Heavily Revised 6.6L Duramax brings 910 lb-ft. to the table. Wayne Gerdes – CleanMPG – Sept. 29, 2016 2017 6.6L Duramax in the 2017 Chevrolet Silverado and GMC Sierra HD – More power. Efficiency? To Be Determined. Dallas, Texas -- At the Texas State Fair this week, Chevrolet introduced its answer to the all-new 2017 Ford Super Duty and its own super powerful, in-house designed and built 6.7L Power Stroke. What it brought to the game was a redesigned 445 hp and 910 lb.-ft of torque – 90 percent of that available from just 1,550 rpm - 6.6L Duramax turbo diesel. GM also stated this new engine idles as much as 38 percent quieter than the previous Duramax. The publicly released list of revisions and updates looks like this: Stronger block, heads, rotating and reciprocating assembly, increased oil- and coolant-flow cap, updated EGR with a single cooler and integrated bypass, electrically actuated/controlled turbocharger, new solenoids, electronic controls, full-length damped steel oil pan, rocker cover/fuel system acoustical treatments and B20 capability. All of these updates provide owners with a vehicle that can maintain its full capability in worse conditions. From the outside of the 2017 Silverado HD you can see the new hood with an air intake slot. The Block, Crank and Pistons The new Duramax block is cast-iron with induction-hardened cylinder walls and five nodular <-- I have no idea what that is - iron main bearings. It retains the same 4.05” and 3.89” bore and stroke as the current engine. A die-cast aluminum lower crankcase strengthens the engine block and serves as the lower engine cover, while reducing its overall weight. Larger diameter crankshaft connecting rod journals with increased bearing area and stronger crankshaft can handle the higher expected loads. An enhanced oiling circuit, with higher flow capacity and a dedicated feed for the turbocharger, provides increased pressure at the turbo and faster oil delivery. Larger piston-cooling oil jets at the bottom of the cylinder spray up to twice the amount of engine oil into oil galleries under the crown of the pistons, contributing to lower engine temperature and greater durability. The new oil cooler provides 50 percent more oil capacity. The new two-piece laminated steel oil pan uses an upper aluminum section and reduces noise. A forged micro-alloy steel crankshaft with cut-then-rolled journal fillets contribute to the new engines durability. The connecting rods are also stronger with new 45-degree split-angle design. A new, stronger cast-aluminum piston features a taller crown area and a remelted combustion bowl rim for greater strength. Remelting is an additional manufacturing process for aluminum pistons in which the bowl rim area is reheated after casting and pre-machining, creating a much finer and more consistent metal grain structure that enhances their thermal fatigue properties. New Heads, Injectors, Turbo and EGR The aluminum cylinder heads incorporate six head bolts and 4 valves/cyl. A new double-layer water core design separates water cores in layers to create a stiffer head structure with more precise coolant flow. The heads’ airflow passages enhance airflow. Solenoid-type injectors at 29,000 psi create a cleaner burn that reduces particulate. The new injectors can inject up to seven times per combustion event, contributing to lower noise, greater efficiency and lower emissions. The less-complex solenoid injectors are said to deliver comparable performance to the more advanced piezo injectors. The new electronically controlled, variable-vane turbocharger produces higher maximum boost pressure — 28 psi — increasing power and adding stronger exhaust-brake capability. The new variable-vane turbocharger enables the engine to deliver more power with lower emissions by allowing a 104-degree F increase in exhaust temperature capability. The self-contained mechanism decouples movement from the turbine housing, allowing operation at higher temperature. That enables the engine to achieve higher power at lower cylinder pressure. A new Venturi Jet Drain Oil Separator is the first of its type in the segment and is designed to ensure oil control in sustained full-load operation. The sealed system collects the fine mist of oil entrained in the blow-by gas and uses a small portion of the boosted air generated by the turbocharger to pump the collected oil back to the engine oil sump for re-use by the engine. A new electronic throttle valve regulates intake manifold pressure in order to increase exhaust gas recirculation (EGR) rates. It also contributes to smoother engine shutdown. Additionally, a cooled exhaust gas recirculation (EGR) system enhances performance and helps reduce emissions by diverting some of the engine-out exhaust gas and mixing it back into the fresh intake air stream, which is fed through the cylinder head for re-combustion. This lowers combustion temperatures, improving emissions performance by reducing NOx formation. An integrated bypass allows non-cooled exhaust gas to be fed back into the system to help the engine more quickly achieve optimal operating temperature when cold. Cold Start Improvements The new Duramax uses microprocessor-controlled glow plugs capable of 3 second starts in temperatures as low as -20 degrees F without a block heater. Ceramic glow plugs and automatic temperature compensation provide the capability. The automatic temperature compensation assesses and adjusts the current to each glow plug for every use, providing optimal cold start performance and durability. 2017 Chevrolet Silverado HD Regarding the competitive set efficiency, the previous gen Duramax fell behind the previous gen Power Stroke and fell significantly behind the 6.7L Cummins in the current RAM. I did not see anything stating they have improved efficiency so it may be just a numbers game. The new Duramax 6.6L turbo diesel is produced in Moraine, Ohio.
