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International A26; The Lightest I-6 in the Class 8 Truck Market

“The Alpha Project” Delivers the Lightest Big-Bore Diesel Engine in the Class 8 Truck Market

John Lehenbauer
May 16, 2017
Photographers: Courtesy of Manufacturer
International’s “Project Alpha” initiative was created to give powertrain engineers a clean slate to work from in an effort to advance the company’s diesel-engine production. Starting from square one gives engineers the ability to be creative and to eliminate many of the complexities normally associated with modern power units. Simplicity and the use of already proven components are key to the project. Development of simpler engines means fewer things wrong and there’s less to maintain, which translates to fewer repairs and more uptime for the trucks and machines the engines power. Weight reduction is another benefit of reducing the number of components, and by using parts that are already established in the marketplace and not new untested pieces, reliability is increased. The all-new A26 is the first engine produced under the Project Alpha initiative.
The A26 is a 12.4L diesel engine that is purpose-built for Class 8 over-the-road trucks. The new powerplant produces 475 hp and 1,750 lb-ft of torque and is lighter, quieter, more fuel efficient, and engineered for durability and minimal downtime. At 2,299 pounds, the engine is 50 pounds lighter then the N13 it replaces and 600 to 700 pounds lighter than the 15.0L big-bore oil-burner that’s traditionally used in Class 8 trucks. To further reduce weight, the simplistic philosophy used on the A26 was applied to its associated accessories, shaving an additional 200 pounds.
Photo 2/7   |   The International A26 diesel engine is the final result of a program called Project Alpha. The project’s main goal was to design an engine from a clean slate and make it simpler with proven technology.
Every part of the A26 is engineered with a purpose. The MAN D26–sourced compacted-graphite-iron crankcase is stronger, more fatigue-resistant, and lighter than a gray-iron block. A composite valve cover and shot-peened aluminum flywheel housing also help reduce weight.
Durability is important. That is why larger piston pins, connecting rods, and bushings are employed in International’s newest engine, optimizing the load distribution of the rotating assembly. The piston skirts are treated with a low-friction coating and feature advanced ring geometry to minimize parasitic loss and enhance fuel economy. A hollow camshaft reduces weight and features tool-grade steel lobes for increased longevity, and smaller cooling jets are used to increase oil pressure. By increasing the oil pressure, piston lubrication is improved and oil-change intervals are extended.
Photo 3/7   |   This cutaway provides a look at the inner workings of the A26. It also offers a glimpse of the EGR and new variable-geometry turbocharger.
A simpler variable-geometry turbocharger with a single-stage titanium compressor wheel is employed for improved reliability. The VGT can deliver boost across a wide range of speeds, loads, and altitudes, and it also increases engine-braking power by as much as 67 percent. The ’charger is paired with a high-pressure, common-rail fuel system that further enhances fuel economy and reduces emissions. The HPCR is optimized with multiple injection events and a 2,500-bar (36,300-psi) Bosch pump.
The four-valve-per-cylinder, gray-iron cylinder head used on the A26 is a new design for International. Its coolant passages are 50 percent less restrictive. By reducing restriction, there is less parasitic power loss at the water pump, which helps increase the engine’s overall efficiency. The computer-modeled head is designed with free-breathing intake ports and higher-flow exhaust ports to optimize the flow of air in and out of the cylinders.
Photo 4/7   |   International A26 Rear Side Turbo
Reducing the amount of engine noise in the cab of an over-the-road truck is also important. To combat excessive noise, the A26’s crankcase features a unique, sculpted design that allows it to absorb vibration and reduce noise harshness. The engine also uses a specially designed rubber gasket to isolate the oil pan from the block, which keeps the pan from amplifying noise. A six-blade cooling fan, specially designed timing gears, and sophisticated ECM calibration further reduce the racket.
By starting from scratch, developers were able to scrutinize every part on or inside the International A26 diesel engine to ensure it gives Class 8 trucks the best efficiency, power, and durability possible.

SPECIFICATIONS

Engine: International A26
Displacement: 12.4L (275 ci)
Engine Layout: I-6
Valvetrain: SOHC 24-valve
Bore x Stroke: 4.96 x 6.54 inches (126 x 166 mm)
Compression Ratio: 18.5:1
Head material: High-performance gray iron
Block material: Compacted-graphite iron
Piston material: Forged steel
Power: 475 hp
Torque: 1,750 lb-ft
Emissions: 2017 U.S. EPA
Induction: Variable-geometry turbocharger
Exhaust: Ductile iron (HiSil Moly)
Intercooler: Air-to-air
Cooling System: Liquid-cooled
Fuel System: High-pressure, common-rail
Lubrication System: Wet sump
Lubrication Capacity: 42 quarts
Dry Weight: 2,299 pounds
Length: 59 inches
Width: 38 inches
Height: 43 inches

Sources

International
internationaltrucks.com

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