The MP21B is very similar in appearance to the MP14B shown above.
(Charles Fulton, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)
MPI MPEX SWITCHER MP21B
The MPI MP21B is a low-emissions diesel switcher locomotive built by Motive Power. It is powered by three Cummins QSK19C I6 engines with each one developing 700 horsepower (522 kW) and creating a total power output of 2,100 horsepower (1,570 kW). One MP21B locomotive was manufactured, currently operated by Amtrak.
Appearance
The MP21B looks very similar to the MP14B (see link below for actual photo of unit).
See photo here: https://pin.it/5Y8QT5S
MPI MP21B Overview
Type and origin
Power type: Diesel-electric
Builder: MotivePower
Model: MP21B
Build date: 2008
Total produced: 1
Specifications
Gauge: 4 ft 8+1⁄2 in (1,435 mm) standard gauge
Prime mover: Cummins QSK19C (×3)
Engine type: Straight-six engine
Aspiration: Turbocharger
Cylinders: I6 (×3)
Performance figures
Power output: 2,100 hp (1,570 kW)
Career
Operators: Amtrak