EMD 12 cylinder 645E3 turbocharged engine.

(Karsini, Public domain, via Wikimedia Commons)



The EMD 645 is a family of diesel engines that was designed and manufactured by the Electro-Motive Division of General Motors. While the 645 series was intended primarily for locomotive, marine and stationary engine use, one 16-cylinder version powered the 33-19 "Titan" prototype haul truck designed by GM's Terex division

The 645 series was an evolution of the earlier 567 series and a precursor to the later 710 series. First introduced in 1965, the EMD 645 series remained in production on a by-request basis long after it was replaced by the 710, and most 645 service parts are still in production. The EMD 645 engine series is currently supported by Electro-Motive Diesel, Inc., which purchased the assets of the Electro-Motive Division from General Motors in 2005.

In 1951, E. W. Kettering wrote a paper for the ASME entitled, History and Development of the 567 Series General Motors Locomotive Engine, which goes into great detail about the technical obstacles that were encountered during the development of the 567 engine. These same considerations apply to the 645 and 710, as these engines were a logical extension of the 567C, by applying a cylinder bore increase, 645, and a cylinder bore increase and a stroke increase, 710, to achieve a greater power output, without changing the external size of the engines, or their weight, thereby achieving significant improvements in horsepower per unit volume and horsepower per unit weight.

Due to emissions restrictions these engines have been gradually phased out for the 4 stroke alternatives.



The 645 series engines entered production in 1965. As the 567 series had reached its limits in horsepower increases, a larger displacement was needed; this was accomplished by increasing the bore from 8+1⁄2 in (216 mm) on the 567 series to 9+1⁄16 in (230 mm) on the 645 series, while maintaining the same stroke and deck height. While the crankcase was modified from the 567 series, 567C and later engines (or 567 engines which have been modified to 567C specifications, sometimes referred to as 567AC or 567BC engines) can accept 645 series service parts, such as power assemblies. Conversely, the 567E engine employs a 645E series block with 567 series power assemblies.

All 645 engines utilize either a Roots blower or a turbocharger for cylinder scavenging. For turbocharged engines, the turbocharger is gear-driven and has a centrifugal clutch that allows it to act as a centrifugal blower at low engine speeds (when exhaust gas flow and temperature alone are insufficient to drive the turbine) and a purely exhaust-driven turbocharger at higher speeds. The turbocharger can revert to acting as a supercharger during demands for large increases in engine output power. While more expensive to maintain than Roots blowers, EMD claims that this design allows "significantly" reduced fuel consumption and emissions, improved high-altitude performance, and even up to a 50 percent increase in maximum rated horsepower over Roots-blown engines for the same engine displacement.

Horsepower for naturally aspirated engines (including Roots-blown two-stroke engines) is usually derated 2.5 percent per 1,000 feet (300 m) above mean sea level, a tremendous penalty at the 10,000 feet (3,000 m) or greater elevations which several Western U.S. and Canada railroads operate, and this can amount to a 25 percent power loss. Turbocharging effectively eliminates this derating.

The 645 series has a maximum engine speed of between 900 and 950 revolutions per minute (rpm), an increase over the 800 to 900 rpm maximum speed for the 567 series. An engine speed of 900 rpm was essential for 60 Hz stationary power generator applications and certain passenger locomotives equipped with 60 Hz, 480-volt three-phase "head-end power" systems. When used solely for traction purposes, the engine speed varies depending on the throttle position. The 950 rpm maximum speed of the 645F engine proved to be too high, thereby compromising its reliability, and the replacement engine, the 710G, reverted to 900 rpm maximum speed.

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

When the 645 engine entered production in 1965, a large series of new locomotive models was introduced. The turbocharged version 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. EMD also introduced the Roots-blown 38 Series (GP38, SD38) and turbocharged, twelve-cylinder 39 Series (GP39, SD39). All of these locomotive models extensively share common components and subsystems, thereby significantly reducing cost and increasing interchangeability. The GP38-2 and SD40-2 became the most popular models of the series and among the most popular locomotive models ever built.

Starting with the introduction of the 645 series engines, EMD's model naming convention generally increased model designs by ten (such as with the 40, 50, 60 and 70 series). The number was reduced by one for twelve-cylinder versions (such as the 39, 49 and 59 series); reduced by two for Roots-blown versions (for the 38 series); and increased by five for higher-horsepower versions (such as the 45 and 75 series).


