Engine Developers Increase Efforts to Decrease Fuel Usage
Clean-sheet engine designs employ revised electronic architectures, mechanical tweaks to boost fuel efficiency and performance of heavy-duty vehicles.
Engineers are leaving no stone unturned in their unceasing drive to improve fuel economy, leveraging electronics, monitoring airflow and using data from outside the vehicle. Computer architectures are being revised to simplify controls and reduce sensor counts, helping keep costs in line. Mechanical changes continue to emerge, but electronics are the key tool for engine design teams that are attempting to do more while using less fuel.
Computers constantly monitor and control the engine, transmission, aftertreatment systems and more. Powerful devices make it possible to analyze huge volumes of data used to adjust engine operations. “These computers are all making decisions multiple times a second to balance making power, saving fuel, reducing emissions, ensuring durability and more,” said John Gibble, performance group manager at Volvo Trucks North America.
“We have thousands of parameters just in the engine that must be calibrated, each one carefully tuned by an engineer,” Gibble noted. “These systems are communicating with each other, reacting to changes in fuel quality, to the weather, to driver habits, to changes in load.” Government regulations for fuel consumption and emissions often provide concrete goals for design teams that race their own corporate demands for improved performance. Engineers are often given simple instructions: improve everything.
“Designing engines to meet U.S. EPA Tier 4 Final and EU Stage V emission standards presents an opportunity to incorporate significant product improvements that enhance torque, increase power density, reduce noise, deliver better cold starting and optimize the benefits of sophisticated electronic controls,” said Tom Carlill, new product introduction program manager at Caterpillar.
Reducing fuel consumption is a primary goal of these improvements, since conserving fuel helps engines meet emissions requirements. It also improves fleet owners’ bottom lines. Data from all systems, including GPS and connectivity systems, is being used by powertrains to trim consumption. “We’ve tackled fuel consumption, which is 30% of the total cost of ownership,” said Stefan Teuchert, senior vice president MAN Truck & Bus SE. “One element of that is map-based cruise control, which saves 10-11% in fuel consumption. In Europe, we plan to reduce fuel consumption for fleets by 50% by 2025.”
When engine and control system developers raced to meet earlier regulatory requirements, many redesigned existing systems. Now, those systems are increasingly being replaced by products that were designed without any direct ties to legacy equipment. “We designed our 13.6-L engine with a clean-sheet approach, meaning we built it from the ground up,” said Kevin De Vries, manager, power system architecture, at John Deere Power Systems. “One of the objectives of that project was to manage in-cylinder efficiencies. We designed this engine for increased firing pressures to accommodate fast fuel burn while minimizing heat losses, leading to increased performance.”
Engine controllers are also being re-examined as engineers look at new ways to utilize the power of today’s powerful multicore processors. One aspect of that is determining whether to distribute intelligence throughout the vehicle or consolidate it in a few powerful boxes. In clean-sheet designs, these decisions are often made with a holistic, full-vehicle approach. “We’ve developed a new architecture with centralized intelligence,” Teuchert said. “There are only six electronic control units in the whole truck. The architecture is open for third-party software, which is new in trucks.”
Sensors monitor a broad range of data points, providing input for control units. Though modern systems require precise information on temperature, pressure and other parameters, engineers have devised ways to reduce the overall sensor count. Virtual sensing, which combines multiple inputs to determine other parameters, is among the techniques for reducing component counts.
“I think we’ll continue to see less reliance on physical sensors as advanced engine control units will enable greater engine control and diagnostics performance,” De Vries said. “We’re currently experiencing a lull in oncoming emissions regulations, meaning we can also focus our resources on refining and optimizing these systems.”
Regardless of where it comes from, the amount of data needed to improve engine operations continues to grow. Many vehicle architectures augment engine inputs, combining inputs from transmissions and external data sources like GPS. Addressing the millions of elements involved in this sort of overall design strategy can only be done by using sophisticated development and testing tools.
Modeling and simulation are tools of this era, letting engineers and programmers try out different ideas to see how little changes help or hinder the drive to meet functional design requirements. “We’re using virtual analysis before we start creating hardware and building the combustion system,” De Vries said. “Advanced modeling allows us to define and optimize the engine subsystems to achieve our performance requirements.”
Not just engine electronics
While powertrain controllers play a major role in the drive to trim fuel consumption, many other technologies also factor in. Mechanical components and other electronic systems help improve overall mileage, and have been adjusted to glean more from every drop of fuel. Chemistries have been changed to reduce friction between components. Developers continue to tweak these technologies to further improve performance.
“We introduced Turbo Compounding in 2017, a form of waste heat recovery that turns excess heat in exhaust into power at the crankshaft, and recently enhanced the Turbo Compound offering with a next-generation model,” Gibble said. “Other incremental improvements have been made to engine systems like the lubrication and cooling systems, as well as friction reduction, adding up to bigger gains.”
Understanding air movement and temperatures has become more important as the role of aftertreatment systems has expanded. “To further reduce engine emissions, we are working to manage airflow through the engine,” De Vries said. “We are evaluating ways to provide warmer exhaust gas to the aftertreatment systems allowing them to work more efficiently.”
Using wireless inputs
Connectivity is rapidly becoming a tool that augments engine and transmission technologies in the battle to conserve fuel and reduce emissions. A growing number of companies are using GPS and traffic monitoring to help powertrains adjust to conserve fuel. Cellular links are nearly as common on new vehicles as GPS links, making it easier for design teams to treat these wireless inputs as inputs for engine and transmission controls. Adjustments can be made before hills and curves by adjusting rpm levels and gear shifts to meet upcoming requirements.
“Moving forward, you can expect to see the reaction being more and more predictive, knowing the route and traffic ahead, and making minor changes to the powertrain control to keep all systems operating in their sweet spots,” said Gibble. “With our integrated powertrains, the sensing of load and grade allow the transmission to be in the right gear at the right time, enabling engine downspeeding and also saving momentum and energy that can be lost if in the wrong gear or if improper shifting events occur.”
Leveraging connectivity for improved fuel economy is just one benefit for powertrain engineers. Vehicle architectures can be altered to improve operations and add predictive maintenance so breakdowns can be avoided and costly remote service calls can be reduced.
“A connected vehicle that is aware of its surroundings via onboard sensors and real-time GPS position data can then anticipate load requirements and continually adjust engine output to maximize overall efficiency,” said Carlill. “There are opportunities to implement more distributed architectures using multiple engine control modules optimized for specific functions. With upgraded telematics, it’s also possible to completely remove such functions from the engine itself and perform them remotely, especially for prognostics.”
In the future, many fleets will turn to 5G cellular technology to get more data so more precise changes can be made. For example, more detailed maps with elevation information could provide enough information to let powertrains adjust for small hills. However, 5G will be a leading-edge technology for a while. “We’re definitely preparing for 5G, but it may take some time,” said Lane Arthur, director, digital solutions, at John Deere. “We’ve still got some users who use 3G connections.”