GREENSBORO, NC. According to Volvo Trucks North America (VTNA) marketing and engineering executives, the benefits that can be unleashed by selecting an integrated powertrain on a new truck is strengthening the business case for spec’ing automated manual transmissions (AMTs) over manual direct or overdrive gearboxes.
Indeed, the OEM reports fuel efficiency can be boosted up to 3% - in an “evolutionary if not revolutionary” manner - when the OEM’s proprietary I-Shift AMT is joined with a Volvo D13 engine that includes modified software along with taller axle ratios. Those pieces have been brought together to form a new powertrain package dubbed the XE13 (XE standing for “exceptional efficiency”) that is now ready for ordering on new Volvo VN tractor models.
The I-Shift AMT is considered the linchpin of the new efficiency package and is a mandatory component of it.
“We launched our AMT in Europe back in 2001,” Magnus Koeck, VTNA’s vp—marketing & brand management, told Fleet Owner, “and it has been an unbelievable success—accounting for 60% of sales within a few years. The I-Shift launched in North America in ’06 and sales in Volvo trucks already amount to 40%.”
Koeck said having such an integrated and intelligent engine-transmission solution in place enables “our very clever engineers to do some very clever things,” such as putting together the new XE13 fuel-efficiency package.
The XE13 package is an example of “total integration,” Ed Saxman, product manager – powertrain, told Fleet Owner. “Both the engine and the automated transmission know the vehicle’s GCW and grade profile and one [engine or AMT CPU] may have ‘authority’ over the other in certain situations while traveling on the road. The software in the package was developed here specifically to reflect North American highway driving patterns.”
While demonstrating the benefits of the XE13 package’s components—which go beyond fuel efficiency to include hill-hold capability and a quieter cab—Saxman observed that the “high peak torque of 1,750 rpm over a wide operating range provides excellent driveability. There are over 1,400 lbs.-ft. of torque available even at 900 rpm and the Volvo engine brake [retarder] provides excellent retardation even at low RPMs.”
According to Saxman, though, the central reason for being for the XE13 package is to “downspeed” the engine so fewer engine rpms are needed to maintain the same road speed. “For every 100 rpm we cut while staying at the same road speed,” he explained, “it saves about 1.5% in fuel consumed. That’s 1.5% better than running with a direct-drive transmission and 3% better than using an overdrive manual.”
Saxman pointed out that with diesel fuel at $4/gal., a truck averaging 125,000 mi. per year would save $2,080 per year in fuel costs if it was spec’d with the XE13 package.
The XE13 package is rated up to 80,000-lbs. GCW and includes the following components:
- Volvo D13 engine with 425 hp. and 1,750 lbs.-ft. of torque
- Volvo I-Shift overdrive transmission with 0.78:1 ratio
- Axle ratios of 2.64 to 2.69
- Proprietary software that ”facilitates seamless communication” between Volvo’s integrated powertrain components
“With the new package, the engine runs in its sweet spot at any given speed, never straying from its sweet spot at any point from zero through top speed,” Saxman noted. “When cruising at speeds below 60 mph,” he added, ”the intelligent software is designed to prompt the I-Shift transmission to downshift only when necessary for maximum fuel efficiency. Like the song says, the I-Shift software knows when to hold ’em and knows when to fold ’em.”
Volvo Trucks regards the new powertain package as the latest step in fuel efficiency for Volvo customers, which the OEM said are already achieving up to 8% improvements in fuel efficiency over EPA ’07 engines. In November 2009, the OEM noted, the launch of its EPA ’10-certified ”No Regen” engines with SCR technology gave customers a 5% increase and powertrain enhancements and advanced aerodynamics, announced at the 2011 Mid America Trucking Show, add up to an additional 3%.
Source: David Cullen / Fleet Owner
Sep 30, 2011David Cullen | Fleet Owner