Navistar has updated its International A26 engine, enabling greater fuel economy while boosting power, and bringing the company's flagship 12.4-liter engine into compliance with Greenhouse Gas 2021 emissions regulations.
Previous design and system updates to the engine accounted for a 6% fuel efficiency improvement since the engine’s initial 2017 launch. The latest engine enhancements to the A26 provide an additional 4% fuel economy benefit – a 10% improvement since the engine's debut, and quite a leap for the powerplant that was, at its launch, already 5% more fuel efficient than the N13 engine model that the A26 replaced on the spec sheet.
Previous updates contributing to the 6% fuel efficiency improvement included optimized engine and transmission calibrations mated with the Eaton Endurant automated manual transmission – which International made standard last year on its on-highway trucks – a direct drive 2.15 ratio, and aerodynamic improvements to wheel coverings on drive axle wheels and the chassis.
The latest engine enhancements to the A26 focus more on engine design and system updates.
An increased compression ratio from 18.5:1 to 20.5:1 delivers higher combustion efficiency and fuel injection pressure from the 2500 bar high pressure common rail fuel system has been maximized. A more efficient design of the cylinder head coolant passages helps reduce parasitic loss at the water pump and the addition of a variable water pump provides more optimized run time, enabling better engine temperature control.
An optimized exhaust gas recirculation (EGR) cooler and intake throttle valve create more efficient charge air flow while the variable geometry turbocharger delivers boost air pressure across a wider range of engine speeds, loads and elevation. A higher horsepower output provides maximum power when needed, while operating at lower revolutions per minute (rpm) optimizes the amount of fuel consumed during operation.
Built from the MAN D26 engine crankcase, this latest version of the International A26 produces up to 515 horsepower and 1,850 lb.-ft. of torque. The original-generation maxed-out output at 475 hp and 1750 lb.-ft. of torque.
“The updated International A26 provides the horsepower you’d expect from a 15L engine, while working harder at lower engine speeds,” said Chet Ciesielski, vice president, 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.”