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Until now, if you wanted big-bore power in your International trucks you had to go to Cat or Cummins – an arrangement International made clear it wanted to change. Today, after three years of development, International has its engine: In Las Vegas in January, company officials pulled the curtain off of the new MaxxForce 11 and MaxxForce 13 big-bore diesel engines.
Designed in conjunction with International’s European partner MAN, the new engines are specifically engineered for vertical-integration in the North American Class 8 marketplace. They will be offered as optional equipment exclusively in International ProStar line-haul tractors, TranStar regional-haul tractors and WorkStar severe service trucks.
The shared International/MAN technology has yielded six engine models ranging from 330 to 474 horsepower and 1,250 to 1,700 pound-feet of torque. All are designed to be fuel-efficient, powerful, durable and quiet. These attributes are largely thanks to the engines’ compacted-graphite iron blocks – a first for the North American market, according to International – and a host of other innovations including optimized fuel system electronics and air management systems and EGR and exhaust aftertreatment technologies developed by International specifically for high performance at low emissions levels. “These advanced features yield four primary benefits,” says Jack Allen, president, International Engine Group, “including outstanding fuel economy; excellent power and torque; quiet operation with low noise, vibration and harshness; and high strength with added weight.”
A company on the move
It’s been interesting to watch International’s technology evolution over the past few years. Seven years ago, International was a leading commercial truck manufacturer with a reputation for solid vehicles. But their medium-duty conventional line was more than 20 years old – and some of that truck’s drivetrain and vehicle components had been in production for almost 40 years. International had market share, but saw competitors launching innovative trucks and finding new ways to use technology. The company knew it had to up the ante.
And so it introduced its Next-Generation 4000 Series vocational truck – a dramatic step forward for International in terms of styling, ergonomics and telematics. That same year – in 2001 – International officials promised that the 4000 model was the beginning of a technologically-innovative International and the coming years would see a flurry of new vehicles, engines and business solution offerings.
Since then, International has become one of the most dynamic OEMs in the on-highway truck industry, as witnessed by a slew of new trucks for both civilian and military applications. In recent news, International acquired General Motors’ Kodiak and Topkick vocational truck lines, and is still supplying PowerStroke diesel engines to GM’s arch-rival Ford. And, finally, the company made major waves at the Chicago Auto Show in February with the launch of its ultra-funky, retro-styled LoneStar conventional tractor.
New block casting technology yields stronger, lighter and quieter engine platform
Clearly something’s up at International. So it was no surprise to learn that this 154-year old, technologically-savvy truck manufacturer worked closely with its MAN European partner to nail down the latest engine technology for its MaxxForce diesel engines. And this meant starting with the basics.
All MaxxForce engines feature blocks cast from compacted-graphite iron, which has a higher inherent strength than cast-iron for an extremely strong block foundation. But, because compacted-graphite iron castings do not have to be as thick or heavy as cast-iron in order to achieve the durability required for heavy-duty diesel engines, the overall block weight is, in International’s words, up to several hundred pounds lighter than an engine block cast from gray iron of equivalent strength.
“Compared to gray iron, compacted graphite iron is 70 percent stronger and 40 percent stiffer with double the fatigue limit,” says Steve Perkins, senior sales specialist, International Engine. “These qualities are thanks to composite-graphite iron’s makeup. A precise amount of magnesium is added to the base iron compound in a highly controlled process to create this new, stronger compound.”
Perkins says International’s use of CG iron in MaxxForce engines has paid several dividends. Because the iron is lighter, designers were able to use large, pronounced ribbing in the crankcase, which, when combined with the engines’ thick rubber oil pan gasket and laminate oil pan construction, helps to significantly reduce engine noise.
International claims its new big bore engines are the first in North American Class 8 segment to feature a high-pressure common-rail fuel system – technology the company notes has already been proven on millions of diesel engines in both Europe and North America.
High-pressure, common-rail systems are electronically programmable to introduce fuel into the combustion cylinders at extremely high pressure and in several metered or staged sequences with each combustion cycle, depending on engine speed. In contrast, conventional Class 8 diesel fuel systems do not achieve peak injection pressures at low engine speeds where fuel economy is inherently better.
Perkins says the MaxxForce common-rail system can deliver peak fuel pressure of up to 26,000 psi at any engine speed. “The system can deliver up to three separate injections per combustion stroke,” he explains. “This results in highly efficient combustion with peak torque achieved at 1,000 rpm, or just above idle speed.”
The net result, Perkins says, is earlier upshifts when accelerating and fewer downshifts when climbing hills. Operating the engine at low speeds also minimizes engine friction, which, in turn, leads to better overall fuel economy.
A final benefit Perkins points to is common-rail injection eliminates diesel engine “clatter” from the combustion event. “Conventional diesel engines dump one full shot of fuel into the combustion chamber at the same time,” he notes. “The result is a large amount of fuel rapidly burning and expanding in each cylinder. This rapid expansion causes that well-known knocking sound in the cylinders which is not only noticeable, but also contributes significantly to driver fatigue.”
In another North American first, Perkins says the MaxxForce 11 and MaxxForce 13 are the first Class 8 big bore engines to feature twin-series turbochargers operating in unison with International’s Eco-Therm heat-management system. “This system delivers superior cold weather operation with faster warm-up times,” Perkins explains. “The Eco-Therm system also improves exhaust temperature control for enhanced passive regeneration of the diesel particulate filer, resulting in improved fuel economy.”
The twin turbochargers are also important. The smaller, primary, turbo responds quickly to deliver cool, clean air to the engine to immediate take-off at low engine speeds. The larger, secondary, turbo maintains peak power at high engine speeds and during grade changes. An interstage cooler after the first turbo and an after-cooler following the second reduce the temperature of intake air, increasing its density as it begins the combustion process. “In simple terms, this means we can pack more air into the engine to achieve efficient, peak performance regardless of road conditions,” Perkins adds.