DETROIT — After nearly five years and $1.5 billion in development, the new heavy-duty DD15 engine was unveiled last week at Detroit Diesel’s Redford, Mi. engine plant. The engine will make its NAFTA market appearance first in Freightliner Cascadia models, beginning in April 2008, followed by Century S/T and Columbia models and then the Coronado, Western Star, and Sterling L-line and A-line models later next year.

It’s a platform that will eventually be shared among all Daimler Trucks worldwide, including Mercedes-Benz trucks built in Europe and Mitsubishi Fuso trucks in Japan. This engine platform will replace the four distinct engine series used today by Daimler Trucks brands globally. It will be manufactured by Daimler Trucks plants in Mannheim, Germany and Kawasaki, Japan as well as Redford.

The new engine is an in-line 6-cylinder engine with four valves per cylinder and two overhead camshafts that was born EPA-’07 compliant (via cooled EGR and a particulate filter) and is ready to meet EPA ’10 with the addition of just a downstream selective catalytic reduction (SCR) exhaust aftertreatment system to meet the lower NOx standards. The engine platform will first be offered in a 14.8-liter displacement, the DD15, later in 12.8 and 15.6 liter models – the DD13 and DD16 respectively — with modifications only to the cylinder liners. Everything else on the engine will stay the same. All three displacements will have 90 percent globally shared parts, and engine development and production will be managed on an international level to further facilitate efficiencies.

The new engine will be offered in variants from 455 hp to 560 hp and 1,550 to 1,850 lb ft in its initial 14.8-liter trim. When the 15.6-liter comes out in 2010, it will get up to 630 hp and 2050 lb ft. The 12.8-liter version, the DD13, will eventually replace the MB4000, with torque ratings between 1,250 and 1,650 lb ft.

This engine isn’t at all a re-purposed and repackaged Series 60, which is now 20 years old. It’s a brand new, clean-slate design that incorporates a number of performance-improving enhancements. Chief among them is the Amplified Common Rail System (ACRS) that optimizes combustion efficiency and reduces noise dramatically.

As well, Turbo Compounding adds “50 free horsepower to the engine,” Detroit Diesel says. There are two turbos on the engine, the first to function in a traditional air-management capacity to boost intake pressure, while a second turbine wheel is linked by a viscous clutch directly to the engine’s rear gear train. Exhaust spins the second turbine wheel, adding that much more power the total output of the engine.

The DD15 exhibits up to 75 percent better torque response than the current Series 60 engine, Detroit says, spooling up to rated torque in just 1.5 seconds instead of over 4 seconds. It’s said to be only 150 lb heavier (in chassis weight) than the Series 60.

During development, the DD15 was subjected to intense trials under the most extreme conditions. 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 have jointly 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 lb. Currently 12 trucks are in fleet hands.

Detroit’s current engines, the Series 60 and the MBE4000, will be available until 2010, when they’ll be phased out. The DD15 will become available in the U.S. in April 2008, in Asia during the second half of 2009, and in Europe in the second half of 2010.