A new heavy-duty diesel engine platform from Daimler is putting a global spotlight on fuel economy and emissions-reduction technology. The platform’s four engines will be available in Freightliner, Sterling, Western Star, Mercedes-Benz, and Mitsubishi Fuso heavy-duty vehicles.
“Daimler Trucks invested a total of $1.5 billion in the development of this heavy-duty engine platform,” said Andreas Renschler, Member of the Board of Management for Daimler AG and Head of Daimler Trucks. That $1.5 billion—which includes $275 million for machinery and other alterations at Detroit Diesel’s Redford, MI, assembly plant—is “a significant investment, but one that will pay off,” added Renschler.
The 14.8-L, inline six-cylinder DD15 is the first in a series of heavy-duty engines. Three other inline six-cylinder displacements will also be produced: a 10.6-L, a 12.8-L, and a 15.6-L. “The engines have unique blocks and cylinder heads. But the 15.6-L—except for crankshaft, connecting rod, piston, and a portion of the air system—will have complete commonality with the 14.8-L. In the other cases, it’s less than 50% commonality,” said Mark Groeneweg, Senior Manager of Heavy Duty Engine Platform Development in North America for Detroit Diesel.
All North American engine displacements will use the same high-pressure fuel pump, oil module, and fuel module. Daimler Trucks will manufacture alternate versions of the engine series in Germany via Mercedes-Benz, in Japan via Mitsubishi Fuso, and in the U.S. via Detroit Diesel.
The DD15 was designed with emissions reduction in mind. “Using the experience and resources of the Daimler family, we started from the ground up and integrated environmental-compliance features into the design of the engine,” said Chris Patterson, President and CEO of Freightliner, which as of January 2008 was renamed Daimler Trucks North America. One major technical feature of the new engine is that much of the exhaust gas gets captured and reused.
“The whole idea is taking energy that normally goes out the exhaust pipe and redirecting it—using an axial turbine—to convert that so-called waste energy into power,” said Groeneweg. He explained that thermal recovery is a relatively straightforward process, with high-pressure exhaust gas exiting the turbocharger through the turbo-compound axial power turbine where it is converted into shaft power, then transferred to the rear geartrain and into the crankshaft.
“The turbo compound system works in tandem with the turbocharger to provide an increase of up to 50 bhp in engine output, and it facilitates EGR [exhaust gas recirculation] transport without the penalty of turbo-lag,” said Groeneweg. The DD15 uses the same diesel particulate filter that is used on the Detroit Diesel Series 60 engine and the MBE 4000.
Another DD15 technical highpoint is the use of an amplified common-rail fuel system that can produce up to five injection events per combustion cycle. “Instead of pumping the fuel rail up to 1800 bar, which is relatively common for heavy-duty common-rail systems, this system is considerably less than that—actually it’s less than 900 bar—and that means reduced stress in the external fuel rail, fuel lines, and fuel pump,” said Groeneweg. The 900-bar (13,050-psi) fuel pressure is hydraulically amplified within the injector to achieve the necessary injection pressure, which is currently a peak injection pressure of 2100 bar (30,460 psi). Full injection pressure is controlled by two solenoid valves.
Lessons learned from past engine programs also influenced design. “If you look at the DD15, you’ll see the DNA of the 14.0-L Series 60 and the 12.8-L MBE 4000. But you’ll also see completely new features, like the turbo compounding system and the amplified common-rail fuel system. The cylinder head, block, geartrain, lubrication system, cylinder kit, cooling system, and exhaust aftertreatment device are all harvested from the collective corporate experience,” said Groeneweg, noting that the compacted graphite iron used for DD15’s cylinder heads is produced at Daimler’s foundry in Mannheim, Germany.
Although the DD15 is based on a common engine platform, it is also designed for a specific geographic region. “A typical example is the oil pan, where the North American version has extended capacity and fits like a glove in a conventional Freightliner Chassis, but would not be optimal in a European Cab Over Mercedes Truck,” said Jim Gray, North American Program Director for the DD15 engine.
Added Groeneweg, “We want commonality globally for cost reasons, but we can’t compromise what’s needed for Europe, for Japan, and for North America. With adaptation parts—like the oil pan, the connection points, and the front accessory drive—the intent is to have a ‘perfect fit’ for each region.” Each geographic region also has a unique software calibration that helps the engine meet driving and emissions requirements.
The North American market launch of the DD15 is scheduled for 2008, followed by Asia in the second half of 2009 and in Europe in the second half of 2010. DD15—a replacement to the Series 60—will be offered in variants from 455 to 560 hp (339 to 418 kW) and 1550 to 1850 lb¿ft (2102 to 2508 N¿m), including dual torque ratings for special applications. In terms of fuel efficiency, the DD15’s advanced combustion systems and the application of turbo-compounding equate to an up-to-5% advantage over a comparable U.S. EPA 2007 emissions certified engine, such as the Series 60, according to Gray. The new engine can be fitted with additional emissions-reduction technology, such as selective catalytic reduction as needed for specific regions.