The Common Rail injection increased power and torque and noticeably reduced engine noise compared to the previous 24-valve Cummins engines. The next step of ISB evolution was in 2003 when the engine was upgraded to a Bosch high-pressure Common Rail fuel injection system. The 24v engine had an aluminum intake manifold, new single-piece red or silver aluminum valve cover for the most comfortable and faster access to the engine components for servicing. Now the ISB engines use electronically controlled fuel systems (Robert Bosch GmbH) and a rotary type Bosch VP44 Electronic Fuel Injection Pump. One of the most recognizable differences is a 24 valve cast iron cylinder head (but still is OHV valvetrain). The ISB engine featured a multi-valve pushrod engine design. The camshaft is installed inside the block. The ISB has forged steel connecting rods, an assembled camshaft, and aluminum pistons featured a symmetrical combustion bowl. It has an identical bore size and piston stroke compared to the 6BT.

24 valve 5.9 cummins rear main seal