GM Revs Up Heavy-Duty Diesels

General Motors Co. says the diesel-powered, heavy-duty versions of its 2017 Chevrolet Silverado and GMC Sierra trucks will be the most powerful pickups the carmaker has ever offered.

Mated with a 6-speed Allison automatic transmission, the redesigned 6.6-liter Duramax V-8 diesel that powers the vehicles generates 445 hp and a whopping 910 lb-ft of torque. This compares with 397 hp and 765 lb-ft for the diesel V-8 in the outgoing 2016 trucks.

The increased output puts the Silverado/Sierra pickups on par with Ford Motor Co.’s 2017 super-duty diesel-powered pickups offered with engines that make as much as 440 hp and 925 lb-ft of torque. Fiat Chrysler Automobiles NV’s aging Ram lineup tops out with a Cummins diesel rated at 385 hp and 850 lb-ft.

GM is publicly unveiling the trucks today at the Texas State Fair in Dallas. Sales are due to start early next year.

GM says the Duramax diesel is 90% new. But by maintaining the previous V-8’s short stroke (99 mm) and 103 mm bore spacing, GM says it will be able to build the new powerplant on the same production line at its Moraine, Ohio, plant.

The 2017 diesel gets a stronger cast-iron engine block, redesigned aluminum cylinder heads, a new crankshaft with improved bearing surfaces and a venturi jet drain oil separator that filters oil mist out of the blow-by gases. Other changes include an electronically controlled turbocharger, revised exhaust gas recirculation with a single cooler and integrated bypass, and a new fuel system with proprietary GM controls.

A new closed-loop glowplug temperature control unit, which GM describes as a segment first, uses sensors to better manage operations and enhance cold weather starting. Changes to the way the aluminum pistons are produced improve their heat tolerance, according to the carmaker.

The new trucks also feature a patent-pending air intake system. GM says the design drives cool, dry air into the engine to enhance power and overall engine performance.