Bigger Processors, Smaller Engines
Engine designers are using electronics, networks to downsize engines while upping performance, efficiency and NVH characteristics for heavy-duty applications.
Engine designers are advancing electronic control systems to eliminate components and generate more power from smaller engines. They also are leveraging networks to integrate transmissions, global satellite inputs and navigation to further improve fuel efficiency.
The push to improve efficiency starts in the minutia of combustion and engine design and extends to integration with other vehicle systems. Engineering enhancements also are making cabs quieter as they work to maximize the burning of every drop of fuel.
“Electronics can take the place of many traditional mechanical pieces, so we have integrated or eliminated many of the smaller and more powerful electronic pieces in certain components so you don’t need to have as many mechanical movements,” said Johan Agebrand, product marketing director, Volvo Trucks North America. “Many times, those are the sources for vibrations and noises. And the more compact we make our engine package also leads to more weight savings as well.”
Electronic actuators that respond to changing operating conditions can provide precise control of injection timing and pressure, as well as the correct ratio of fresh air and recirculated exhaust. As electronics advance, engineers also are fine-tuning mechanical components to help engines deliver more power and trim size. Together, all these changes yield more time running at optimal levels.
“Mack has developed piston bowl designs that improve the efficiency of the combustion in each cylinder, robust components that can operate with higher cylinder pressure and higher compression ratios,” said Stu Russoli, Mack Trucks’ highway product manager. “We also have an oil system that can operate on lower-viscosity oils to reduce friction losses, and control strategies that coordinate our integrated engine and transmission package to maximize time spent in the sweet spot for fuel economy.”
Devil in the details
The power of modeling and simulation tools lets engineers dig into the finer points of design. Specialists can focus on seemingly minor factors that can bring major improvements. For example, some members of Deere’s team improved wiring efficiency.
“Proper design and integration can make significant improvements in increasing the overall reliability of the engine and its electronics,” said Ashlee Klingaman, manager, product planning and marketing, John Deere Power Systems. “When designing the 13.6-L engine, we made sure to integrate the electronics and the wiring harness right from the start. The integrated wiring harness is tighter to the engine and protects wiring during assembly and service, improving reliability and reducing vibration.”
Trimming size requirements is a major element in most designs. Developers want to deliver more power from smaller engines. Many different strategies are being deployed. “One way to accomplish that is by precisely controlling the amount of air going into the engine to provide precisely enough to support optimum fuel combustion to provide the most power,” said Pete Moorhouse, product marketing consultant, medium engines, at Perkins. “Our new Tier 4 Final/Stage V C4.4 engines accomplish this with a full electronic wastegate control, twin-turbo air system that delivers increased power density. Customers can downsize from a 7.1-L engine to a 4.4-L engine without sacrificing performance – while gaining the benefits of reduced noise and vibration from the physically smaller engine.”
The integration between engines and aftertreatment systems also is an important element in today’s designs. Sensors must constantly check temperatures and other parameters to ensure that all subsystems tied to powertrains are operating at peak efficiency.
“Our mid-range engines – the Detroit DD5 and Detroit DD8 – come standard with variable cam phasing (VCP),” said Len Copeland, product marketing manager for Detroit products at Daimler Trucks North America. “VCP monitors aftertreatment temperatures and then based on need, can adjust the timing of the exhaust camshaft to open early and release heat downstream to bring temperatures to optimum levels.”
Design teams are leaving no stone unturned in their quest for continued advances. Artificial intelligence is becoming a part of many new programs. “We’ll be able to create AI algorithms that will simulate situations when trying to automate the vehicle that will help the driver adapt to every unique situation,” Volvo’s Agebrand said. “This will also help us in the development of the engine and engine efficiency by creating technology and techniques to control fuel in a more efficient way as well.”
Control signal transmissions
Engine efficiency has been improved by linking engines and transmissions to ensure that rpm levels are as close to optimal as possible. Network links are expanding to navigation and safety systems to boost efficiency and potentially avoid accidents. Information sharing is at the core of all these advances.
