Cummins officially pulled back the curtain on its 2027 X15 diesel engine at the ATA’s Technology & Maintenance Council (TMC) Annual Meeting in Nashville.
The new diesel offering joins the Cummins X15N natural gas engine in a lineup Cummins calls HELM (Higher Efficiency. Lower emissions. Multiple fuels).
The 15-liter 2027 X15 offers ratings of up to 605 hp and 2,050 lb-ft of torque and is 7% more fuel efficient when fully integrated with the powertrain, the company claims.
The 2027 X15 features a "clean-sheet" base engine design doweled for precision. Richardson highlighted a major shift to a rear gear train—a move that moves rotating mass toward the flywheel to improve harmonics and balance while meeting strict noise level regulations.
The new engine block is sculpted to add strength only where needed, reducing base engine weight, said X15 Product Manager Kyle Richardson. This weight reduction offsets the larger, more advanced aftertreatment hardware required for 2027 EPA standards, resulting in a weight-neutral system that preserves maximum payload for fleets.
Service-first engineering
For its 2027 X15 diesel engine, Richardson said Cummins focused on lowering the total cost of ownership through simplified maintenance. Cartridge-style filters oil and fuel filters eliminate the environmental waste of traditional metal cans and allow for faster, tool-light service. For the first time on a Cummins 15-liter, an active, rotating Closed Crankcase Ventilation system is used to reduce emissions and oil loss.
Twin module aftertreatment
A standout feature of the 2027 lineup is the Twin Module Aftertreatment (DPF/Dual SCR). This system is designed for maximum installation flexibility and a 50% longer useful life thanks to improvements in catalyst and sensor packaging.
Key highlights of the new aftertreatment system include:
- Electric heating system: Powered by a belt-driven 48V high-output alternator, this system enables on-demand thermal management. By applying heat exactly where and when it's needed, the engine can maintain optimal emissions conversion even during low-load cycles.
- Independent operation: Richardson explained that these "beefy grid heaters" create heat independent of engine load, allowing catalysts to reach and maintain optimal operating temperatures within seconds, even during cold starts or low-load cases like bobtailing.
- Parallel flow SCR: This design maximizes NOx conversion and heat retention while minimizing backpressure and the overall length of the system.
- Serviceability: The modular design allows for the independent replacement of the heater, DOC, DPF, and mixer modules, significantly reducing long-term maintenance costs.
Powertrain integration
The 2027 X15 is engineered to work as a singular unit with the Eaton Cummins Endurant transmission and Meritor axles. This deep integration enables advanced digital features like predictive gear shifting and on-ramp boost, which leverage GPS data to ensure the truck is always in the right gear for the terrain ahead.
An Endurant HD Automated Transmission features new software and hardware specifically engineered for the unique characteristics of the diesel engine.
"The engine and transmission integration results in improved launch performance, better low-speed maneuverability, and smoother shifts when compared to previous generations," Richardson said.
The Endurant HD is capable of hauling up to 110,000 lbs. GCW and features a 750,000-mile lube change interval. When paired with IntelliConnect remote diagnostics, the system aims to virtually eliminate unplanned downtime for long-haul carriers.
