International details new medium-duty engines

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International’s new medium-duty engine line will feature in the MaxxForce DT, 9 and 10 models a variety of evolutionary features that further the use of big-bore-type features to enhance durability and reliability, the company recently announced. Also announced was the launch of to “provide a global perspective on the engine offerings,” said Engine Group President Jack Allen.

The three new MaxxForce I-6 models include the 7.6-liter MaxxForce DT (in combinations of 210-300 hp, 520-860 lb.-ft. of torque), the 9.3-liter MaxxForce 9 (300-330 hp, 800-950 lb.-ft. of torque) and the 9.3-liter MaxxForce 10 (310-350 hp, 1,050-1,150 lb.-ft. of torque).

The DT powers DuraStar and WorkStar models as well as some school and commercial buses. The MaxxForce 9 model will equip certain DuraStar, WorkStar and CXT models. The MaxxForce 10 will be available for WorkStar and TranStar models. All are set for manufacture at International’s Melrose Park, Ill., plant and release in late 2007.

The 2007-spec’d ’08 engines will be an emissions-reducing evolution of the DT engine, introduced in the 1970s and long used by medium-duty operators. All three feature essentially the same displacements and architecture of the 2006 DT variants, but with improved reliability, said Phil Gronberg, chief engineer of the MaxxForce line.

A molded foam wiring harness is shaped to fit around the engine with less rubbing and chafing, increasing ease of installation and service. Replacing the old dual-box control modules for aftertreatment systems of years past is a single-box controller. And a closed-crankcase ventilation system doesn’t require in its life any routine service — there will be no significant performance degradation over time, Gronberg said. No filters to change, either.

The diesel particulate filter is regenerated by an in-cylinder dosing process that doesn’t utilize an injector in the exhaust system itself but a late dose of fuel that exits on the exhaust stroke to periodically raise the temperature of the exhaust enough to oxidize matter trapped in the DPF.

Gronberg says this won’t have an effect on the company’s recommended oil change intervals, and tests have shown that, even with regeneration intervals as short as 200 to 400 miles, fuel mileage will not be affected adversely. In fact, the company has seen in medium-duty pickup and delivery applications an increase in fuel economy due to “other changes within the integrated package to offset the losses,” said Persio Lisboa, director of engine marketing.

Other notable features include a big-bore-modeled wet cylinder-sleeve design to ensure uniform cylinder cooling and reduce or eliminate hot spots. And as always, this design is fully rebuildable in-chassis, unlike parent-bore designs. Six headbolts rather than four enhance head gasket sealing and ensure overall stability.