International Truck and Engine has unveiled the specs for its MaxxForce 11- and 13-liter big bore engines, developed in concert with German truck-maker MAN and based on the
European company’s block. Both inline sixes will feature a high-pressure common-rail fuel injection system, series turbochargers with interstage coolers, and an innovative heat management system called Eco-Therm. With cylinder-block ribbing and other design enhancements, the engines are said to be “startlingly quiet”.

The MaxxForce 11 is a 10.5-liter with preliminary ratings of 330, 370, and 390 hp at 1900 rpm, with 1250, 1350, and 1450 lb ft of torque respectively, developed between 1000 and 1200 rpm. The 12.4-liter MaxxForce 13 has three preliminary ratings of 410, 430 and 475 hp at 1900 rpm, with 1450, 1550, and 1700 lb ft of torque between 1000 and 1200 rpm. Dry weight of both engines is 2244 lb.

The advanced fuel- and air-management systems provide “instant” throttle response to reach peak torque at 1000 rpm quickly, the company says.

High-pressure common-rail fuel systems control fuel injection with greater precision, introducing fuel into the cylinders at 26,000 psi in this case, providing more complete combustion and improved fuel efficiency.

The smaller primary turbo responds quickly to deliver air for take-off at low engine speeds, while the larger secondary turbo maintains peak power at high speeds and on grades. An interstage cooler after the first turbo and an aftercooler following the second turbo reduce the temperature of the intake air, increasing its density so that more air can be packed into the engine to achieve efficient, peak performance.

The Eco-Therm heat-management system is made possible by engine/truck integration. It controls coolant flow and temperature across the various coolers electronically to achieve optimal intake-air and exhaust-gas temperatures under all conditions. By maintaining exhaust-gas temperatures at optimal levels, there is an enhanced level of passive regeneration of the diesel particulate filter that leads to improved fuel economy.

Among other MaxxForce features is its compacted-graphite iron block It’s up to 300 lb lighter, says International, compared to other engine blocks using traditional gray iron. CG Iron is said to be 70% stronger and 40% stiffer with twice the fatigue strength of traditional gray iron.

The MaxxForce big-bore engines will be offered in ProStar linehaul tractors, TranStar regional-haul tractors, and WorkStar severe-service vehicles beginning late this year. They will be manufactured at a new International plant in Huntsville, Ala.