A fourth generation of diesels took the form of thirty-four locomotives, again from General Motors, which arrived in the early 1990s. This was a joint order by IÉ and NIR, with thirty-two locomotives for the former and two for the latter. They were again supplied by General Motors Electro-Motive Division. IÉ designated their locomotives the GM 201 class; numbered 201 to 234 (the NIR locomotives were later prefixed with an 8). These locomotives are the most powerful diesels to run in Ireland, and are of 3200 horsepower (2.5 MW), which enabled further acceleration of express services. The NIR locomotives, although shipped in NIR livery, were repainted in 'Enterprise' livery, as were six of the IÉ locomotives.