EMD 645 - History

History

Developed from the earlier 567 series engines, the 645 series engines entered production in 1965. Compared to the 567 series engine's bore of 8-1/2 in (215.9 mm), the 645 series has a larger bore of 9-1/16 in (230.2 mm) while maintaining the same stroke and deck height. It is this same deck height, which facilitates using current 645 service parts in older 567 engines. However, the 567 crankcase is of a different design from the 645 (and the quite similar 710) which somewhat limits parts interchangeability. 567E engines actually employ a 645E block, but are fitted with 567 power assemblies, so the parts interchangeability is somewhat greater with the 567E engines, although these engines are somewhat rare.

Certain 645E and all 645F engines are turbocharged. The turbocharger is a mechanically-assisted turbo-compressor. During engine startup, and at lower power levels, during which there is not sufficient exhaust heat energy to drive the turbine fast enough for the compressor to supply the air necessary for combustion, the engine drives the compressor through a gear train and an overrunning clutch. At higher power levels, during which there is sufficient exhaust heat energy to drive the turbine fast enough for the compressor to supply the air necessary for combustion, the over-running clutch in the gear train is disengaged, and the turbo-compressor becomes a true turbocharger. Turbocharging provides higher horsepower and good running characteristics at all altitudes. Turbocharging also improves fuel consumption and reduces emissions.

The 645 series engine models have a uniform maximum engine speed of 900 revolutions per minute compared to 800-900 rpm of the 567 series. 900 rpm became essential for 60 Hz stationary power generator applications, and certain passenger locomotives equipped with 60 Hz 480-volt three-phase "head-end power" systems for the trailing passenger cars' lighting, air conditioning and cooking requirements. With an 8-pole alternator as an electric generator, 60 Hz power output is the result and the engine's Woodward governor can be set to maintain 900 rpm. In traction applications, the engine speed is, of course, variable.

EMD built an SD40 demonstrator (number 434) in July 1964 to field test the 16-645E3 engine. EMD built another eight SD40 demonstrators (numbers 434A through 434H) and a GP40 demonstrator (number 433A) in 1965. In December 1965 and January 1966 EMD built the first three SD45 demonstrators (numbers 4351 through 4353) to field test the 20-645E3 engine.

When the 645 engine entered production in 1965, it was used in EMD's 40 Series (GP40, SD40 and SD45) in 3,000 horsepower (2,200 kW), sixteen-cylinder form and in 3,600 horsepower (2,700 kW), twenty-cylinder form.

The 40 Series was later expanded to include the so-called 38 Series (GP38, SD38) and the so-called 39 Series (GP39, SD39), but these are lower-powered versions of the basic 40 Series so these models are functionally a part of the 40 Series. All of these share a great many common components and subsystems, thereby significantly reducing cost and increasing interchangeability. The 38 Series became one of EMD's more popular models.

EMD's recent model naming convention usually is by tens (40, 50, 60 and 70, etcetera). When creating a lower-powered model from a basic model, the naming usually goes backwards from the basic model number by ones, such as, for example, 39 (from the 40 Series, with 12, not 16 cylinders) and 38 (Roots-blown, not turbocharged, from the 40 series). Occasionally, when creating a higher-powered model from a basic model, the naming usually goes forwards from the basic model number by fives, such as 45 (from the 40 Series, 3600 HP instead of 3000, with 20, not 16 cylinders) and 75 (from the 70 Series, with 4500, not 4300 HP).

The 710 engines do not offer a Roots-blown model, but nothing in the basic design of this engine prevents such an offering. However, the 710 engines were introduced late enough to be subject to emissions controls, and turbocharging significantly improves emissions compliance.