Shortly after celebrating its 20th birthday, Detroit Diesel has announced it will be putting the Series 60 engine out to pasture to make room for a new offering the company said offers improved fuel efficiency, performance and overall quieter operation.

In what the company dubbed the most significant new product announcement of the millennium, Detroit Diesel introduced its new DD15 engine at a recent press event in Michigan. The DD15 will serve as Daimler Truck’s new global engine, with 90% parts commonality around the world.

The very first DD15s will go into Freightliner Cascadia tractors beginning in the second quarter of 2008. They will then be rolled out to the Century S/T and Columbia as well as the Sterling Set-Back L-and A-Line trucks. It will be available in Western Star and Coronado trucks in the third quarter of 2008.

The DD15 – a 14.8-litre, six-cylinder in-line design – will be complimented by a 12.8- and 15.6-litre offering which will round out the DD engine family by 2010.

The Series 60 and MBE-4000 will be retired from the North American highway market by 2010, company officials said.

“The DD15 is a best-in-class engine that embodies what the Detroit Diesel brand is all about: performance and efficiency,” Chris Patterson, president and CEO of Freightliner LLC announced. “With the DD15, a trucker gets the best of everything. This engine provides impressive fuel economy above today’s industry leader while delivering more muscle at a lower horsepower. It’s efficient and powerful.”

The DD15 will be available with horsepower ranging from 455 to 560 with 1,550 to 1,850 lb.-ft. of torque. The engine is designed to accommodate current and future global emissions standards, and can be easily fitted with Selective Catalytic Reduction (SCR) equipment, the company announced.

“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,” said Jim Gray, program director for the DD15. “The result is an engine that offers both power and fuel savings in an EPA07-compliant package.”

The DD15 features a new Amplified Common Rail Fuel System (ACRS) which delivers an unconventional torque curve that points due north upon throttle application, and then stays there. Detroit Diesel officials say the new engine provides 75% better torque response than the Series 60.

David Siler, director of marketing with Detroit Diesel, pointed out it takes just over four seconds to reach peak torque with the Series 60. By comparison, the DD15 reaches the same pulling power in just 1.5 seconds, he said.

“That provides a sensation of commanding the immediate acceleration and power of a much larger displacement engine, but without sacrificing the fuel economy that usually comes with it,” Siler explained.

“The DD15 maintains its peak torque for an amazingly wide band of 600 RPM.”

The ACRS fuel system allows the company to more precisely measure and disperse fuel, explained Siler.

“This allows Detroit Diesel to literally construct a unique personality for every compression, power and exhaust stroke of the DD15,” he said. “We can now control injection not only stroke to stroke, but also within each stroke and even shape the spray patterns within each cylinder.” ACRS is coupled with a new, simplified, non-variable geometry turbocharger that allows for turbo compounding. Siler explained the new turbo “doesn’t require variable geometry or other moving parts to control its rate of spin and boost.”

Because it can spin up to speed and boost faster than VGTs, Siler said the engine delivers a faster response time and improved fuel mileage.

“Traditional engines convert diesel fuel into heat which drives pistons and turns a crank, eventually turning the wheels of a truck,” Siler explained. “In the process, about a third of the entire amount of energy produced from the combustion of diesel becomes wasted exhaust energy. The turbo compounding system literally takes a portion of that previously wasted exhaust gas and routes it through a turbine wheel that transfers it into productive power at the flywheel.”

By recapturing this previously wasted energy, Detroit Diesel officials say the DD15 delivers about 50 “free” horsepower compared to non-turbo compounding engines.

Siler emphasized the improved performance does not come at the expense of fuel mileage. In fact, the company insisted field testing has shown its DD15 is delivering 2-5% better fuel mileage than the Series 60, thanks to the new fuel system and turbo compounding. The best fuel economy improvements so far appear to be occurring while under heavy load, said Siler. A 5% improvement in fuel economy translates to an annual savings of about US$3,600, based on 144,000 miles per year at 6 mpg.

“Customers will finally be able to own an engine that is incredibly fuel efficient but also amazingly powerful and a pleasure to drive,” said Siler. “For the first time ever, the objectives of improved fuel economy and improved power are not mutually exclusive.”

The DD15 is also quiet (about 31% quieter) thanks to its robust construction and cast iron crankcase as well as the new fuel system which inherently runs quieter.