The 350hp, 6.7L, Cummins ISB XT diesel engine is based on the 5.9L ISB, and in addition to the boosted displacement, the engine boasts more horsepower and torque (up to 750 lb-ft of torque). The exterior dimensions have not changed. The ISB XT has a higher operating speed (2,600 rpm) and allows for Allison trans-shift logic. The patented variable-geometry turbo has new electric actuation. So far, the engine is destined only for the RV market.
