6.6L Duramax L5P horsepower and torque curves, 445 hp @ 2,800 rpm, 910 lb-ft @ 1,600 rpm 6.6 Duramax L5P Changes, Upgrades, & Improvements Although the displacement of the Duramax diesel remains unchanged, it represents a distant relative of past generations of the Duramax 6600 engine fam...