MPI MPXpress

Motive Power, Inc., as the successor company to Morrison-Knudsen or MK Rail, offered a range of passenger diesel locomotives from 2003 that were intended for commuter service. These were four-axle diesel-electric locomotives with a streamlined head shape on one end. Initially, power was provided by the sixteen-cylinder two-stroke engine from the 645 series from EMD with 3,600 hp. 

The first two models were the MP36PH-3S and MP36PH-3C. With the 3S, the power supply for the passenger cars was provided by a static inverter, which made it necessary for the diesel engine to run constantly at nominal speed to provide the required frequency. When calling up the maximum 500 kW, the power available to the traction motors was reduced by this value. The 3C used an additional Caterpillar C27, which provided power for the train independently of the main diesel. From 2015, all Type 3S engines have been upgraded to the same level as the 3C to reduce stationary noise and fuel consumption.

From 2007 the MP40PH-3C was delivered, which got a newer EMD engine of the 710 series, which provided 4,000 hp. Here, too, an additional diesel engine was used to supply the train. From 2013 the MP32PH-Q was manufactured, which resulted from the conversion of existing EMD GP40WH-2 and differs from the other models in that the hoods around the prime mover were unchanged and only the head got a new shape. Despite the 32 in the name, the existing engines were upgraded from 3,000 to 3,600 hp. 

Since the new registration of locomotives with the EMD two-stroke engine was no longer possible with the EPA Tier 4 emissions standard coming into effect in the USA on January 1, 2015, production of the locomotives with these engines ended. Now MPI offered the MP54AC with two 2,700 hp Cummins QSK60, which meet the new emissions standard and have an AC drive system. To reduce fuel consumption and emissions, one of the engines can be switched off as needed, making the MP54AC a genset loco.

The largest number is made up of the MP36PH-3C, of which just over 100 were built. It went to a total of nine commuter companies in the USA. Twenty-seven examples of the similar -3S were built for Metra in the Chicago area. Of the MP40PH-3C, most of the 71 examples went to the Canadian GO Transit, as did all 26 examples of the MP54AC. The first MP54AC was created by converting a GO Transit MP40PH-3C accordingly. Only eleven examples of the MP32PH-Q were built for SunRail in the Orlando, Florida area. Most of these had been converted from former MARC (Maryland Area Rail Commuter) GP40WH-2s.