Detroit Diesel unveils heavy-duty DD15 engine

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After nearly five years and $1.5 billion in development, the new heavy-duty Detroit Diesel DD15 engine was unveiled Friday, Oct. 19, at the company’s plant in Redford, Mich. The six-cylinder, inline DD15 displaces 14.8 liters and uses a new Amplified Common Rail System, as well as innovative turbo compounding technology, the company says.

The engine is the first in a series of new heavy-duty engines from Detroit Diesel that eventually will cover three displacement categories: 12.8 liters, 14.8 liters and 15.6 liters. The market launch of the DD15 in the Freightliner Cascadia will take place in the second quarter of 2008, followed by the Freightliner Century S/T and Columbia models and the Sterling Set-Back L-Line and A-Line.

The DD15 is part of the new heavy-duty engine platform that ultimately will be manufactured by Daimler Trucks in Germany, Japan and the United States. In time, engines sharing this design will be available in all Daimler Trucks heavy-duty models around the world, including Freightliner, Sterling and Western Star as well as Mercedes-Benz and Mitsubishi Fuso trucks. The new platform eventually will replace four distinct engine series used globally by Daimler Trucks. The platform features 90 percent globally shared parts, and engine development and production are being managed internationally.

The DD15 will be available from 455 to 560 hp and 1,550 to 1,850 lb.-ft. of torque, including dual torque ratings for special applications. The DD15 will be produced at the Redford, Mich., plant, which has been completely refurbished and retooled at a cost of $275 million, the company says.

“The DD15 is a best-in-class engine that embodies what the Detroit Diesel brand is all about: performance and efficiency,” says Chris Patterson, president and chief executive officer of Freightliner LLC, soon to be renamed Daimler Trucks North America LLC.

The DD15 uses exhaust gas recirculation and a diesel particulate filter to meet the 2007 U.S. Environmental Protection Agency emissions standards. It will meet the 2010 standards with the addition of a downstream selective catalytic reduction device. “Instead of revamping one of our current engines to comply with EPA standards, we designed a brand-new platform that takes all of the emissions requirements into account,” says Jim Gray, Detroit Diesel program director for the DD15.

The new engine platform includes four valves per cylinder, two overhead camshafts, a uniquely efficient fuel injection system, turbo compounding technology and fully electronic engine management. The DD15 exhibits up to 75 percent better torque response than the current Series 60 engine, the company says. Torque response is measured by comparing relative times required to reach peak torque levels on demand.

ACRS is the first common rail system that controls the entire injection sequence at any operating point, according to Detroit Diesel. As the highest pressure is only generated in the injectors, the injection processes are extremely stable; this results in quiet, refined operation with low fuel consumption and reduced emissions, the company says.

At the rated engine speed of the DD15, the turbine reaches a rotation speed of more than 40,000 rpm. Power is transferred to the gear drive, and therefore to the crankshaft, via a shaft and a hydrodynamic coupling. This arrangement produces a uniform and smooth crankshaft rotation despite the higher torque, according to the company; additionally, fuel consumption is reduced by up to 5 percent compared with a similarly spec’d Series 60.

During development, more than two dozen units were endurance-tested in the United States, Germany and Japan, running for well over 100,000 operating hours, the equivalent of several million miles on the road. A total of 20 tractor-trailer combinations are currently undergoing road trials in the United States, Germany and South Africa, and jointly have covered about 3.5 million miles to date. Five of the combinations operating in this fleet are intentionally overloaded, tipping the scales at 130,000 lbs., while other test trucks are solo units.

The design of the DD15 is based on six vertically arranged in-line cylinders, with compact dimensions and a length of 56.1 inches. For high pulling power, the DD15 has a bore of 139 mm and a stroke of 163 mm, which leaves stroke reserves for future increases in swept volume, the company says.

The cast-iron crankcase features both horizontal and vertical ribs for added rigidity, with the additional benefit of reduced noise. The total engine oil capacity is 47 quarts. The oil level can be checked using a dipstick or with an available oil level sensor linked to the motor control module. Oil consumption and blow-by losses are minimized by the engine’s rigid pistons and crankcase, Detroit Diesel says.

The turbocharger, turbo compounding unit, starter and the crankcase ventilation are integrated into the crankcase and are arranged on the right (passenger) side of the engine. Grouped on the left for ease of maintenance are the motor control module, oil cooler, a module with fuel filters, the fuel pump and the air compressor.

Detroit Diesel says it has developed an updated version of the Jacobs engine brake, which is integrated into the engine as a design feature, making it both highly effective and quiet in operation. The Jacobs engine brake in the DD15 operates in three stages: In the first stage, the brake acts on cylinders one and two, in the second stage on cylinders three to six; in the third highest stage, the Jacobs engine brake acts on all six cylinders. Maximum braking performance in the DD15 is 500 hp.

As the “brain” of the engine, the motor control module (MCM) not only interprets the driver’s performance requirements via the position of the gas pedal, but also controls and monitors all the engine functions, from the temperature of the intake air to the start and sequence of fuel injection. The control module also uses sensors to continuously monitor such stats as oil level, the position of the crankshaft and camshafts and the rate of exhaust gas recirculation.

Service intervals are every 40,000 miles, and the engine is easy to maintain, the company says. For example, the oil filter, oil filler pipe and oil/water cooler are grouped into an oil module on the left side, with the coolant pump, coolant filter and thermostat installed in the immediate vicinity. Also on the left side, a compact fuel filter module accommodates the pre-filter and main filter, as well as the water separator for the fuel system. Top load cartridge oil and fuel filters are easily accessible and cleaner to change, and they also are more environmentally friendly to dispose, according to Detroit Diesel.

Dual overhead camshafts and integrated engine brake make overhead inspection and maintenance easy to perform, the company says.