CP Rail replaced a 3000 h.p. 16 cylinder freight locomotive engine with a recently designed Caterpillar 3608, 8 cylinder diesel engine of 3100 horsepower. The locomotive was originally manufactured in 1970 by MLW. The re-engined locomotive began operation in August 1988. The expected major benefits of this installation include greatly improved fuel efficiency, reduced maintenance costs and increased productivity.In addition to modern engine design, this installation incorporates microprocessor engine control technology in the form of Caterpillar's Programmable Electronic Engine Controller (PEEC). The PEEC also serves to control alternator excitation and dynamic braking as well as to protect electrical components from excessive electrical loads.This paper describes the features of this installation and the results of testing before and after introduction into freight service.