Detroit Diesel Reveals its '27 Emissions Plans

Detroit Diesel, the captive engine brand for Freightliner and Western Star trucks, announced it will meet 2027 exhaust emissions limits with a combination of mechanical and electronic advances that comprise its Gen 6 engines. 

Oxides of nitrogen (NOx), the principal target of the ’27 limits, will be cut to the required 0.035 gram per horsepower-hour, down more than 80% from the current 0.2 gram.

Detroit Diesel Gen 6 attributes

Building on an inline 6-cylinder heavy-duty engine platform that originated in 2007, the Gen 6 products will include a redesigned and simplified fuel system, new injectors, asymmetric intake ports, altered camshaft timing, pre-treatment of exhaust gasses, higher fluid dosing, and a thermal control valve on its DD13, DD15, and DD16 diesels. 

The new 13- and 15-liter models will be available in January 2027 and the Gen 6 DD16 will be available a year later.

Higher use of diesel exhaust fluid ahead of the current dosing chamber will chemically neutralize NOx without resorting to a 24- or 48-volt electric heating grid, as some other engine makers will use, Detroit said. 

How to maintain Diesel Particulate Filters

The thermal control valve will speed warmups and keep engine temperature at proper levels to limit formation of NOx, bolster operation of the particulate filter, and increase fuel efficiency. This will especially benefit engines that operate at varying speeds and experience high idling, as in vocational trucks, the company said.

Pretreatment

The builder’s 1-Box aftertreatment assembly will include a pre-treatment chamber ahead of the current chamber remain about the same size as the current 1 Box system, and thus fit in the same space under the right side of the truck cab. This leaves the back-of-cab area clear for body mounting.

New Detroit Diesel lubrication system

A new lubrication system includes an electronically controlled, variable-displacement oil pump that reduces parasitic loads. That and greater combustion efficiency increases fuel economy, which for on-road trucks could be as much as 3% higher.

Ratings for the Gen 6 DD13, which is popular in vocational trucks, range from 425 to 525 horsepower with torque of 1,750 or 1,850 pound-feet. DD15 ratings go from 425 to 505 horsepower with the same torque. 

The DD16, which is a stroked DD15 aimed at heavy-haul and other extreme duty applications, will have ratings of 560 to 605 horsepower with torque of 1,850 and 2,050 pound-feet.  

Retaining parts from previous models

Using the 20-year-old heavy duty engine platform retains 75% of parts from previous models and helps ensure durability and reliability, Detroit said. Continuous improvement since 2007 – in 2010, 2016, and 2021 – met tougher emissions limits as they were imposed for particulate matter and other exhaust-gas components.

The more stringent ’27 limits deal with pollutants addressed in congressional legislation, so are not affected by the recent rescinding of the 2009 “finding,” that greenhouse gas limits greenhouse gasses are causing climate change with and are therefore harmful to humans.

That finding was made by the Environmental Protection Agency under the Obama administration. The Trump administration’s EPA has contradicted that finding and says Congress can regulate greenhouse gasses if it desires.  

Since its beginnings as the General Motors Diesel Division in 1938, Detroit’s offerings have in recent years expanded to include automated transmissions, drive axles, data telemetry, and electronic safety systems.  It is now owned by Daimler Trucks North America, part of Daimler Truck Group, and is a sister company to Freightliner and Western Star.