Chevy announced this week that its first-ever inline-six turbo diesel, the 3.0-liter Duramax, has brought class-leading torque and horsepower to the 2020 Silverado ½-ton pickup.
The all-new Duramax incorporates advanced combustion and emissions technologies to optimize performance and efficiency. It is priced identically to the 6.2-liter V8 as a $2,495 premium over a 5.3L V8 model or $3,890 over a 2.7-liter Turbo model.
“From the moment the engine is started, to its idle, acceleration and highway cruising, the 3.0-liter Duramax performance will change perceptions of what a diesel engine can offer in refinement,” said Nicola Menarini, director for Diesel Truck Engine Program Execution. “With advanced technologies that draw on global diesel expertise, it’s a no-compromise choice for those who want the capability and driving range of a diesel in a light-duty truck.”
Available on LT, RST, LTZ and High Country models, the 3.0-liter Duramax diesel rounds out the new Silverado’s range of six propulsion choices, each designed to suit customers’ needs for performance, efficiency, technology and value. It’s rated at an SAE-certified 277 horsepower and 460 lb.-ft. of torque delivering 95 percent of peak torque at just 1,250 rpm. Peak torque is sustained from 1,500 rpm through 3,000 rpm.
The 3.0-liter Duramax is paired with GM’s 10L80 10-speed automatic transmission, featuring a centrifugal pendulum absorber torque converter that reduces vibrations to improve smoothness, reinforcing its performance, efficiency and refinement. This combination also offers exhaust braking, which uses the diesel engine’s compression to help slow the vehicle, requiring fewer brake applications by the driver when in Tow Haul mode.
New engine technology
The inline six-cylinder engine features a lightweight aluminum block and cylinder head. Active Thermal Management enhances efficiency and cold-weather warm-up. Ceramic glow plugs also help with shorter heat-up times and a quicker cold start, meaning the engine block heater is not needed until -22 degrees F.
The water charge air cooler, coupled with low pressure EGR, reduces time to torque. The variable geometry turbocharger helps provide a greater balance of performance and efficiency, and an electronically variable intake manifold helps optimize performance across the rpm band.
Compared to a DOHC V6, the inline-six architecture offers greater efficiency from the reduced friction of operating only two camshafts and their associated valvetrain components. The I6 configuration balances primary and secondary forces without the need for balancing shafts.
“In addition to reduced friction, the architecture enables smooth operation,” Menarini said. “The new Duramax 3.0-liter elevates the 2019 Silverado with one of the most refined and efficient diesel engines in the segment.”
With supporting elements such as a tuned air induction system and other noise-attenuating elements, the 3.0-liter Duramax is designed for exceptionally quiet and smooth operation at all engine speeds.
The 3.0-liter Duramax cylinder block is made of a cast aluminum alloy that provides the strength required to support the high combustion pressures that occur within a diesel engine, while also offering an approximately 25 percent mass savings over a comparable cast iron engine block. Iron cylinder liners are used within the aluminum block to insure truck durability.
There are seven nodular iron main bearing caps that help ensure the block’s strength under those high combustion pressures, while also enabling accurate location of the rotating assembly. A deep-skirt block design, where the block casting extends below the crankshaft centerline, also contributes to the engine’s stiffness and refinement. It’s complemented by a stiffness-enhancing aluminum lower crankcase extension attached to the main bearing caps.
The rotating assembly consists of a forged steel crankshaft, forged steel connecting rods and hypereutectic aluminum pistons. The alloys in the respective castings for the rods and pistons make them lightweight and durable. Silicon is blended with the aluminum for heat resistance and tolerance within the piston cylinders, which enhances performance and reduces engine noise.
A thick piston crown — the top of the piston — and reinforced top ring add strength to support increased cylinder pressures enabled by turbocharging and the engine’s high 15.0:1 compression ratio.
DOHC Cylinder Head and Rear Cam Drive
Overhead camshafts offer a direct, efficient means of operating the valves, while four valves per cylinder activated by maintenance-free finger followers with hydraulic lash adjusters increase airflow in and out of the engine. This arrangement is integrated on the Duramax 3.0L’s lightweight aluminum cylinder head, which is topped with a lightweight composite cam cover that incorporates the crankcase ventilation and oil separation systems.
