Engine and Drivetrain Efficiency Drives Down Fuel Use and Emissions in Construction Equipment



CE EnginesThe construction equipment industry has been making steady improvements in the areas of fuel efficiency and emissions ever since the EPA began regulating non-road engines in 1996. Four key advancements have enabled the gains:

  • Evolution of the diesel engine
  • Increased efficiency in the hydraulic system
  • Better integration between engine and drivetrain
  • Emerging technologies that help reduce unnecessary fuel use

AEM’s new report, Benefits of Construction Equipment Technologies and their Impact on Society, highlights the many achievements of the past several decades. Equipment manufacturers and their Tier 1 suppliers have worked collaboratively to not only meet EPA requirements for fuel efficiency and emissions, but actually exceed them.

At each stage of the EPA’s emissions mandate, the construction industry gained another 3-5% in engine efficiency. At the conclusion of the fifth and final stage, Tier 4 Final in 2015, construction equipment was now 11-15% more fuel-efficient than in 1996. Furthermore, construction equipment has seen a 96% reduction in NOx and DPM (diesel particulate matter) emissions per gallon of diesel fuel consumed. There has also been an 11-15% reduction in CO2 emissions per machine hour.


Jeremy Harsin

“When you’re talking about construction equipment, you’re talking about things that are reasonably complex. You can design the best engine ever, but if the equipment manufacturer doesn’t understand how to engineer it in to get the most out of it, it’s a lost opportunity.” - Cummins' Jeremy Harsin


Let’s put that in perspective. The emissions generated by 25 wheel loaders in 2020 was equivalent to what a single wheel loader generated back in 1990. But the wheel loader isn’t the only piece of construction machinery that has become significantly cleaner and more fuel-efficient over the past 30 years. Considering the massive amount of diesel-powered construction machinery utilized in North America alone, the fuel saved is equivalent to taking 1.35 million cars off the road permanently.

There is no disputing the fact that construction equipment has come a long way over the past few decades. While the catalyst may have been regulation, the enduring motivation has been much more.

“When looking back over the time horizon of the EPA requirements, it’s important to understand that so much machinery had been designed when fuel was really cheap,” said Ben Hoxie, senior engineering director - solutions at AEM member company Danfoss Power Solutions, a provider of mobile hydraulic and electrification products. That started to change as the industry navigated its way through the various stages of the EPA mandate. “The regulatory push for less emissions was eventually accompanied by an economic push to be more efficient,” Hoxie added.

Closer Collaboration Leads to Complete Powertrain Efficiency

The first series of steps involved the evolution of the diesel engine. A major leap forward was taken around 2005 when the shift from mechanical to electric took place. “Brilliant combustion engineers were focused on gaining more control over the fuel system and optimizing fuel economy,” said Jeremy Harsin, global construction market director at AEM member company Cummins, a manufacturer of construction engines.

Some additional leaps were taken in the 2011-14 timeframe. Aftertreatment systems were now coming into play, helping to dramatically reduce exhaust emissions. Harsin said other system-level improvements were also being developed to make engines more efficient. The combination of high-pressure common rail fuel delivery systems, electronic fuel injection and turbochargers enabled engines to pump out more horsepower per cubic centimeter of displacement, a concept known as power density. In other words, smaller and lighter engines were now capable of doing the work of their larger predecessors.

“What’s really important is the full shape of the torque curve,” Harsin said. “The amount of torque you’re able to provide through the entire RPM band is really important with construction equipment. Take an excavator, for instance. It doesn’t run at the full rated point; it’s typically in that mid-RPM range. Front-end loaders want as much torque as they can get on the low end. Given that, a big piece to the efficiency gains has been matching torque curve to the application at hand.”

Another big piece has been closer collaboration between the manufacturers of equipment, engines and hydraulic systems.

“When you’re talking about construction equipment, you’re talking about things that are reasonably complex,” Harsin said. “You can design the best engine ever, but if the equipment manufacturer doesn’t understand how to engineer it in to get the most out of it, it’s a lost opportunity. As an engine manufacturer, we like to think through the entire driveline to find the best solutions. For example, an innovation like engine downspeeding pairs really well with something like a CVT transmission in a wheel loader. As an engine manufacturer, we're really making power at a speed and torque at a speed. Knowing how best to integrate everything has really been key."

Advancements in hydraulic systems have also played a role by helping improve the work function efficiency of construction equipment.

“You need hydraulics to transfer a lot of power to remote areas on a machine,” said Ben Holter, director of automation systems at Husco, a manufacturer specializing in hydraulic and electro-mechanical control systems. “We’ve done a lot of research and testing dating back 20 years. We’ve learned a lot about where the efficiency losses are in terms of fuel used and dirt moved. We’ve focused on where we can improve efficiency in those areas, while also ensuring that productivity and operator comfort are still there.”