 EMD 16-645, animated GIF to show cylinder firing order.

8-, 12-, and 20-645 have similar arrangements, with the right bank being numbered sequentially before the left bank,

so a 20-645 would have cylinders No. 1–10 in the right bank and No. 11–20 in the left bank.

The front of the engine is at the rear of the locomotive; the rear of the engine is at the front of the locomotive.

(Mliu92, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons)


Specifications (many are common to 567 and 710 engines)

All 645 engines are two-stroke 45-degree V-engines. Each cylinder is of 645 cubic inches (10.57 L) displacement, hence the name; with a bore of 9+1⁄16 inches (230 mm), a stroke of 10 inches (254 mm) and a compression ratio of 14.5:1. The engine is a uniflow design with four poppet-type exhaust valves in the cylinder head and charge air scavenging ports within the sides of the cylinders. All engines use a single overhead camshaft per bank, with exhaust valves operated by two cam lobes (each of which operates two exhaust valves through a "bridge") and one cam lobe to operate the Unit injector which is in the center of the four exhaust valves. Rocker arms are roller-equipped to reduce friction while hydraulic valve actuators are used to reduce valve lash. Post-1995 710 engines employ Electronic Unit injectors, however these injectors still utilize a camshaft-actuated piston pump, as on non-EFI injectors.

Cylinders in each V-pair are directly opposite each other, and the connecting rods are of a fork-and-blade arrangement, with "fork" rods on one bank of cylinders and "blade" rods on the other (with the same stroke on both banks). (In contrast, General Electric's 7FDL and 7FDM engines use "articulated" master-and-slave connecting rods, essentially two adjacent cylinders on a radial engine, and have a slightly longer stroke on the bank using slave rods.) The engines are provided with either a single or twin Roots blower, or a single mechanically-assisted turbocharger, depending on required power output.

For maintenance, a power assembly, consisting of a cylinder head, cylinder liner, piston, piston carrier and piston rod can be individually replaced relatively easily and quickly. The engine block is made from flat, formed and rolled structural steel members and steel forgings welded into a single structure (a "weldment"), so it can easily be repaired using conventional shop tools.

  • Orientation: The "front" of the engine (the engine governor and fluid pump end) is actually at the rear end of the locomotive, immediately adjacent to the locomotive's coolant supply and cooling system; the "rear" of the engine (the induction system and traction generator or alternator end) is at the front end of the locomotive, immediately adjacent to the locomotive's electrical cabinet.
  • Rotation: Engine rotation is in the conventional clockwise direction, as viewed from the "front" of the engine, but is in a counterclockwise direction, as viewed from the front of the locomotive. Marine and stationary installations are available with either a left or a right-hand rotating engine.
  • Firing order
      • Eight cylinder: 1, 5, 3, 7, 4, 8, 2, 6
      • Twelve cylinder: 1, 7, 4, 10, 2, 8, 6, 12, 3, 9, 5, 11
      • Sixteen cylinder: 1, 8, 9, 16, 3, 6, 11, 14, 4, 5, 12, 13, 2, 7, 10, 15
      • Twenty cylinder: 1, 19, 8, 11, 5, 18, 7, 15, 2, 17, 10, 12, 3, 20, 6, 13, 4, 16, 9, 14
  • Exhaust valves: Four per cylinder
  • Main bearings

       • Eight cylinder: 5 (one-piece crankshaft)
       • Twelve cylinder: 7 (one-piece crankshaft)
        Sixteen cylinder: 10 (two-piece crankshaft, pinned and bolted in the middle)
       • Twenty cylinder: 12 (two-piece crankshaft, pinned and bolted in the middle)

  • Fuel injection: Unit injector; Electronic unit injector in post-1995 engines
  • Engine starting

 • AC traction generator: Dual electric starting motors, parallel-connected 64 volt starters in early applications, series-connected 32 volt starters in late applications
 • DC traction generator: Generator series field
 • AC power generator: Dual pneumatic starters in most stationary engine applications

  • Engine Control

 • Woodward PGE locomotive governor, or equivalent, in mechanical engines; EMD engine control unit in electronic engines

