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  • The Next-Generation, Heavy-Duty Truck Engine, The Cummins X15

The Next-Generation, Heavy-Duty Truck Engine, The Cummins X15

The next-generation heavy-duty truck engine that is raising the bar for power and fuel economy

John Lehenbauer
Nov 3, 2016
Photographers: Courtesy of Cummins
With emissions standards for over-the-road truck engines becoming more stringent every year, meeting the ever-changing regulations forces diesel engine manufacturers to push the technology envelope even further. The complicated emissions systems employed by engine makers compromise fuel economy and power in order to meet the restrictive tailpipe regulations.
So, when Cummins updated its tried-and-true ISX15 engine series, the company didn’t make concessions for any aspects of the new engine’s performance. Instead, engine developers worked from the perspective that all the systems and components should be engineered and refined to complement each other. To accomplish this, the engineers retained the best attributes of the ISX15, and then made the improvements and refinements that allow the engine to achieve the greater fuel economy, power output, and durability they desired. The all-new Cummins X15 turbodiesel engine is the result of those innovations.
The X15 features a new, optimized cam profile that minimizes parasitic loss during combustion and increases thermal efficiency. This optimization supports the engine’s higher-than-normal compression ratio, which initiates a cleaner burn. The piston design handles the higher compression and reduces heat transfer (from combustion) to the engine oil. This reduction in the oil temperature slows the fluid’s thermal breakdown, helping extend normal service intervals from 25,000 miles for the ISX15 to 35,000 miles.
The X15 also features a variable-geometry turbocharger with a stronger actuator and a redesigned impeller that provides rapid boost and improved engine braking (up to 600 brake horsepower at 2,100 rpm).
Photo 2/3   |   Cummins’ new X15 Performance engine replaces the company’s ISX15. This state-of-the-art, over-the-road truck engine meets today’s strict emissions standards while providing more power and better fuel economy than the previous model.
Cummins Xtra-High Pressure Injection is a common-rail fueling system that’s highlighted by multiple injection events per cycle, which facilitates smoother, quieter operation and helps improve mileage. Steel plungers and a diamond-like coating on the roller tappets of the injectors are used for greater durability.
All these innovations coupled with Cummins’ Single Module Aftertreatment system allow the X15 to exceed the U.S. Environmental Protection Agency (EPA) 2017 greenhouse gas and fuel-efficiency standards.
The X15 is available in two different configurations: Performance and Efficiency. Each series is designed to fill a niche in the truck-engine market. The Performance-series engine has a power range of 485 to 605 hp, with 2,050 lb-ft of torque. It is well suited for heavy-haul, vocational, and emergency vehicles. On the other hand, the Efficiency Series, with its 400 to 500 hp and 1,850 lb-ft of torque, is better for meeting the needs of regional-haul and line-haul applications for which greater fuel mileage is important.
The X15 Efficiency’s enhanced fuel mileage is a result of the Cummins and Eaton SmartAdvantage Powertrain, which precisely adjusts the engine to vehicle weight, road grade, and driver input through throttle position, thus reducing fuel consumption. Cummins’ ADEPT system—a suite of advanced electronic engine-control features (including SmartTorque2, SmartCoast, and Predictive Cruise Control) that interact with automated manual transmissions—helps drivers operate as efficiently as possible by making minor adjustments to speed, power, and gear selection to accommodate for changing road conditions.
Another item that received attention during the X15’s development is the reduction of power-robbing friction. Eliminating as much drag as possible frees up power. So, to lessen the amount of drag, a low-friction water pump, geartrain, oiling system, pistons, and exhaust gas recirculation (EGR) are employed on the X15.
Of course, Cummins would never release any of its technology without performing extensive tests first. So, before the X15 went into full production, more than 9 million miles of field testing (all of them logged in real-world driving situations) were performed on the new engine, with every component being thoroughly scrutinized before the powerplant received its final approval.
Photo 3/3   |   Cummins X15 Front Valve Timing Cover
SPECIFICATIONS
Engine: Cummins X15
Displacement: 15.0L (915ci)
Engine Layout: I-6
Valvetrain: DOHC
Bore x Stroke: 5.39 x 6.65 inches (137 x 169 mm)
Compression Ratio: 18.9:1
Head material: Iron
Block material: Cast iron
Piston material: Forged steel
Power: 605 hp at 1,600 rpm
Torque: 2,050 lb-ft at 1,100 rpm
Induction: Variable-geometry turbocharger
Exhaust: Cast-iron manifold
Intercooler: Air-to-air
Cooling System: Liquid cooled
Fuel System: Xtra-High Pressure Injection (XPI) common-rail, direct injection
Lubrication System: Wet sump
Lubrication Capacity: 52 quarts
Dry Weight: 2,961 pounds
Length: 55 inches
Width: 38 inches
Height: 49 inches

Sources

Cummins
Columbus, IN 47202
1-800-343-7357
http://www.cummins.com
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