Lighter, smaller Inter engine
NORTH AMERICAN TRUCKMAKER NAVISTAR HAS launched a new 12.4-litre engine – emphasising its small size and light weight.
e International A26 is based on Navistar’s previous N13 (and originally the MaxxForce 13) engines, which also displaced 12.4-litres – giving a clue to the source of many of the new engine’s hard parts. Most of the rotating parts are carryover and also feature in the German MAN D26, from which the A26 engine is derived.
e use of the 12.4-litre number is deliberate, to underscore that this is smaller and lighter – by 600 to 700 pounds (272-317-kilograms) – than a 15-litre. It weighs-in at 2299 lbs (1042kg) thanks to lightweighting features including an aluminium clutch housing and built-up modular camshaft, both of which featured on the N13 engine and on the D26.
Development of the A26 took a fresh approach, says Navistar – one “that emphasised simplicity over complexity and using only proven components to deliver industry-leading uptime.”
e success of the project, says Bill Kozek, Navistar president of truck and parts, has “fundamentally changed how we design diesel engines.”
Every component is engineered to maximise uptime. From the cylinder head gasket up, the A26 is an all-new design, far simpler than the N13, Navistar says. Designed to be as simple as possible to guarantee reliability, durability and maximum uptime, the head ows more air than previously with reduced friction and pumping loses.
Featured is a Bosch common-rail fuel injection running at 2500 bar (36,300 psi) which gives the A26 a range of 370 to 475-horsepower (275-354kW ), and torque ratings between 1350 and 1750 pounds-feet (1830-2372Nm). A single variable geometry turbocharger replaces the series turbos and features a titanium wheel for durability.
ere’s also a simple plug-in control module for easy service without removing the turbo. With a far simpler cooling system, without the inter-stage charge-air cooler, the A26 is 55 lb (25kg) lighter than the engine it will eventually replace.
“e A26 was designed from the ground up to deliver industry-leading uptime, durability and reliability,” says Navistar’s
e 12.4-litre A26 has its roots in earlier Navistar and MAN engines – Navistar opting for proven components in the interests of optimising uptime. e cylinder head (below) is entirely new – and, like the rest of the engine, was designed with simplicity to the fore VP of advanced engineering, Darren Gosbee.
“e 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.”
Navistar says SAE testing shows the A26 has 5% better economy than the N13 from three years ago. When installed in the ProStar replacement, the International LT, there’s a 9% improvement in fuel economy.
Combustion control makes the A26 the quietest engine in the International lineup, says the company. e A26’s sculpted crankcase, which is isolated from the oil pan through a specially-designed rubber gasket, absorbs vibration and reduces harshness. With a far lower thermal load on the cooling system, the A26 goes from an 11-bladed fan to a quieter six-blade fan. Along with specially designed cam/accessory gear teeth and sophisticated calibration, the engine is designed for reduced noise.
e cylinder block is cast and machined in Navistar’s facility in Brazil and the A26 engine is to be built up at the Alabama International engine plant.
e A26 went into production last month and will be available in the US in International’s new linehaul LT (ProStar replacement) and the regional haul RH from this month. e N13 remains in production till the end of the year for Inter’s vocational HX and all Class 8 models still with Star still in their names (ie WorkStar, PayStar etc).