Combustion Engines Carry on in Construction

Diesel engines continue to evolve to stay relevant while the industry intensifies its pursuit of zero emissions.

Cummins’ B6.7 Performance Series illustrates the evolution diesel engines have undergone, delivering far better performance and near-zero NOx and PM emissions. Stop-start capability aids fuel savings of 5-15% depending on duty cycle. (Cummins)

A recent virtual panel discussion reminded me that we ought not forget the propulsion workhorse of our industries: the good ol’ diesel engine. It’s sometimes easy to forget in the avalanche of EV and fuel-cell developments – many of them detailed on this website – that combustion engines will continue to power the majority of on- and off-highway heavy vehicles at least for the next decade. To further improve ICE efficiency during this powertrain-diversification process, engineers and R&D departments are still plugging away (pardon the pun) on engine and fuel advancements.

Volvo sees an eventual shift to a majority of battery and fuel-cell electric propulsion for machines, trucks and buses, but internal-combustion engines using alternative fuels will still have a place. (Volvo)

“For most of the sectors of the construction industry, diesel is the technology of choice particularly for the largest construction machines and equipment,” said Allen Schaeffer, executive director of the Diesel Technology Forum, which hosted the virtual event with industry leaders. “The energy density of the fuel, diesel’s ability to deliver high power demands that serve the functions of construction activity. But diesel is still evolving, and it will continue to do so in the future with even lower emissions and greater efficiency.”

Decarbonizing sectors such as construction is already possible by expanding the use of low-carbon biodiesel fuels, the experts agreed. Ray Gallant, VP of product management at Volvo Construction Equipment, stressed that there is no single solution. “So, battery electric on the small equipment is a fairly easy transition to make. We’ll follow that up with fuel-cell electric, where you generate your electricity on board through a hydrogen fuel cell. But there’s always going to be a place for internal-combustion engines using alternate or low-emission fuels,” he said. “We think it’s going to be a combination of all those things going forward.”

Cummins’ construction market director Jeremy Harsin provided some perspective on the reality that many fleets are still burning diesel at the lower-tier levels. “It feels a little weird to still be talking about Tier 3 product [from the 2006-2011 timeframe],” said Harsin. Due to the longevity of construction equipment in the market – up to three times the life of on-road vehicles – “this Tier 3 population is still very relevant and definitely is going to offer an opportunity to reduce emissions just through natural fleet turnover as we move forward.”

A major trend in the industry is having multiple injections and digital-rate shaping (DRS) via injections to shape the heat release rate on the engines, according to Bosch’s Alex Freitag. (Bosch)

“We’ve painted ourselves into a tight little emissions box [Stage V emissions but dual-certified for U.S. and Europe] that we call ‘near-zero-emissions’ diesel,” Harsin continued. For its Performance Series engines introduced in 2018, Cummins moved beyond “just the architectural bits” and started to add more advanced features like stop-start technology. “That’s going to be representative of what’s coming out in any new equipment that would serve a Western market,” he said.

The fuel system continues to be an important part of the equation, said Alex Freitag, Bosch’s director of diesel systems engineering. “The trend that we see in the industry is having multiple injections and digital-rate shaping (DRS) via injections to shape the heat release rate on the engines,” he said. “We also have now more emphasis on NOx raw emissions during cold operation as the cold phase gets more and more important. And temperature management becomes one of the key parameters to really keep emissions under control under all conditions.”

One promising measure often applied to on-highway vehicles but also suitable for off-highway, according to Freitag, is 48V systems. “Everybody thinks of fuel-consumption improvement with 48-volt systems, but it can also help with EGT [exhaust gas] temperature management,” he said. “The 48V system can be used to increase the load and therefore have that temperature catalyst which is critical to meet emissions.”

Beyond “compression-ignition product renewal,” including the use of renewable fuels and biodiesels, the potential adaptability of spark ignition within a diesel engine should be further explored, said Jon Gilbeck, John Deere’s global manager of construction equipment product marketing and planning. A spark-ignited engine increases renewable-fuel options, he noted, and reduces aftertreatment complexity. Propane, green hydrogen and ethanol are some options, listed from lower to higher viability, as is hybridization where it makes sense.

“There’s multiple paths that need to be explored to see what might be viable, where it fits with the infrastructure, and frankly get to more of a mass adoption,” Gilbeck said. “We recognize that customers are not necessarily attuned to say, ‘I want two, three, four different fuel types on my job site.’”

The best path forward achieves the goal of zero emissions by 2050, Harsin said, “implying more of a rational, gradual phase-in as [technologies] start to make sense.” That’s plenty of time for combustion engines to continue to evolve and make a positive impact.