Miserly Power Systems

Engineers push engine, transmission technologies to turn off fuel usage.

October 1, 2019

Terry Costlow

Detroit’s new engine has many fuel-saving features.

Commercial-truck powertrains are doing more with less. Engine developers are adding features that reduce fuel consumption, saving owners money while helping fleets reduce emissions.

Digital technologies continue to transform commercial trucking as powertrain providers devise new ways to eke more from each drop of fuel. Engines now adapt to road conditions, adjusting power and shutting down some or all of the cylinders as demands change.

Electric fans and maintenance monitoring now are being used to help keep engines running at maximum efficiency while using less fuel. Design teams also are refining technologies like start-stop and cylinder deactivation, working to make them smooth enough that drivers barely notice the systems are adapting to the environment.

Engine additions

Detroit’s systems analyze both engine and transmission to maximize efficiency.

The role of sensors and controllers is expanding as engineers continue to push the limits of semiconductor technologies. Powertrain suppliers continue to add features and functions that make engines more miserly.

This fall, Detroit’s Integrated Powertrain with the Detroit DT12 AMT (automated manual transmission) was upgraded with Intelligent Powertrain Management, which adjusts engine operation based on environmental inputs. It can coast more often and skip gears while shifting to most efficiently match power output to driving conditions. Improved maps cover nearly 1 million miles of roadways, helping vehicles navigate efficiently and understand road conditions. The system can be further enhanced with several options.

Active decompression can help reduce vibration in start-stop systems.

“Our electronic fan control reduces fan on-time, which can save 40 hp and reduce fuel consumption,” said Brian Daniels, manager of Detroit Powertrain and Components product marketing. “The controlled water pump has a clutch that can reduce engine loads when conditions allow. With Optimized Idle, when the vehicle is parked, the engine will start and stop depending on outside conditions to maintain in-cab temperatures, which can reduce the amount of idling and preserve battery life.”

Other companies are working to broaden the acceptance of start-stop systems that shut down the engine when vehicles stop temporarily. Suppliers are moving to make start-stop technologies more viable by reducing harsh vibrations that occur when engines shut down. Turning off engines during stop-and-go traffic brings sizable fuel savings, but drivers have been critical of the technology that’s currently available.

“Start-stop has seen lousy acceptance—it’s too jerky,” said Joel Morrow, a fleet driver who’s head of R&D at Ploger Transportation. “Drivers find it annoying and people in sleeper cabs sometimes wake in a start because they think someone hit the truck.”

Jacobs Vehicle Systems is addressing that issue with its Active Decompression Technology (ADT), which reduces the magnitude of engine-shake during shutdown by 90%. It reduces engine wear in addition to conserving fuel.

“ADT works by keeping the engine valves open and the cylinders decompressed,” said Robb Janak, Jacobs’ director of new technology. “When it’s switched on, the engine coasts to a smooth shutdown without causing the cab to shake. When starting up, the engine is kept in a decompressed state, which decreases cranking torque by 40% and allows the engine to spin at up to twice its normal speed for smoother starting, faster priming of the fuel system and decreased wear on components.”

Improved accuracy

Adding sensors and controllers to powertrains also helps to reduce unscheduled downtime, which can substantially improve owners’ profits. The sensors that monitor many parameters within an engine can determine when it’s time for maintenance. As these systems become more sophisticated, the number of parameters and the accuracy of measurements are both improving.

“The Freightliner Cascadia maintenance system can accurately measure when scheduled maintenance is required,” Daniels said. “Detroit Connect monitors the powertrain and when a fault occurs, it notifies the fleet and they can use that info to understand the severity of the fault to plan the right course of action. The new maintenance system will compute optimal maintenance intervals based on actual operating conditions of the vehicle and optimize scheduled maintenance.”

Empty cylinders

Cylinder deactivation can bring major fuel savings.

Cylinder deactivation (CDA) is another technique for reducing fuel consumption. Engineers are working to commercialize systems that shut down some cylinders when full engine power isn’t needed.

Reducing fuel consumption is one of the primary driving factors. Eaton plans to use CDA to increase engine temperatures so catalytic converters run efficiently. When trucks are idling for long periods, most cylinders are blocked off, causing heat to rise in those that are still active.

Detroit is working on a similar program.

“Detroit currently uses asymmetric injection to improve aftertreatment performance, which increases uptime,” Daniels said. “During an over-the-road regen, asymmetric injection varies the amount of fuel supplied to the cylinders to create a higher load and higher temperatures to improve regeneration of the DPF.”

Jacobs is focusing on using CDA to decrease consumption while driving. Preventing the intake and exhaust valves for designated engine cylinders from opening improves fuel consumption by up to 20% at the lowest engine loads and with three of six cylinders deactivated. Testing and validation on real vehicles show a solid product lifetime.

“CDA hardware so far has been demonstrated on seven different heavy-duty engine platforms (covering 9-, 11-, 13- and 15-L engines) and five different heavy-duty truck road tests,” Janak said. “It has undergone 4,300 hours and 45,000 kilometers of durability testing, there have been more than 1.2 billion cycles on CDA components and over 470 million cycles of fatigue and overload testing.”