Cummins goes for big power, low emissions with all-new X-Series heavy-duty diesels
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The X15 Efficiency is expected to account for the bulk of X Series engine sales when Cummins' new engines reach full production starting in 2017 (Photo by Bill Visnic).

Cummins goes for big power, low emissions with all-new X-Series heavy-duty diesels

Calling its new-generation X series heavy duty diesel engines symbolic of a “new era at Cummins,” executives and engineers for the Columbus, IN-based engine maker said the X Series lineup hits the big- and medium-bore market with a combination of class-leading power ratings and the ability to meet federal Phase 1 greenhouse-gas (GHG) and fuel-efficiency standards slated to begin next year.

The 2017 X Series inline 6-cylinder engine line is comprised of the X12 with a 12L displacement and the big-bore X15, a 15-liter version of the new engine platform that comes in two variants, X15 Performance Series and X15 Efficiency Series. The X12 has 350-475 hp ratings; the X15 Performance range runs from 485-605 hp, while the Efficiency variant offers 400-500 hp ratings combined with what Cummins believes will be game-changing fuel-efficiency potential.

But if that’s not enough, Jim Fier, Cummins vice president of engineering, said at a media introduction of the X Series that the new heavy duty diesels also underscore the company’s commitment to reliability, part of a four-pronged initiative to lead the market in performance, fuel economy, uptime and integration with advanced transmission and engine-optimization/tuning technology.

Fier said the X Series engines have seen more than 9 million test miles.

“Inspired by our customers and their business needs, Cummins is delivering the power of great ideas with our next-generation engines revealed today as the X15 Performance Series, the X15 Efficiency Series and the X12 focused on productivity—each optimized for specific duty cycles and applications,” said Srikanth Padmanabhan, Cummins president-Engine Business, in a release.

And perhaps at least as potentially impactful as the X Series design’s melding of power and efficiency, standard for the new engine platform is capability for over-the-air (OTA) engine diagnostics, software updates and even calibration changes that can be initiated by the driver through a compatible in-cab telematics interface.

All three engines will be manufactured at the Cummins Jamestown Engine Plant in Jamestown, NY. Limited-production runs begin in the fourth quarter and will total perhaps 1,400 engines by the end of 2016, with full production starting next January, said Fiers. The medium-bore X12 begins production in 2018.

Big-bore is back

Noting that many have speculated Europe’s trend toward downsized engines and the Environmental Protection Agency’s pending 2017 Phase 1 fuel-efficiency and emissions regulations—and stricter phases to come later—spell the end of the big-bore heavy-duty diesel engine, Lori Thompson, vice-president of marketing, said the X Series design and technology innovations prove large-displacement engines aren’t necessarily doomed by legislation.

“The big-bore is here to stay,” Thompson promised, while Fier said the X15 will be viewed as “the big-bore engine that reignited the market.”

The X15 features a new camshaft profile and revised valve-timing regime to cut parasitic losses during combustion and improve thermal efficiency via improved overall breathing. The X15 also delivers the highest compression ratio in the industry, Cummins said, while employing the Atkinson cycle (extended expansion ratio) during certain load conditions to maximize energy density. Other advances include less-restrictive exhaust-gas recirculation (EGR) cooling and numerous friction-reduction measures in the water pump, lubrication system and other areas. The new X Series engines also continue with Cummins’ variable-geometry turbocharging and XPI direct-injection fueling.

Fier said the differences between the Performance Series and Efficiency Series variants of the new X15 include different injection nozzles and specific software calibration, in addition to other hardware variations the company did not detail at the media introduction attended by Off-Highway Engineering.

Both X15 variants also employ a revised version of Cummins’ single-module aftertreatment system that can be up to 40% lighter and present a 60% smaller footprint. A higher-capacity Diesel Particulate Filter (DPF) can extend the ash cleaning service to as much as 800,000 miles, while the system also includes the company’s most-current Diesel Exhaust Fluid (DEF) doser and a more robust compact mixer design. The result is a more-precise spray pattern that minimizes DEF consumption, Cummins said.

X15 Efficiency Series

Projecting that the X15 Performance Series will account for about 10-30% of total production, Cummins seems to be focusing its launch on the advances the X15 Efficiency Series offers to enhance the competitiveness of the big-bore platform. The company promises at least a 3% fuel-efficiency gain compared with the outgoing ISX base engine and in closed-course testing during the media launch, an optimized-load demonstration revealed fuel-efficiency in a Class 8 chassis that could approach a virtually unprecedented 10 mpg.

