Diesel Engines Meet Size, Power, and EPA Challenges

Alan M. Petrillo

Diesel engine manufacturers are developing engines that generate more horsepower (hp) from the same or smaller size units, all while running cleaner to reduce or remove emissions and to more efficiently provide the most power for vehicle operations.

Diesel Technology

Dave Drehobl, manager of specialty vehicle business for Cummins Inc., says the evolution of technology over the years has radically changed diesel engines used in fire apparatus. “The first emissions regulations dealt with smoke and then nitrogen oxides (NOx),” Drehobl notes. “But, these days unburned hydrocarbons, oxides of nitrogen, and particulates are at near-zero-emission output levels in diesel engines.”

He says that in 2002 the industry was first introduced to exhaust gas recirculation (EGR), which lowered NOx levels. “Engines today continue to use cooled EGR,” he observes. In 2007, the industry was introduced to the diesel particulate filter (DPF), Drehobl says, which brought on the need for both passive and active regeneration. Most recently in 2010, the industry added selective catalytic reduction (SCR) with diesel exhaust fluid (DEF) to its diesel engines.

ISL-9 engine
(1) Cummins offers the ISL-9 engine, compliant with EPA 2010 emission regulations, which features the XPI fuel system, enhanced cooled EGR, a single VGT turbocharger, selective catalytic reduction, and Cummins particulate filter. (Photo courtesy of Cummins.)

“With greenhouse gas fuel efficiency regulations in front of us,” Drehobl says, “what’s happening now is the integration of onboard diagnostics (OBD) into engines, something that has been around since the late 1990s in cars and light trucks.”

Cummins uses an engine control module (ECM) running OBD software in the background that monitors the engine in a real-time diagnostic mode to identify if there is any engine system malfunction, Drehobl says.

He points out that the Environmental Protection Agency (EPA) and the California Air Resources Board expect that an engine will remain in compliance with coming greenhouse gas regulations as it operates. “Our engine control module accomplishes that task as it performs diagnostics on the engine, aftertreatment, cooling system, and the charged air system on the vehicle,” Drehobl adds.

Because diesel engine emissions have been reduced to near-zero levels, regulators are now focusing on improving fuel economy, and greenhouse gases and fuel economy work hand in hand. “Greenhouse gas rules regulate the carbon dioxide (CO2) output from the engine,” Drehbol points out, “and when you lower carbon dioxide emissions, the engine consumes less fuel and the miles per gallon improve.”

ISX-12 engine
(2) The ISX-12 engine made by Cummins was designed to deliver better fuel economy, performance reliability, and durability in a compact design that could save space on fire apparatus. (Photo courtesy of Cummins.)

Durable with Less Weight

Creighton Pritzlaff, Navistar’s vocational sales manager for the North American fire and emergency segment, says Navistar offers its own brand of engines in commercial chassis in a range that includes the Maxxforce-7, Maxxforce-11, and Maxxforce-13 engines. The Maxxforce-13 is available in a 475-hp rating (1,700 foot pounds of torque), two 450-hp ratings (1,700 foot pounds of output and multitorque output of 1,550/1,700 foot pounds), as well as a 430-hp rating (1,550/1,700 foot pounds).

Navistar’s Maxxforce-11 four-cycle diesel engine is rated at 390 hp (1,450 foot pounds of torque) and 365 hp (1,250 foot pounds). The Maxxforce-7 is a 389-cubic-inch 6.4-liter displacement V8 turbocharged diesel (550-660 foot pounds).

“Maxxforce-13 is our newest product and features a high-pressure common fuel rail that uses a high-pressure fuel pump electronically controlled to deliver fuel to individual injectors,” Pritzlaff says. “The system meters the pressurized fuel going into the cylinder for more precise fuel control, better performance, and fewer emissions.”

Pritzlaff notes that the Maxxforce-13 uses a block designed of a compacted graphite iron material that is so strong it allows Navistar to cast a thinner and lighter block yet one that is stronger than cast iron. “This material also absorbs high-frequency energy,” he adds, “so there is less engine noise.”

