The ALCO PB1 2000Hp. built from 1946 to 1949, gear ratio gave speeds of 80mph, 90mph, 100mph, and 117mph. used for passenger trains, later freight. The engine had an exhaust-actuated turbocharger so that until the engine revved up to speed there was a lack of oxygen causing improper combustion and a lot of black smoke.
This is SP .In 1948-1949 SP got 6 PB1s and in 1950-1953 7 PB2s, note B units had no numbers on the side.