  • Weight (E3B turbocharged models)
     • Eight cylinder: 22,050 pounds (11.025 tons)
     • Twelve cylinder: 28,306 pounds (14.153 tons)
     • Sixteen cylinder: 36,425 pounds (18.2125 tons)
     • Twenty cylinder: 43,091 pounds (21.5455 tons)



ID Cylinders Induction Rated RPM Power HP Power MW Year Introduced Applications
8-645C 8 Blower (1) 900 1100 0.8 G18AR, New Zealand DBR class
6-645E 6 Blower (1) 900 750 0.6 1967 Victorian Railways Y class (G6B)
8-645E 8 Blower (1) 900 1000 0.75 1966 SW1000, SW1001, V/Line P class, Victorian Railways T class (3rd series) / H class, CIE 201 Class (rebuilt), Renfe Class 310
12-645E 12 Blower (2) 900 1500 1.1 1966 MP15DC, MP15AC, G22, SW1500, SW1504, GP15-1, GP15AC, CIE 001 Class (rebuilt), Commonwealth Railways NJ class, MV Liberty Star, SJ Class T44
16-645E 16 Blower (2) 900 2000 1.5 1966 GP38, GP38-2, SD38, SDP38, SD38-2, NSWGR 422 Class, Victorian Railways X class (2nd & 3rd series), G26, Renfe Class 319
8-645E3 8 Turbocharger 900 1650 1.2 MP15T, FGC 254 Series
12-645C 12 Blower (2) 900 1650 1.2 G22AR, New Zealand DC class
12-645E3 12 Turbocharger 900 2300 1.7 1968 GP39, GP39-2, SD39, SDL39, CIE 071, GT22, British Rail Class 57/0 & 57601
16-645E3 16 Turbocharger 900 3000 2.2 1965 GP40, GP40-2, GP40P, GP40P-2, GP40TC, SD40, SD40A, SD40-2, SD40T-2, SDP40, SDP40F, F40PH, Commonwealth Railways CL class (Original), Australian National AL class (Original), WAGR L class, VR C Class, GT26CW, DSB Class MZ (series I–II)
20-645E3 20 Turbocharger 900 3600 2.7 1965 SD45, SD45-2, SDP45, F45, FP45, DDM45, DSB Class MZ (series III–IV)
16-645E3A 16 Turbocharger 950 3300 2.5 1969 DDA40X (dual engine), Renfe Class 333
20-645E3A 20 Turbocharger 950 4200 3.1 1970 SD45X
8-645E3B 8 Turbocharger 904 1514-1666 1.1-1.2 Proposed
12-645E3B 12 Turbocharger 904 2380-2570 1.8-1.9 JT22CW, V/Line A class, V/Line N class (2nd series)
16-645E3B 16 Turbocharger 904 3195-3390 2.4-2.5 F40C, New South Wales 81 class locomotive, Australian National BL class, V/Line G class (original), NSB Di 4, DSB Class ME, M62M Rail Polska
20-645E3B 20 Turbocharger 904 3765-3960 2.8-3.0 SD45T-2
8-645E3C 8 Turbocharger 904 1500 1.1 GP15T
12-645E3C 12 Turbocharger 900 2510 1.8 V/Line N class (1st series), New Zealand DFT class, Queensland Railways 2300 class
16-645E3C 16 Turbocharger 950 3300 2.5 British Rail Class 59, V/Line G class (original), Pacific National XRB class, Freight Australia XR class, VL class (Australia), Commonwealth Railways CL class (rebuilt versions), Australian National ALF class, TCDD DE33000, F40PH-2, SD40E, Henschel DE3300
16-645E4 16 Turbocharger 900 3300 2.46 1973 Terex 33-19 "Titan" haul truck
16-645F 16 Turbocharger 950 3500 2.6 1977 GP40X, GP50, SD40X, SD50
12-645F3B 12 Turbocharger 950 2800 2.1 GP49, British Rail Class 57/3 & 57602-57605
16-645F3B 16 Turbocharger 950 3600 2.7 EMD FT36HCW-2-Korail 7000 Series; MPI MPXpress MP36PH-3S and -3C, RL class, V/Line G class (rebuilt)