The Cummins M Series engine is a straight six diesel engine designed and produced by Cummins. It displaces 10.8 litres (659.1 cu in). Introduced as the M11 in 1994, it was built on the previous L10 engine (same 4.921 inches (125.0 mm) cylinder bore, but a longer 5.787 inches (147.0 mm) piston stroke compared to the L10's 5.354 inches (136.0 mm) stroke).
Later M11's received the electronic CELECT and CELECT Plus fuel systems consisting of a gear pump and solenoid controlled injectors. The M11 CELECT Plus became the ISM when Cummins applied its Interact System (hence the "IS" in ISM) to the M11 CELECT Plus in 1998 to further improve the engine. The ISM is available in four different configurations, with slightly different emphasis on maximum power (450 horsepower (336 kW; 456 PS) vs. 500 horsepower (373 kW; 507 PS)) and peak torque