New 6.6L Duramax Turbodiesel for Silverado Offers More Power, Lower Fuel Consumption and Lower Emissions
15 February 2010
| 2011 Duramax 6.6L V8 Turbo with 2011 Allison 1000 6-Speed Automatic for Silverado HD. Click to enlarge. |
GM is introducing a new Duramax 6.6-liter turbodiesel V8 on the Chevrolet Silverado 2500HD and 3500HD launching this summer. The new engine offers significantly more torque and higher horsepower ratings (yet to be released), along with improved fuel efficiency, B20 biodiesel capability, and an SCR aftertreatment system that reduces NOx emissions reduced by at least 63%, compared to the 2010 model. The new Duramax turbodiesel delivers up to 11% greater highway fuel economy than the outgoing vehicle.
The original Duramax turbodiesel featured first-in-class common rail fuel injection and aluminum heads with a six-bolt-per-cylinder design. Those attributes formed the foundation for the 2011 engine, with digital modeling and simulation tools used to raise the Duramax’s power and durability benchmarks. The internal elements that help enhance strength and durability include:
The main bearing profiles are changed to enhance oil film thickness
Oil pump flow is increased for more pressure at low speeds
The turbocharger’s oil circuit is changed to provide increased pressure at the turbo and faster oil delivery
The connecting rods’ pin ends are modified to provide increased piston support
A new, higher-strength piston design eliminates bushings to provide lower reciprocating weight
An EGR cooler bypass reduces high-mileage soot deposits in the cooler and EGR circuit
The new Duramax 6.6L improves on an already low-noise reputation with double-pilot injection, a strengthened block and, in some conditions, lower rail pressure, contributing to a nearly 30% improvement in noise at the engine level. A new 30,000-psi (2,000 bar) piezo-actuated fuel injection system—capable of operating on ASTM grade B20 biodiesel—ensures more precise fuel delivery, improving emission performance and playing a crucial role in reducing high-speed noise, vibration and harshness.
The new Duramax 6.6L helps boosts towing capacity of the Silverado HD trucks to a maximum of 20,000 pounds (9,072 kg), which is best in class. Power and cooling improvements, along with improvements to the truck chassis, were key elements in boosting the towing rating.
In addition to the SCR aftertreatment system, the 2011 Duramax 6.6L will also include GM’s second-generation diesel particulate filter system. Unlike most of the competition, the Duramax regenerates its diesel particulate filter using a downstream injection of diesel fuel directly into the exhaust stream and can travel up to 700 miles (1,125 km) between regenerations—a 300-mile (482 km) increase over the previous Duramax engine. The use of downstream injection also helps to improve engine life by eliminating concerns surrounding the possibility of diesel fuel contaminating engine oil, which can happen when fuel used for regeneration is introduced directly into the cylinder.
A new feature on Duramax-equipped Silverado models is an exhaust brake system. This driver-selectable feature uses the turbine control of the variable geometry turbocharger and the compression of the engine to generate backpressure, slowing the vehicle without applying the brakes. It is a smart system integrated with the cruise control feature and varies the braking to account for the grade and vehicle load.
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