Performance.

Don't be surprised if your drivers start arguing over who gets the new bus with the ISB. It's quicker, quieter and cleaner than every previous Cummins B Series engine. With a high-pressure common-rail fuel system that produces quicker throttle response at every rpm, plus a sophisticated electronic engine control system that optimizes engine timing.

Every ISB engine of 245 hp and above features an exclusive VG Turbo from Holset that constantly adjusts airflow based on engine load, ambient pressure and other conditions. It uses only one moving part, a single sliding nozzle, for exceptional reliability and durability compared to other engine maker's turbochargers, which use dozens of moving parts in an extremely harsh operating environment.

A benefit you might not expect with these higher-horsepower versions of the ISB: They're over 50% quieter on the road, and up to 80% quieter at idle. That's something every school bus driver will appreciate.