electric hybrids and hydrogen fuel cells.

"There is no silver bullet here," he said. In other words, the company isn't putting all its efforts into one technology.

GM sells more than 1 million diesel engines annually in 17 variants around the world. In the United States, GM now sells only a 6.6-liter V8 Duramax used in heavy-duty trucks.

Solving the emissions problems inherent in diesel engines—namely soot (particulates) and oxides of nitrogen—would make this engine a candidate for a variety of applications. With a 25 percent gain in fuel economy over similar-sized gas engines, the diesel unit would be welcome in pickups and SUVs but could also find installation in large sedans.

More than once, Freese and Stephens referred to the diesel as a "premium" product, so we wouldn't be surprised to find it in a large Cadillac sedan or crossover, as well as in pickups and sport/utes.

"This is game-changing," Freese said.

You may e-mail Roger Hart at rhart@crain.com

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