This article also appears in
Subscribe now »

A six-blade fan was decided over the previous eleven-blade, which allows for quieter operation in addition to reducing power consumption.

International develops new, lighter A26 engine to replace N13

Any time a new engine is announced, it is major news. Pairing a new engine with a new approach to engine development is even bigger news. International Truck recently unveiled its all-new engine for the Class 8 market called the International A26. Along with that came news of an initiative called Project Alpha, which brought together a small team of powertrain engineers dedicated to a new perspective on engine development.

"The A26 was designed from the ground up to deliver industry-leading uptime, durability and reliability," said Darren Gosbee, vice president of advanced engineering. The 12.4-L A26 sources a MAN D26 inline 6-cylinder crankcase from their partnership with the Volkswagen Group and surrounds it with numerous all-new components to optimize four key criteria: uptime, fuel efficiency, weight and NVH (noise, vibration and harshness).

The engine weighs only 2299 lb (1043 kg), which is 55 lb (25 kg) less than the Navistar N13 engine it replaces and 600-700 lb (272-318 kg) lighter than traditional 15-L big bore engines. Despite the reduction in weight, the engine can still produce up to 475 hp (354 kW) and 1750 lb·ft (2373 N·m).

Simplicity was one of the focal points of the engine design to deliver maximum uptime. “The A26 is as simple as a modern engine can be, and we’ve built uptime into every part of the development process, from design to calibration to testing,” said Gosbee. Larger piston pins, connecting rods and bushings are used for better load distribution. Smaller piston cooling jets have increased oil pressure and help extend oil change service intervals up to 70,000 mi (112,654 km).

Other improvements across engine systems have helped deliver up to a 5% increase in fuel economy. The new BorgWarner single-stage variable geometry turbocharger leads off a simplified air management system. The Bosch 2500-bar (36,259-psi) high pressure common rail fuel system and new cylinder head with coolant passages that are 50% less restrictive help reduce both fuel consumption and emissions.

Simplification also helped lead to keeping the International A26 light weight, in addition to component material choices. A titanium compressor wheel was used instead of aluminum for improved fatigue life while continuing to reduce weight. Composite valve covers and an aluminum flywheel housing provided additional weight savings.

To improve NVH, the A26 has been given a new sculpted crankcase with an isolated oil pan and rubber gasket designed to absorb vibrations. A six-blade fan was decided over the previous eleven-blade, which allows for quieter operation in addition to reducing power consumption. The engine calibration is also programmed for reduced engine noise.

Jacobs Vehicle Systems collaborated with Navistar engineers to provide a factory-installed compression release engine brake for the A26 engine. “By leveraging the benefits of the new variable geometry turbo, the A26 engine brake performance increased up to 67% at lower engine speeds and higher altitudes,” according to Jacobs. Other stated benefits include a reduction in the need for downshifting and improved NVH.

Project Alpha initiative speeds development

All of these improvements were the goal of Project Alpha, a brand-new initiative by International for this engine’s development. “Project Alpha has fundamentally changed how we design diesel engines,” says Bill Kozek, president of Truck and Parts. The group was formed using fewer members to speed up and focus engine design decisions. They were also given more autonomy in their decision making to not only meet the 2017 emissions regulations but improve the overall product performance in those four key areas.

One of the mandates Project Alpha decided on was to leverage proven industry technologies over testing new ones on customers. “Keep the best and improve the rest,” was a mantra for Jim Nachtman, marketing manager of Heavy-Duty Product Line. The crankshaft, main and rod bearings, EGR cooler and valves, oil and fuel filters, air compressors and flywheel housing along with several other components were carried over from the Navistar N13 engine. However, many of the reciprocating components like the connecting rods, piston pins and pistons were replaced to increase the compression ratio up to 18.5:1. A slower, single-speed water pump was decided over a variable speed pump to improve the fuel economy without the complexity.

The Project Alpha team put the A26 engine through hundreds of thousands of hours of dynamometer testing at severe engine speeds and loads. “It’s been tested to extremes and meets a demanding B10 design life standard for an unprecedented 1.2 million miles,” said Kozek. The engine was temperature tested as low as -40°F (-40°C), which was aided by a switch to Compact Graphite Iron (CGI) for the crankcase which has better thermal fatigue than previous traditional gray iron.

The A26 will now be available in the International LT Series trucks. International is backing the engine with a two-year, unlimited mile warranty. It is the first of a new wave of engines for International trucks. The Project Alpha team and A26 engine are a new beginning for the brand.

Continue reading »