General Motors reported two diesel engines for the Chevrolet and GMC three-quarter ton pickup trucks for 2011 that also included the off road Z71 performance option. The Duramax turbo-diesel V8 has an output of 397 horsepower at 3,000 rpm and maximum torque of 765 lb-ft at 1,600 rpm. The Silverado HD, along with the cab-only chassis models, is offered with a 6.6-liter V8 that is rated at a lower 335 horsepower and 685 lb-ft of twisting torque.
The 6.6-liter Duramax turbo-diesel first became available in 2001 and production ran unchanged until 2004. The 403-cubic-inch 32-valve aluminum heads with a cast-iron block and four bolt mains used the high pressure (23,000 psi injection pressure) direct injection common rail fuel delivery system. This V8 was a 90-degree design with a bore of 4.06 inches, stroked to 3.90 inches, with a 17.5:1 compression ratio, and weighed out at 835 lbs. Its output in 2001 was 235 horsepower at 2,700 rpm with 500 lb-ft torque at 1,600 rpm, that increased by 2004 to 300 horsepower at 3,100 rpm with 520 lb-ft torque at 1,800 rpm. The engine red-line rpm was 3,250 rpm.
The second generation of Duramax 6.6-liter turbo-diesels was announced in 2004 to replace the LB7. This was General Motors’ initial attempt at emission controls for a diesel engine, and utilized a variable geometry turbocharger combined with an exhaust gasses recirculation (EGR) system. The engine was basically the same, with a higher reporting of 310 horsepower at 3,000 rpm combined with 520 lb-ft torque at 1,600 rpm. In 2006 GM reported an increase to 320 horsepower and 560 lb-ft of torque at the same rpm, even though the compression ratio dropped to 16.8:1.
The LBZ computer-controlled 6.6-liter turbo-diesel replaced the LLY in late 2006. The engine’s basic configuration remained unchanged. Added was the Bosch direct injection CP3 fuel pump fuel delivery system, which was now exhaling through a Catalytic converter to meet the more strict emission controls. The new engine reported an output of 360 horsepower at 3,200 rpm, and 650 lb-ft torque at the low rpm of 1,600.
The LMM was almost identical to the LBZ it replaced in 2007. Its main features were a higher pressure (26,000 psi) Bosch CP3 common rail fuel delivery system, and also added a diesel particulate filter (DPF) for cleaner burning. The new LMM was reported to have increased horsepower to 365 at 3,100 rpm, and 660 lb-ft at a higher 1,800 rpm, with the engine red line being higher at 3,400 rpm.
The fourth generation of Duramax diesel was designated the LML. The engine was still basically the same configuration but with a 30,000 psi Bosch common rail fuel delivery system now with Piezo injectors, diesel exhaust fluid injection, which allows the new engine to exceed government diesel emission standards. The newly reworked engine was now able to burn B20 bio-diesel which bumped the horsepower up to 397 horsepower at 3,000 rpm and a low end twisting torque of 765 lb-ft at the low 1,600 rpm.