Navistar Updates A26 Engine, Improves FE by 4%

December 1, 2021

Ryan Gehm

Since the initial launch of the International A26 engine five years ago for the Class 8 market, Navistar engineers have tweaked the power plant to improve fuel economy (FE) by 10%. Previous design and system updates account for a 6% FE improvement, while the latest significant enhancements to the 2021 Greenhouse Gas (GHG) A26 engine provide an additional 4% benefit.

“These latest updates to the International A26 highlight Navistar’s ongoing commitment to improved vehicle efficiency and total cost of ownership for our customers,” said Diane Hames, VP of Marketing. “Every incremental change helps to forge a path toward that more efficient future.”

The previous updates contributing to the 6% fuel-efficiency improvement include more optimized engine and transmission calibrations mated with the Eaton Endurant automated manual transmission, a direct drive 2.15 ratio and aerodynamic improvements to wheel coverings on drive axle wheels and the chassis.

The latest engine design and system updates include combustion enhancements and optimized engine temperature control. An increased compression ratio, from 18.5:1 to 20.5:1, delivers higher combustion efficiency along with maximized fuel injection pressure from the 2,500-bar (36,260-psi), high-pressure common-rail fuel system. Efficient design of the cylinder-head coolant passages helps to reduce parasitic loss at the water pump. The addition of a variable water pump provides more optimized run time versus constant “on.”

Air management system updates feature an optimized exhaust gas recirculation (EGR) cooler and intake throttle valve that create more efficient charge air flow. The variable geometry turbocharger delivers the desired boost air pressure across a wide range of engine speeds, loads and elevation.

At 2,314 lb (1,050 kg), the latest-generation A26 is the lightest engine in its class, Navistar claims. The 13-L engine reportedly weighs 600-700 lb (272-318 kg) less than typical 15-L big-bore engines. Higher power output while operating at lower rpm optimizes the amount of fuel consumed during operation. Built from the proven MAN D26 engine crankcase, the latest version of the A26 produces up to 515 hp (384 kW) and 1,850 lb.-ft. (2,508 Nm), compared to 475 hp (354 kW) and 1,750 lb.-ft. (2,373 Nm) for the previous version.

“The updated International A26 provides the horsepower you’d expect from a 15-L engine, while working harder at lower engine speeds,” said Chet Ciesielski, VP of On-Highway Truck Business. “The active torque management at the pedal delivers the required amount of torque at the moment it’s needed while providing a smoother shifting experience for the driver.”

The new-generation A26, which was on display during the recent American Trucking Associations’ Management Conference and Exhibition in Nashville, Tenn., is available for order in the International LT Series of long-haul vehicles, RH Series of regional haul vehicles, the HX Series for heavy-haul and various construction applications and the HV Series for select vocational applications.