The benefits to vertical integration vary according to the application. Fuel-conscious on-highway users will witness the greatest return. For example, the Mack Super Econodyne MP8-445SE engine/mDrive/C120 drive axle combination offers an engine that is comfortable cruising at 1,150 rpm at highway road speed. This reduces noise, vibration and fuel consumption. “But it is not as simple as clipping 300 to 400 rpm off the typical cruise speed,” says McKenna. “This involves matching the SE engine to the 12-speed mDrive, allowing the engine to remain at ultra-low rpms for highway cruise speeds, while shifting to 11th gear to maintain a higher road speed when operating on rolling hills, and still be well below typical engine rpms.
“There are certain occasions when the mDrive may actually take over full authority from the engine to maintain optimal performance,” he adds. “This simply cannot occur with different make powertrains.”
Integration allows new solutions
The integration of components allows truck manufacturers to pursue concepts that would not otherwise be possible.
“Volvo’s integrated powertrain allowed the company to introduce our XE exceptional fuel efficiency concept, which improves fuel efficiency by reducing engine rpm at a given road speed — a concept Volvo calls ‘downspeeding,’” says Chris Stadler, product manager, Volvo Trucks. “Fuel efficiency improves by about 1.5% for every 100 rpm of downspeeding. So customers spec’ing the XE package can expect up to a 3% improvement when compared to another overdrive transmission in a similar operation.”
To accomplish these breakthroughs, the components must be designed to work together. “The technology that enables the Volvo engine and transmission to act as one is the outstanding communication we achieve with a proprietary interface,” Stadler explains. “This allows us to give the transmission authority over the engine in some instances, and allows the design to be optimized to a higher level of performance.”
A properly optimized engine and transmission can deliver better fuel economy, better performance and longer driveline component life. This is why Volvo Trucks developed the I-Shift automated manual transmission paired with its proprietary engines. Volvo Trucks will now offer its 12-speed, two-pedal, I-Shift automated manual transmission as standard on all Volvo-powered trucks, including the vocational VHD and VNX heavy-haul tractor.
“I-Shift gives outstanding vehicle performance in challenging off-highway situations and has a number of specialized features to enhance performance in difficult situations,” says Stadler. “These include Power Launch, Rock-Free, Downhill Control, Greatest Possible Downshift and Avoid Shifts.”
In 2012, nearly one in two Volvo Trucks built in North America featured an I-Shift transmission. By using microprocessor technology, integrated sensors continuously monitor changes in road grade, vehicle speed, torque demand, weight and air resistances to place the truck in the right gear per the conditions with smooth and optimum shifts. This operation extends clutch life and service intervals. I-Shift reduces wasted revs and boosts fuel efficiency. It also helps improve driver safety by reducing fatigue and allowing drivers to give their full attention to operating the vehicle.
The I-Shift is a truly interactive product that shifts based on several variables. “We are sometimes asked, what are the shift points of the I-Shift? The I-Shift is not like that popular imported car that simply has a I on the speedometer’s 15-mph mark, a II at the 30 and a III at the 45,” Stadler comments. “The I-Shift knows exactly the performance of the Volvo engine mated to it, and will select shift points based on the whole realm of dynamic inputs.”
An integrated electrical system ties everything together. “The communication between the engine and transmission is important and the electrical integration is a key to successful performance of the engine,” says Stadler. “Volvo engineers develop an electrical platform that closely interacts with all the components within the vehicle. They use that platform to ensure these electronics are communicating the correct information to the transmission so that it can place the engine in the correct gear based on the current road conditions.”