A relatively simple solution could be identifying areas of a machine where slightly oversized hydraulic valves could help reduce efficiency loss. Similarly, changing cylinder sizes to better match the work function can result in less compensation loss. On the more complex end of the spectrum, an equipment manufacturer could move from an open-center system to a pressure-compensated load-sensing system, which allows for variable flow for increased efficiency. A manufacturer could also switch from a pump-and-valve architecture to a software-driven system. In any event, close collaboration between the equipment manufacturer and its Tier 1 suppliers has been vital to ensuring the best, most cohesive solution available is implemented.

Mobile Computing Changes the Game

Thanks to an ongoing evolution in software and mobile computing, today’s control systems are more sophisticated, intelligent and efficient.

“What we can do with modern software is not even a comparison to years ago,” Hoxie said. “And when you look back, the emissions regulations really forced computers into the engine space. That opened up the industry to being more comfortable with mobile computing in general. With comfort level and fuel cost both increasing, you gradually began seeing more interest and adoption.”

The impact of software-based drivetrains has taken efficiency to another level. “There are always improvements in core science, materials and manufacturing,” Hoxie said. “But so much of what has happened ties to having better control of a machine.”

According to Holter, changing out hydro-mechanical controls for electric controls eliminates efficiency losses associated with simply controlling the system. Electronics also opens the door for things like independent metering and energy recovery to further improve efficiency.

Software-driven controls also make equipment operators more efficient. As Hoxie explained, tasks like loading material into a bucket take a lot of skill. An intricate package of valves, sensors, software and a controller make those types of tasks smoother for the operator. That results in optimum control of the boom and bucket, which leads to more material moved per trip, fewer trips and less fuel consumed.

Software-based drivetrains also make the machine propel function more efficient. These ground-drive systems can sense power needs, and they adjust the engine speed and hydrostatic transmission accordingly to optimize efficiency.

“It’s a pretty advanced computer-control system,” Hoxie said. “Communication between the driver, engine and machine help ensure that the drivetrain is efficiently creating that engine energy and transmitting it to the ground. By having the hydrostatic transmission and engine work closely together, you improve the feel and controllability for the operator. You also improve how much fuel is burned to move the machine around. Fuel-efficiency gains can generally be in the 25-40% range with a system like this.”


Ben Holter

“You need hydraulics to transfer a lot of power to remote areas on a machine. We’ve done a lot of research and testing dating back 20 years. We’ve learned a lot about where the efficiency losses are in terms of fuel used and dirt moved. We’ve focused on where we can improve efficiency in those areas, while also ensuring that productivity and operator comfort are still there.” - Husco's Ben Holter


Other computer-related innovations have also played a role in reducing fuel use. For instance, idle shutdown timers can turn an engine off during periods of excessive idling. “We’ve seen some real-life data where a wheel loader was idling 30-44% of the time it was running,” Harsin said. “That meant 15-20% of the fuel it was burning was when the machine was doing nothing. Features like idle shutdown present a big opportunity to pick up some additional fuel-efficiency gains.”

Another innovation known as telematics presents even more opportunity. Telematics started to become more accessible around 2013. It is fairly common today, delivering real-time engine data so equipment managers can monitor things like idle time.

“Thanks to telematics, equipment managers can work with equipment operators to help ensure that equipment isn't running unnecessarily," said Carlton Bale, director of digital strategy and product planning at Cummins. “Telematics also makes the integration of other engine features more accessible to an equipment manager. In the past, you had to take a machine to a dealer to have features like idle shutdown adjusted. Today with telematics, it’s all doable from anywhere using a connecting interface.”

The bottom line is simple. Construction equipment has come a long way over the past several decades. The efficiency and emissions achievements have resulted from a combination of brilliant mechanical engineering, the leveraging of technology and close collaboration between manufacturers. That same level of collaboration continues today, helping ensure that equipment will continue getting better, safer and more efficient—well into the future.

Want to Learn More?

The Association of Equipment Manufacturers (AEM) released a study outlining how construction equipment technologies have advanced the construction industry and benefited a wide range of stakeholders, from contractors, to owners, to society as a whole.

The Benefits of Construction Equipment Technologies and Their Impact on Society details four construction equipment technologies that play critical roles in advancing the industry, and thereby enabling benefits to productivity and performance, planet and environment, as well as people and safety. For more information, visit aem.org/insights.

In addition to Engines & Drivetrains, Machine Telematics and Machine Control are two other innovations that have helped transform construction equipment over the past two decades. A fourth innovation, Digital Control Systems, will be featured in coming weeks.

Subscribe to the AEM Industry Advisor for more AEM member perspectives. 


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