In a collaboration with transmission-maker Eaton Corp., Cummins offers the X15 what it calls the SmartAdvantage Powertrain, an optimized engine and automated-manual transmission package that is claimed to deliver a monstrous 20% fuel-economy improvement compared with a similar 2010-model engine alone. Cummins engineers said that at a 120,000-mile annual usage, a Class 8 fitted with the X15 SmartAdvantage package can see up to $7,500 in fuel-cost savings.

A design improvement for the variable-geometry turbocharger enhances dynamic efficiency, while a stronger actuator and impeller boost transient response and substantially improve engine braking at lower rpms, Cummins said. The previous exhaust-mounted fuel injector is eliminated, with thermal control now activated in-cylinder and a thermal recirculation device is added to combat fuel waxing or gelling.

The X15 Efficiency Series also incorporates Cummins’ ADEPT suite of interactive functionality with automated-manual transmissions. The ADEPT system includes SmartCoast and Predictive Cruise Control (PCC) functions, which combine to offer an additional 3% fuel-efficiency boost while requiring little effort on the driver’s part to derive the benefits of the automated functions.

The PCC function, which uses global-positioning system (GPS) data to look as much as 1.25 mi (2 km) down the road to anticipate power requirements, combined with SmartCoast during a behind-the-wheel media demonstration to prove uncannily capable of optimizing momentum and maintaining the set road speed while using the least amount of engine rpm. Predictive cruise control will be “first fit” available for Cummins OEM customers Paccar and Navistar when fitted with an automated manual transmission and will be coming for other OEM truckmakers. The system also can be retrofit to any Cummins engine that is 2013 or newer.

Meanwhile, the company also says the X15 Efficiency Series will deliver “a new benchmark in the industry for lowest cost of maintenance,” projecting an almost 50% maintenance-cost reduction over the first 500,000 mi (805,000 km) when compared to its 2010 engine. Oil-drain intervals for typical line-haul applications are extended up to 50,000 mi (80,500 km), depending on duty cycle—and will extend to as much as 80,000 mi (129,000 km) for trucks running at 6.5 mpg or higher and use OilGuard, a new oil-analysis program to be introduced by Cummins. The X15’s valve-adjustment interval is 500,000 miles and fuel filter change intervals are extended up to as much as 50,000 miles, while the crankcase breather filter now is maintenance-free.

Enhanced uptime is also said to be improved by reducing the X15’s total number of components and simplifying some systems. Durability-focused upgraded components include the camshaft lobes, piston-cooling nozzles and the air-handling system.

X15 Performance

With a rating up to 605 hp and torque that can peak at 2050 lb•ft, the 15-liter X15 Performance Series “provides an ideal power match for heavy-haul, vocational and emergency vehicles,” the company said.

Performance Series incorporates an upgraded, high-flow air-handling system that provides quicker pedal response, enhancing driveability at full payload and during steep-gradient climbing. Peak torque comes across a wide engine rpm range that reduces shifting and improves fuel economy. There is more than 450 hp of engine braking at just 1500 rpm and up to 600 hp at 2100 rpm.

X12 coming in 2018

The medium-bore X12 inline 6-cylinder, available in 2018, will offer the best power-to-weight ratio of any heavy-duty diesel in the 10-16L class, Cummins said. The X12 will encompass power ratings up to 475 hp and generate up to 1700 lb•ft of peak torque from 1000-1400 rpm, which should reduce the amount of downshifting and will improve low-speed lugging ability.

The new 12L engine’s superior power-to-weight ratio is enabled by a weight reduction to 2,050 lb (930 kg); the company said an advanced sculptured-block design removes unneeded mass but maintains high rigidity. Other weight savings come from high-strength composite materials for the oil pan and valve cover.

“During the design process for the X12, we evaluated every opportunity to reduce size and lower weight, but importantly, we achieved this with no compromise to structural strength, so that our next-generation 12-liter comes with all the durability associated with a Cummins Heavy-Duty engine,” said Fier. “We are really excited about how the next-generation X12 will complement our engine portfolio and provide to our OEM partners a compact yet capable engine—an ideal fit for shorter-nose conventional cabs—while very low weight makes the engine a great power solution for sleeper trucks sensitive to front-axle weight,” he added.

Over-the-air capabilities

In what Cummins said is a first for the market, all of the X Series engines’ standard OTA engine programming and customization capability allows almost immediate calibration updates, not to mention discreet calibration changes based on duty cycle: the engine can be operated on a high-power calibration, for example, for a certain haul and reverted to a fuel-efficiency-focused calibration immediately after.

Engineers said downtime related to engine-calibration updates or upgrades will be virtually eliminated; fleets can direct a calibration change to every truck without the need for a dedicated service visit. The OTA functionality also provides for remote diagnostics and maintenance scheduling. The OTA updates are of course highly encrypted and most can be downloaded and applied in less than five minutes, Cummins said, via any compatible telematics interface.

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