General Motors Corp.’s revolutionary new 4.5L V-8 Duramax turbo-diesel, which makes its debut in Chevrolet Silverado and GMC Sierra light duty trucks in the 2010 model year, is compact, powerful and fuel-efficient. The engine also is lighter, an important consideration in the competitive light truck market, because it was designed with more than 70 fewer parts.

The new dual-overhead cam, four-valve V-8 diesel engine boasts a number of innovative design approaches that have enabled its compact size and mass, including integral aluminum cylinder head exhaust manifolds, integral cam cover intake manifolds and a narrow V-angle block. The new V-8’s compact size enables it to fit within the same space of a small-block V-8 gasoline engine and offers GM the flexibility to introduce it in a wide variety of vehicles to meet market demand.

The new 4.5L V-8 diesel is expected to deliver more than 310 horsepower (231 kW) and 520 lb-ft of torque (705 Nm), while delivering a 25-percent engine fuel efficiency improvement versus comparable gasoline engines.

“This premium diesel engine is expected to deliver the power, torque and refinement our customers expect,” said Tom Stephens, executive vice president, GM Global Powertrain and Global Quality.

The new V-8 diesel will be GM’s first engine to use a selective catalytic reduction (SCR) NOx after-treatment system with a diesel particulate filter to help achieve Tier 2 Bin 5 and LEV 2 emissions, making it compliant in all 50 states. SCR was chosen for its proven NOx reduction capability and durability, and high efficiency while operating in optimal diesel combustion modes, making it a very attractive system to achieve high fuel economy.

The environmental benefits of the new engine include a 13-percent reduction in CO2 emissions and at least a 90-percent reduction in particulates and NOx compared to many diesel vehicles today.

Technical highlights

Robust and innovative, the new 4.5L diesel V-8’s technical details include lightweight aluminum cylinder heads with integrated manifolding; a variable-vane turbocharger with intercooling; a compacted graphite iron (CGI) cylinder block for a stronger and lighter base engine (compared to lower-strength aluminum or heavier grey cast iron); and a fracture-split main bearing cap system. GM has applied for patents on a number of these features and expects to have several patents granted before the engine launches.

Compared to typical production diesel engines, GM’s new 4.5L V-8 turbo-diesel innovatively reverses the flow of air and exhaust gases entering and exiting the cylinder heads. Air enters the engine through ports in the top portion of each cylinder head. Exhaust gases exit inward between the cylinder heads and directly into a turbocharger.

“By using integral cylinder head exhaust manifolds, integral cam cover intake manifolds and a narrow cylinder block, designers saved space and reduced the engine’s weight. And because the engine makes more efficient use of heat, fuel economy and performance are enhanced, and noise and emissions are reduced,” said Gary Arvan, chief engineer for the 4.5L V-8 diesel.

An electronically controlled, 29,000-psi (2,000 bar) common-rail fuel system is also used on the engine. It has the ability to inject fuel five times per combustion event, reducing noise and emissions while enhancing fuel economy.

“This new V-8 diesel meets the toughest emissions requirements in North America, and it also delivers an effortless performance feel because of its high torque across the speed range,” said Charlie Freese, executive director of GM Powertrain Diesel Engineering. “It is also significantly quieter than many other diesels on the road today, with noise and vibration performance approaching gasoline V-8 levels.”

GM’s global diesel offerings

GM (Opel, Saab, Vauxhall and GMDAT) currently offers 16 diesel engine variants in 45 vehicle lines around the world. GM sells more than one million diesel engines annually, with products that offer a range of choices, from the 1.3L four-cylinder diesel engine found in the Opel Agila and Corsa, to the 6.6L V-8 Duramax diesel offered in full-size vans, heavy-duty pickups and medium-duty trucks in the United States.

GM introduced the Duramax diesel 6.6L V-8 in North America in the 2001 model year. Since then, customer enthusiasm for it has helped GM’s heavy-duty pickup market share jump nearly tenfold in the seven years the Duramax has been offered.

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