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Old 11-30-2010, 09:20 PM
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Default Brief History of the Duramax

In 1998 General Motors (GMC/Chevrolet) began a joint venture with Isuzu in manufacturing a new version of diesel engines for its trucks, vans and SUVs. In 2001, the new diesel engine --- the Duramax --- was released for sale. The Duramax began its life during a tough time for diesel engines, as the Environmental Protection Agency (EPA) had begun more strictly regulating diesel engines. Partly due to the EPAs ever-changing laws, the Duramax has endured five generational changes since 2001: LB7, LLY, LBZ, LMM and LML.

  1. LB7 The LB7 --- the first Duramax engine --- hit the market in 2001 and lasted until 2004. This engine had a bore --- cylinder width --- of 4.06 inches, a stroke --- distance piston travels inside the cylinder --- of 3.90 inches and a compression ratio of 17.5:1. It had an overall displacement of 403 cubic inches, or 6.6L. This engine produced 235 horsepower at 2,700 rpm to 300 horsepower at 3,100 rpm and 500 foot-pounds of torque at 1,600 rpm to 520 ft-lb of torque at 1,800 rpm.
  2. LLY The second Duramax engine --- the LLY --- first appeared in 2004, when GM needed to add emission controls to meet upcoming requirements. This engine had mostly the same internal mechanics as the LB7: 4.06-inch bore, 3.90-inch stroke and 403 cubic inches of displacement. The compression ratio also remained the same, at 17.5:1, until 2006, when it dropped to 16.8:1. This engine produced 310 to 320 horsepower at 3,000 rpm and 520 to 560 ft-lb of torque at 1,600 rpm. The LLY Duramax lasted until late-2006.
  3. LBZ The third generation of Duramax engines --- the LBZ --- saw its first use in late-2006. This engine shared mechanical structure with the LLY, but had a more tuned electronic system that led to higher output. The bore of 4.06 inches, stroke of 3.90 inches, 16.8:1 compression and 403 cubic inch displacement all carried over from the LLY. This engine produced 360 horsepower at 3,200 rpm and 650 ft-lb of torque at 1,600 rpm. This engine was replaced after the 2007 model-year due to future emissions restrictions.
  4. LMM In mid-2007, GM released the fourth generation of Duramax diesels --- the LMM --- to meet upcoming emission regulations. This engine, again, had the same internals as its predecessor: bore of 4.06 inches, stroke of 3.90 inches, 16.8:1 compression and 403 cubic inch displacement. The LMM-model of the Duramax had slightly improved performance numbers to go along with the new emission controls, 365 horsepower at 3,100 rpm and 660 ft-lb of torque at 1,800 rpm. As of 2010, the LMM is still used by General Motors.
  5. LML The LML Duramax --- the fifth generation --- is fitted into 2011 model-year GM trucks, vans and SUVs. This engine meets all emission regulations in the foreseeable future and has significant power increases over the previous years. It produces 397 horsepower at 3,000 rpm and 765 ft-lb of torque at 1,600 rpm, making it the cleanest running and most powerful Duramax to date. The internals are again carried over from the previous Duramax engines: bore of 4.06 inches, stroke of 3.90 inches, 16.8:1 compression and 403 cubic inch displacement.

Read more: GM Diesel Specifications |
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Last edited by stodg73; 09-18-2012 at 08:26 PM.
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