REDFORD, Mich. Detroit Diesel, the long-time No. 1 engine supplier to the motorcoach industry, has officially taken the wraps off the successor engine to the Series 60.

Detroit says it spent nearly five years and more money than any engine manufacturer has ever invested in the development of an engine -- $1.5 billion to bring the heavy-duty DD15 power plant to market. The DD15 displaces 14.8 liters and is a six-cylinder, in-line design.

In announcing the engine, Detroit Diesel said the DD15 is designed to provide "best-in-class fuel consumption, as well as industry-leading power and performance."

To achieve those results, Detroit says the DD15 employs a new "amplified common rail" fuel-injection system, as well as "innovative turbo compounding" technology.

It 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 first vehicles to get the DD15 will be new-model Freightliner trucks in the second quarter of next year. Eventually, it will make its way to the motorcoach industry and ultimately will be manufactured by parent company Daimler Trucks in Germany and Japan.

U.S. production will be at Detroit Diesel's plant in Redford, near Detroit, which has under gone a $275 million renovation and retooling.

The DD15 will be offered in output and torque variants from 455 to 560 horsepower and 1,550 to 1,850 foot pounds of torque, plus dual torque ratings for special applications.

"The DD15 is a best-in-class engine that embodies what the Detroit Diesel brand is all about: performance and efficiency," said Chris Patterson, president and chief executive of Freightliner LLC.

"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, Detroit Diesel program director for the DD15.

According to Gray, early internal and driver testing have shown that the amplified common rail system, low-inertia dual overhead hollowed camshafts and compact, simplified turbocharger help give the DD15 up to 75 percent better torque response than the current Series 60 engine.

The torque response was measured by comparing relative times required to reach peak torque levels on demand.

Initial testing has included more than two-dozen units conducting endurance runs in the United States, Germany and Japan, compiling more than 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 U.S., Germany and South Africa, and have jointly covered

nearly 4 million miles.

The compact design of the DD15 is based on six vertical in-line cylinders with an overall engine length of 56 inches. The total engine oil capacity is 47 quarts.

Grouped on one side of the engine are the turbocharger, turbo compounding unit, starter and the crankcase ventilation. Grouped on the other side are the motor control module, oil cooler, a module with fuel filters, fuel pump and air compressor.

Normal service intervals are every 40,000 miles. The oil filter, oil filler pipe and oil/water cooler are grouped into an module on the left side of the DD15, with the coolant pump, coolant filter and thermostat installed nearby. Also on the left side, a compact fuel-filter module that accommodates the pre-filter and main filter, as well as the water separator for the fuel system.

Detroit Diesel has developed an updated version of the Jacobs engine brake, which is integrated into the engine, improving effectiveness and making it less noisy, says Detroit.

The Jacobs engine brake in the DD15 operates in three stages: in the first stage the brake acts on cylinders one and two and on cylinders three to six in the second stage. In the highest stage, the Jacobs engine brake acts on all six cylinders. Maximum braking performance is 500 horsepower.