Cummins unveils 2027 X15 heavy-duty diesel engine
24 March 2026
Cummins unveiled its US EPA 2027-compliant X15 diesel engine at the Technology & Maintenance Council (TMC) Annual Meeting in Nashville, Tennessee.
The 2027 X15 is rated up to 605 hp and 2,050 lb-ft (2,779 Nm) of torque. The engine maintains the familiar X15 architecture and components, “while incorporating refinements that can contribute to improved fuel efficiency compared with the 2024 X15 and maintaining similar diesel exhaust fluid (DEF) consumption,” according to Cummins.
The engine complies with the EPA 2027 emission standards using larger volume SCR catalysts, compared to the current version of the X15, and electric heating of the aftertreatment system.
The EPA 2027 emission standards include an FTP NOx emission limit of 35 mg/bhp-hr, down from the current 200 mg/bhp-hr. While the stadards are under review, the EPA is expected to keep the 35 mg NOx standard in place and relax some other requirements such as engine useful life and emission warranty periods.
To meet the more demanding NOx emission requirements, the SCR is now “built from two parts,” according to media reports. The aftertreatment unit utilizes two electric heaters powered by a dedicated 48-volt alternator. One heater is located before the diesel oxidation catalyst/diesel particulate filter and another one before the SCR segment.
The 2027 X15 engine was designed for stronger performance and “greater fuel economy” but no details were provided.
Electric heating of the aftertreatment system allows to meet low NOx emission limits but introduces a fuel economy penalty during engine start-up and low load operation. An alternative emission technology for meeting the 2027 standards—the light-off SCR catalyst with a dual dosing urea (DEF) system—has been chosen by Daimler and International, and is expected to be widely used in European Euro VII engines. Paccar said it will offer two EPA 2027-compliant engine platforms but technical details were not disclosed.
Cummins first introduced the X15 engine in 2016, ahead of the US EPA 2017 GHG emission and fuel efficiency standards. The X15 replaced the ISX15, which was produced between 1999 and 2020.
Source: Transport Topics