“Our latest Tier 4 Final/Stage V engines can broadcast accurate information on the available torque and power at a given moment, which when integrated with a machine controller improves machine productivity,” said Perkins’ Moorhouse. “We also use CAN messaging for the engine components to communicate with each other and the engine electronic control module, which is more robust for calibration purposes than using analog-type controllers.”
More powerful controllers and ever-advancing algorithms let design teams fine-tune basic powertrain links, while also enabling closer links to other systems. These systems let vehicles run at optimal levels to improve mileage and reduce emissions. Changes can be made more often than humans typically adjust, letting drivers focus on other areas.
“Integrated powertrain solutions, like the combination included with the Mack MP8HE package, are engineered specifically to support maximum fuel economy,” Russoli said. “Pairing engine hardware configuration and calibration with automated shift strategies and intelligent software capable of reacting to changes in load, grade, speed and torque demand enables the powertrain to operate as one system rather than individual components and enables prioritization of features that are most important to a customer’s mission.”
Links to navigation systems and their satellite inputs let vehicles adjust to maximize efficiency – for example, slowing for curves and speeding up before hills. Some systems even let vehicles that travel set routes learn where to make adjustments.
“Intelligent Powertrain Management (IPM) is standard with Detroit engines when paired with the Detroit DT12 transmission,” Copeland said. “It monitors GPS data and while in cruise control, it can speed up a vehicle when approaching a hill and then reduce the throttle at the crest to run efficiently over the grade with minimal fuel. Recent improvements to the IPM include more road coverage and a learning feature where no grade is mapped or a grade is changed; the system can learn to adapt and change its response to save fuel.”
Linking multiple systems isn’t just helpful for today’s operations. Integration is a major step towards autonomy, which requires a holistic approach that calls for nearly all vehicle systems to work together. Manufacturers like Volvo are adding safety systems to their powertrain networks. “Powertrains now are integrated with safety systems,” Agebrand said. “The more advanced they have become, the more they can identify vehicles and traffic ahead of them and also potentially behind them.”
Efficiently clearing the air
As powertrain designs evolve, aftertreatment systems are as important as engines and transmissions. Progress moves along similar lines, with more integration and a drive to reduce size. New aftertreatment systems debuted when Deere and Detroit Diesel unveiled their latest engines. Other companies continue tweaking designs to trim space requirements without sacrificing power.
“Our latest Stage V engines have a number of improvements in transparent regeneration and are using the latest SCR [selective catalytic reduction] washcoat technologies to improve the aftertreatment efficiency,” said Perkins’ Moorhouse. “When combined with state-of-the-art calibration, this delivers better performance and gives the customer a smaller, more-efficient engine and aftertreatment package.”
At John Deere Power Systems, the 13.6-L engine was the first to utilize an inline Integrated Emissions Control System. “The inline aftertreatment incorporates the components right into the system rather than utilizing a separate mixing pipe,” said Klingaman. “Improvements in the catalyst and substrate technologies allow for smaller sizes and reduced amount of precious metal. These combined improvements allow for a streamlined aftertreatment design that is more compact, flexible and lower in cost.”
When Detroit reveals its DD15 Gen 5 in 2021, it will unveil a new aftertreatment system and features such as thermo-management control. That will trim 60 lb (27 kg) off the weight of the current version, partially by deploying one diesel particulate filter (DPF) instead of two. The filter uses asymmetric cell technology that will trap more particulates while maintaining high flow levels. Powerful electronic controls enable thermocoasting and asymmetric injection at idle.
“Thermocoasting will be active during a regen and will engage the engine brakes without further slowing the vehicle down when the driver lets off the throttle and begins to coast,” said Copeland. “This will keep heat going downstream and prevent the large temperature swings that occur when power is not being produced, which will then shorten regen duration. Asymmetric injection at idle is an expansion of that technology from the limits we have today. This will cut fuel to select cylinders while powering the others at a higher rate, creating higher temperatures to control unburnt fuel build up. This will also help improve aftertreatment performance while idling.”