6.6L Duramax L5P

6.6L Duramax L5P Specs, Ratings, & Information

General Motors' highly anticipated reveal of the next generation Duramax diesel was momentarily interrupted by inadvertently publishing details of the engine's 2017 model year horsepower and torque figures via GM's Powertrain division website. Full details of the Duramax L5P shortly followed, outlining the various improvements and upgrades that help it produce 445 horsepower and 910 lb-ft of torque in addition to handling the rigorous conditions experienced under such loads. Although the L5P measures in at 6.6 liters of displacement (utilizing the same cylinder bore and stroke as previous generations), it's not far off from being characteristically classified as a clean slate design. The Duramax L5P replaced the outgoing LML for the 2017 model year Chevrolet Silverado and GMC Sierra HD pickups.

The time leading up to the introduction of the L5P had been chalked full or rumors and speculation regarding the new Duramax, which some insisted would require clean slate revisions and an increase in displacement to reach the segment's leaders. The rumors were put to rest when the 6.6L Duramax L5P was officially released, producing 48 horsepower and 145 lb-ft of torque more than the outgoing LML. A notable revision of the fuel system resulted in the advent of electronically actuated solenoid injectors instead of the piezo electric injectors the Duramax engine platform had used since its inception in 2001.

6.6L Duramax L5P Specs


6.6L Duramax L5P, 90° V-8 diesel

Assembly Location:

DMAX assembly plant in Moraine, Ohio

Years Produced:

2017 - current

VIN Code:



403 cubic inches (402.62 CID), 6.6 liters (6599 CC)

Head/Block Material:

Aluminum cylinder heads, cast iron engine block w/ induction hardened cylinder walls

Compression Ratio:

16.0 : 1

Firing Order:



4.055" (103 mm)


3.897" (99 mm)


Electronically controlled and actuated variable geometry turbocharger, air-to-air intercooler


Direct injection, 29,000 psi high pressure common rail, solenoid injectors delivering up to 7 injection events per combustion sequence


OHV (overhead valve), 4 valves per cylinder (32 valve), mechanical roller lifters

Rotating Assembly:

Cast nodular iron main bearing caps, forged steel crankshaft, steel camshaft, powered metal connector rods

Oil Capacity:

10 qts w/ filter

Cooling System Capacity:

31.4 qts

DEF Capacity:

7.0 gallons

Fuel Compatibility:

Ultra low sulfur diesel (ULSD) or max B20 biodiesel blend

Max Engine Speed:

3,450 rpm

Peak Horsepower:

445 hp @ 2,800 rpm

Peak Torque:

910 lb-ft @ 1,600 rpm








Duramax L5P Changes, Improvements, & Revisions

Although the Duramax remains at 6.6 liters of displacement, it's only a distant relative of past generations. The L5P's electronic and structural design features are more sophisticated and robust than ever before. Contributing to the L5P's increase in power as well as ensuring survival under greater engine loads are the following changes and improvements:

• Strengthened cylinder block - new casting and induction hardened cylinder wall. New engine block features 5 nodular iron main bearings and 4 bolt, cross bolted main bearing caps.

• More robust rotating and reciprocating assemblies - this includes a larger diameter crankshaft with larger connecting rod journals and a increased bearing surface area, fractured cap forged and sintered powdered metal alloy connecting rods, cast aluminum "remelted" pistons (bowl rim of piston crown is reheated after being cast in order to reduce grain size and create a more consistent grain structure).

• New camshaft design with enhanced cam profile.

• Electronically controlled and actuated variable geometry turbocharger, maximum boost pressure increased to ~ 28 psi manifold gauge pressure. The turbocharger design is said to provide more effective, more efficient exhaust braking through enhanced VGT control.

• Upgraded single-cooler exhaust gas recirculation (EGR) system, integrated throttle valve introduced to regulate intake manifold pressure and EGR flowrate.

• Increased oil and engine coolant flowrates. Piston cooling jets flow 50% more than outgoing Duramax LML, and the revised oil passage design features a dedicated turbocharger oil supply line. A high capacity engine oil cooler provides up to 50% greater oil cooling than outgoing LML.

• Improved fuel system and fuel injector design.

• Two piece oil pan - the top portion of the oil pan is produced from cast aluminum, while the lower section is laminated steel. The cast aluminum top section acts as an engine block girdle, increasing strength and overall rigidity. GM claims the laminated steel section was added as a noise suppressant, as aluminum has a tendency to resonate engine harmonics.

• More efficient (enhanced airflow) cylinder head casting with layered coolant passages for greater rigidity and overall cylinder head strength.

• Improved ceramic glow plugs - designed to reduce glow plug preheat times. New glow plug control system features a temperature compensation attribute which can adjust current flow to each individual glow plug to maintain consistent temperature cylinder-to-cylinder during cold starts.

• Allison 1000 automatic transmission returns with several upgrades, including a new torque converter.

• New air intake system featuring a functional hood scoop.

2017 GMC Sierra hood scoop, standard on the Duramax diesel

Functional hood scoop on the Duramax L5P equipped, 2017 model year
GMC Sierra HD and Chevrolet Silverado HD

L5P equipped trucks feature a unique, functional hood scoop integrated alongside a standard air intake system. According to GM, 60% of the engine's incoming air is provided through the hood scoop while 40% is furnished by a traditional intake system that draws air from one of the front fenders. In additional to providing a cooler air intake charge, the hood scoop provides a ram air effect at cruising speeds, reducing turbocharger lag and improving overall engine performance while the vehicle is in motion. The hood scoop system includes an air-water separation chamber that GM claims keeps the incoming air charge dry regardless of ambient conditions. The L5P's intake system is a patent pending design.

Duramax L5P Horsepower & Torque Curve

6.6L Duramax L5P horsepower and torque curve

For 2017, the Duramax L5P produces 910 lb-ft of torque at 1,600 rpm and 445 hp @ 2,800 rpm.
This is a 19% improvement in torque and 12% improvement in horsepower over the retired LML.