Maxxforce-7 diesel engine
(3) Navistar makes the Maxxforce-7 diesel engine in a V8 configuration that displaces 6.4 liters with a power output between 220 and 300 horsepower. (Photo courtesy of Navistar.)

The engine also features a dry deck, Pritzlaff says. “The mating surface between the head and the block does not have any oil or coolant passages,” he notes, “so there can be no gasket failure. This adds to the durability of the engine.”

Ultimately, he says, the benefits for fire departments are greater power performance, engine longevity, reliability, and keeping the overall weight of the apparatus down.

Brad Williamson, manager of engine and component marketing for Daimler Trucks North America, maker of Detroit Diesel engines, says its products are available in Freightliner custom chassis and Pierce Manufacturing fire apparatus.

“DD13 is the engine of choice for all fire applications and provides up to 470 hp and 1,650 foot pounds of torque,” Williamson says. “The DD13 features the amplified common rail fuel system (ACRS), integrated Jacobs engine brake, BlueTec emissions technology SCR system, dual overhead cams, and an asymmetric turbocharger.”

The 2013 DD13 model also features a variable-speed water pump and optimized piston designed with a carbon ring scraper ring to deliver more consistent performance and fuel economy over the life of the engine, Williamson points out.

Weight of the DD13, an in-line six cylinder diesel engine, is 2,575 pounds.

Emissions Challenges

The biggest challenge facing engine manufacturers today is designing them to federal vehicle emission standards and still meeting the reliability and dependability standards that are important to the fire service, Pritzlaff points out. And, Navistar has an advantage, according to Pritzlaff, in that it has its own engine, chassis, and multiplex system. “Integrating those elements allows us to control the quality of the whole system,” he says, “so customers get high quality from a single source.”

The U.S. Environmental Protection Agency (EPA) 2013 regulations require the same near-zero emission levels of NOx and particulate matter (PM) as were required beginning in 2010. ODB are also required across the full on-highway product line in 2013. Beginning in January 2014, new greenhouse gas and fuel efficiency regulations will be in effect by the EPA for all heavy-duty diesel and natural gas engines. Further reduction in greenhouse gas output is scheduled for 2016. “There will be a dialogue between the EPA and the industry after that,” Drehbol says. He notes that Cummins elected to combine meeting OBD and greenhouse gas requirements in a single product. “As of January, all of our engines meet the 2013 OBD and 2014 greenhouse gas regulations,” Drehbol says.

He states that Cummins is continuing to look beyond 2014 regulations concerning engine development. “We’re working to reduce parasitic horsepower losses on diesel engines,” he says. “Think about the power it takes to drive a water pump, fuel pump, or the fan in front of the engine, and you see these parasitic power losses,” he comments.

(4) The Maxxforce-13 made by Navistar is available in 475-hp, 450-hp, and 430-hp ratings with torque outputs of between 1,500 and 1,700 foot pounds. (Photo courtesy of Navistar.)

Future Developments

Drehbol says that Cummins is seeking different methods of handling the engine’s cooling system, water flow, power to drive the water pump, as well as the possible electrification of engine subsystems. “Maybe the water pump or air compressor might become electrically operated,” he notes. “In the future, we may have a clutch-actuated air compressor so the engine isn’t driving it all the time.”

Cummins also is focused on continuous improvement in how it manages the combustion process, Drehbol says. “Heat drives an engine’s turbocharger and then goes to the after system,” he observes. “If we can recover some of the heat from the exhaust, we might drive a small turbine to put power back into the crankshaft. Basically, that’s waste heat recovery.”

ALAN M. PETRILLO is a Tucson, Arizona-based freelance writer and is a member of the Fire Apparatus & Emergency Equipment editorial advisory board. He served 22 years with the Verdoy (NY) Fire Department, including in the position of chief.

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