| MPI MP21B | |
| Powertype: | Diesel-electric |
| Builder: | MotivePower |
| Builddate: | 2008 |
| Buildmodel: | MP21B |
| Cylindercount: | I6 (×3) |
| Primemover: | Cummins QSK19C (×3) |
| Enginetype: | Straight-six engine |
| Aspiration: | Turbocharger |
| Poweroutput: | 2100hp |
| Totalproduction: | 1 |
| Operator: | Amtrak |
The MPI MP21B is a low-emissions diesel switcher locomotive built by MotivePower. It is powered by three Cummins QSK19C I6 engines with each one developing 700hp and creating a total power output of 2100hp. One MP21B locomotive was manufactured,[1] currently operated by Amtrak.[2]