As first reported here several weeks ago, the MaxxForce 15 engine from International Truck & Engine will indeed be a modified version of today’s Caterpillar C-15. It will be built under licence, likely at the Navistar engine plant in Huntsville, Alabama starting some time in 2011, according to Navistar senior sales operations vice president Jim Hebe. He introduced the engine at the recent Mid-America Trucking Show.

It will not use Cat’s ACERT emissions technology, rather a variation on the air and fuel-management systems developed for – and still being tested on – the 2010 MaxxForce 13 engine. Like that one and others in the International lineup, it will also use “advanced” EGR, or exhaust gas recirculation, not the SCR aftertreatment system that all other engine makers will employ. International claims it can deal with nitrogen oxide, the target of EPA 2010 emissions standards, in-cylinder.

A crucial component is the engine’s high-pressure common-rail fuel system, as used on the MaxxForce 11 and 13, but with more robust injection pressure capability. Also used by Cummins and some others, such an injection system improves combustion efficiency while reducing noise and emissions.

The high-pressure common-rail design is electronically programmable to introduce fuel into the cylinders at very high pressure at low engine speeds and in several metered or staged sequences within each combustion cycle. Conventional heavy-duty diesel fuel systems don’t achieve peak pressure at these low engine speeds where fuel economy is inherently better, says International.

The system can deliver peak fuel pressure of up to 31,800 psi at any engine speed. This results in very efficient combustion with peak torque achieved at 1000 rpm (just above idle). This allows for earlier upshifts when accelerating and fewer downshifts when climbing hills. Operating the engine at low speeds also minimizes engine friction for better fuel efficiency.

Other features will include twin series turbochargers, said to allow immediate throttle response and strong top-end power to maintain highway speeds. The small first turbo winds up very quickly for good response at low engine speeds, the company says. As the air exits the first turbo it enters the interstage cooler where it’s cooled, increasing air density as it flows into the larger, second turbo. This influx of cool, dense air provides greater flow through the larger turbocharger in order to provide peak power.

International says the technology has been tested and proven in real-world conditions on the MaxxForce 13, but many millions of miles of additional testing and validation will take place on the 15-liter platform before it’s ready for the marketplace.

We’ll see ratings from 435 to 550 hp with torque output from 1550 to 1850 lb ft, including two multi-torque models..