The second in what will become a four-displacement family of the Heavy Duty Engine Platform (HDEP) from truck maker Daimler has been unveiled as the DD13 from Detroit Diesel.

At 12.8 liters, this complement to the DD15 launched last fall is shorter and lighter, with power ratings from 350 to 450 horsepower and torque from 1,350 to 1,650 foot pounds.

A new block, head rods and rotating parts mean an engine that is 400 pounds lighter than the DD15, which is itself around 20 pounds heavier than the Series 60 installed in the chassis. With significant weight savings and good horsepower and torque, the 13-liter is targeted at the vocational and bulk operator. It gains some weight savings from its single stage asymmetric turbocharging. At the engine's production launch in January 2009, it will not have turbo compounding like its bigger counterpart. Instead, the area around the rear-mounted accessory drive is kept clear for a rear-mounted power take off (REPTO) which is often required in vocational applications. A front PTO (FEPTO) is also offered.

Later, a turbo-compound version will be offered, which is likely to go to 500 horsepower for on-highway applications.

Like the DD15, the engine's main components are made in different locations around the globe, with connecting rods from DDC's plant in Redford, Mich., heads from Mercedes-Benz foundry in Mannheim, Germany, and block castings from the foundry in South Africa. Machining of the heads and blocks as well as engine dress will be in Redford for the DD13 on the same assembly line as the DD15.

The 12-8liter version of the HDEP will be launched - like the bigger 14.8-liter DD15 - first for the North American market. It will be installed in Sterling first, then Freightliner and finally Western Star, all before 2010. It will replace the MBE4000. which goes away for the next emissions step in January 2010.

Ultimately, the world-wide family of HDEP engines will encompass 10.6-, 12.8-, 14.8- and 15.6-liter displacements. Initial plans called for the top three to be available in NAFTA countries, with the smallest for Europe and Japan. However, there is now discussion about bringing in all four for North America.

The 12.8-liter DD13 has a smaller overall size than its bigger counterpart, accounting for the lighter weight. While looking very similar - around 65 percent of the parts are common - the engine not only has a smaller displacement, but bore centers are closer to make it a shorter engine overall as well. Like the DD15, camshafts are built-up hollow shafts with a rear-mounted camshaft and accessory drive. Blocks are gray cast iron and heads are CGI. The engine is robust - accounting for some of its 2200 pound weight - and has a B50 life of 1 million miles.

Using the same Amplified Common Rail Fuel System (ACRS) as the bigger engine, the DD13 offers exceptional fuel economy, according to company officials. The fuel system has a two-stage pump to lift fuel pressure to the rail that is then amplified to as much as 32,000 psi in the injectors. This, says DDC, means less chance of fuel leakage from the ACRS unit.

The engine is designed for long service with 50,000-mile oil and filter changes. Because of its close similarities with the DD15, most service parts are already at the dealers and the technician training requires only an internet based update over the five-day course for the DD15.

More info: www.detroitdiesel.com/