A pair of lightweight, assembled camshafts actuates 28.35 mm diameter (1.12-inch) intake and 24.55 mm diameter (0.97-inch) exhaust valves. The camshaft drivetrain is uniquely located at the rear (flywheel side) of the engine, for greater refinement and packaging considerations for the comparatively long inline-six. A crankshaft-driven chain drives the high-pressure direct-injection fuel pump, while a chain driven by the fuel pump drives both intake and exhaust camshafts. A smaller belt drives the variable flow oil pump from the crankshaft.
Additional Technology Highlights
Variable geometry turbocharging enables the Duramax 3.0-liter engine to deliver class-leading horsepower with minimal effect on overall efficiency. The system uses closed loop controlled vanes position and sophisticated electronic controls to automatically adjust boost pressure to the desired value based on engine running conditions and instantaneous power demand. The liquid-cooled turbocharger features a low-friction ball-bearing shaft and is mounted close to the exhaust outlet of the engine for quicker spool-up of the turbine and quicker light-off of the exhaust catalyst. A water-to-air intercooling system produces a cooler higher density air charge for greater power. Maximum boost pressure is 43.5 psi (300 Kpa) absolute.
Low-pressure EGR: The Duramax 3.0-liter utilizes new low-pressure Exhaust Gas Recirculation to optimize performance and efficiency. The EGR system diverts some of the engine-out exhaust gas and mixes it back into the fresh intake air stream, which is drawn into the cylinder head for combustion. That lowers combustion temperatures and rates.
Traditionally, EGR systems in diesel applications recirculate exhaust gases between the two high-pressure points, the exhaust manifold(s) and intake manifold. However, it generally requires efficiency-robbing assistance from the turbocharger or other supporting elements to achieve the pressure differential required for sufficient EGR flow rates.
The new low-pressure system adds to the high-pressure system, supporting continual adjustment of exhaust backpressure for more efficient operation. It recirculates gases between the low-pressure points in the exhaust system (downstream of the particulate filter) and after the compressor inlet.
When the low-pressure EGR is activated by an electronically controlled valve, the engine burns exhaust gas that has already passed through the particulate filter. That increases the turbocharger’s efficiency, which helps overall vehicle efficiency without deteriorating the rate of particulate matter emitted by the engine.
A variable intake manifold offers dual air intake pathways for each cylinder. Electronically controlled flaps — one for each cylinder — shorten or lengthen the airflow to each cylinder. This optimizes the airflow into the engine and improves performance and responsiveness across the rpm band, particularly at lower engine speeds.
A variable-pressure oiling system with a continuously variable-displacement vane oil pump enhances efficiency by optimizing oil pressure as a function of engine speed and load. With it, the oil supply is matched to the engine requirements rather than the excessive supply of a conventional, fixed-displacement oil pump. The engine uses low-friction Diesel Dexos 0W20 oil.
Oil jets located in the block are employed for performance and temperature control. They target the inner core of the piston with an extra layer of cooling, friction-reducing oil. The jets reduce piston temperature, allowing the engine to produce more power and enhance long-term durability than engines without the technology.
Active Thermal Management helps the engine warm up quickly to achieve and maintain its optimal engine temperature for performance and efficiency over the entire engine operating range. The system uses a three-actuator rotary valve system to distribute coolant through the engine in a targeted manner. It sends heat where it’s needed to warm up the engine to reduce friction and heat the passenger cabin or cools when needed for high-power operation. The Duramax 3.0L also features split cooling between the block and head.
Common rail direct fuel injection of 2,500 bar (36,250 psi) helps generates class-leading horsepower and torque. The system’s pressure is generated by an engine-driven twin-piston pump sending fuel to solenoid-activated injectors with nine-hole nozzles that support precise metering of the fuel for a smooth idle and lower combustion noise. The fuel system is capable of multiple injections per combustion cycle — up to 10 times per injector — for more consistent and stable combustion performance that translates into smoothness and refinement, particularly at idle.
Electronic throttle valve: The Duramax 3.0L features an electronic throttle valve to regulate intake manifold pressure in order to optimize exhaust gas recirculation rates. It also contributes to a smooth engine shutdown via a more controlled method of airflow reduction.
Ceramic glow plugs used in the Duramax 3.0L heat up more quickly and hotter than conventional metal-based glow plugs, helping the engine start and heat up more quickly in cold weather. The Duramax 3.0L achieves unassisted and assisted starting temperatures of -22 F (-30 C) and -40 F (-40 C) respectively.
Stop/start technology helps optimize efficiency in city driving. The driver-selectable system shuts off the engine at stoplights and other stop-and-go situations. The engine automatically restarts when the driver takes their foot off the brake.