For the 2006 model year, the Duramax LLY underwent many changes and enhancements to increase both performance and strength. Though not explicitly stated by General Motors, it is believed that these upgrades were necessary in order to maintain reliability and longevity, not only in terms of the horsepower and torque improvements of this model year, but to endure future evolutions of the engine platform. The general specifications and engine architecture remained unaltered with respect to this changes.
• New cylinder block casting and machining procedure designed for higher strength.
• Main bearing material updated for increased longevity and bottom end reliability.
• Compression ratio lowered from 17.5 to 16.8:1.
• New piston with larger piston pin diameter.
• Revised cylinder head design (matching lowered compression ratio).
• New, thicker connecting rod design.
• Maximum fuel pressure increased from 23,000 to 26,000 psi resulting from new high pressure fuel pump assembly.
• Revised, 7 hole injector design and positioning. New injectors spray directly onto the glow plug tip in order to provide quicker/easier starts and reduce emissions output during start-up.
• New "fast heat" glow plugs.
• Upgraded variable geometry turbocharger (VGT) for lower emissions, improved efficiency, and all-around general performance.
• Revised air induction system to reduce engine noise.
• Larger exhaust gas recirculation (EGR) cooler.
• Intake air heater introduced in order to reduce emissions while engine is cold and allow engine to reach operating temperature quicker.
As a result of these changes, the engine horsepower rating remained at 310 hp @ 3,000 rpm while the engine torque rating was increased from 520 lb-ft @ 1,600 rpm to 605 lb-ft @ 1,600 rpm - a significant 85 lb-ft gain.