An EMD 12-710G3B engine, installed in an Iarnród Éireann 201 class locomotive.

(Karsini, Public domain, via Wikimedia Commons)


Progress Rail logo.


The EMD 710 is a line of diesel engines built by Electro-Motive Diesel (previously General Motors' Electro-Motive Division). The 710 series replaced the earlier EMD 645 series when the 645F series proved to be unreliable in the early 1980s 50-series locomotives which featured a maximum engine speed of 950 rpm. The EMD 710 is a relatively large medium-speed two-stroke diesel engine that has 710 cubic inches (11.6 liters) displacement per cylinder, and a maximum engine speed of 900 rpm.

In 1951, E. W. Kettering (son of Charles F. 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 development of the 567C, applying a cylinder bore increase (645) and a stroke increase (710), to achieve a greater power output, without changing the external size or weight of the engines, thereby achieving significant improvements in horsepower per unit volume and horsepower per unit weight.

Since its introduction, EMD has continually upgraded the 710G diesel engine. Power output has increased from 3,800 horsepower (2,800 kW) on 1984's 16-710G3A to 4,500 horsepower (3,400 kW) (as of 2012) on the 16-710G3C-T2, although most current examples are 4,300 horsepower (3,200 kW).

The 710 has proved to be exceptionally reliable, but the earlier 645 is still supported and most 645 service parts are still in new production, as many 645E-powered GP40-2 and SD40-2 locomotives are still operating after four decades of service, and these often serve as a benchmark for engine reliability, which the 710 would meet and eventually exceed, and quite a number of non-SD40-2 locomotives (SD40, SD45, SD40T-2, and SD45T-2, for example, and even some SD50s), have been rebuilt to the equivalent of SD40-2s with new or remanufactured engines and other subsystems, using salvaged locomotives as a starting point. Some of these rebuilds have been made using new 12-cylinder 710 engines in place of the original 16-cylinder 645 engines, retaining the nominal rating of 3000 horsepower, but with lower fuel consumption.

Over the production span of certain locomotive models, upgraded engine models have been fitted when these became available. For example, an early 1994-built SD70MAC had a 16-710G3B, whereas a later 2003-built SD70MAC would have a 16-710G3C-T1.

The engine is made in V8, V12, V16, and V20 configurations, although most current locomotive production is the V16 engine, whereas most current marine and stationary engine production is the V20 engine.



All 710 engines are two-stroke 45° V engines. The 710 model was introduced in 1985 and has a 1-inch (25 mm) longer stroke (now 11 in or 279 mm) than the 645 (10 in or 254 mm stroke). The engine is uniflow scavenged with four poppet exhaust valves in the cylinder head. For maintenance, a power assembly, consisting of a cylinder head, cylinder liner, piston, piston carrier, and piston rod can be individually and relatively easily and quickly replaced. The block is made from flat, formed, and rolled structural steel members and steel forgings welded into a single structure (a "weldment"). Blocks may, therefore, be easily repaired, if required, using conventional shop tools. Each bank of cylinders has a camshaft which operates the exhaust valves and the unit injectors.

Pre-1995 engines have mechanically controlled unit injectors (UIs), patented in 1934 by General Motors, EMD's former owner. Post-1995 engines have electronic unit injectors (EUIs) which fit within the same space as a mechanical unit injector. The use of EUI is EMD's implementation of non-common-rail electronic fuel injection on its large-displacement diesel engines.

See EMD 645 for general specifications common to all 567, 645, and 710 engines.

Unlike the 567 or 645, which could use either Roots blowers or a turbocharger, the 710 engine is only offered with turbocharging. 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. But, unlike the earlier 645 and 567, which could use either turbochargers or Roots blowers, EMD's clutched turbocharger is an integral part of most 710 models.

Horsepower for any naturally aspirated engine is usually derated at 2.5% per 1,000 feet (300 m) above mean sea level, a penalty which becomes extremely large at altitudes of 10,000 feet (3,000 m) or greater as power losses would exceed 25%. Forced induction effectively eliminates this derating.

Some 710 engines have been converted to, or even delivered as, Roots-blown engines with conventional exhaust-driven turbochargers. Others have received modifications that permit lower fuel consumption (but possibly at the expense of higher NOx emissions or reduced power output), lower emissions, or even higher power (at the expense of increased fuel consumption).


Rail versions

ID Type Max RPM Rated HP Power MW Introduced Price
8-710G3A-T2 V8 900 2150 1.6 2007 GT38ACe, GT38LC, GT38ACL, Romanian Class 63, Class 65, Class 66-2, EGM-621, GP22ECO, SD22ECO
8-710G3A-T3 V8 900 2150 1.6 2007 GP20ECO, SD20ECO
8-710G3B-T2 V8 900 2200 1.6 NA JT38CW-DC
12-710G3A V12 900 3000 2.2 1985 GP59, F59PH, Australian National DL class, New South Wales 82 Class.
12-710G3B-T2 V12 900 3150 2.3 2007 SD32ECO EFI equipped.
12-710G3C-EC V12 950 3200 2.3 1993 F59PHI EFI equipped.
12-710G3C-U2 V12 950 3150 2.3 2006 Euro 3000 AC EFI equipped.
12N-710G3B-EC V12 900 3200 2.5 1998 British Rail Class 66, British Rail Class 67, British Rail Class 69, Irish Rail 201 Class, RENFE Class 334, EMD DE/DM30AC
12N-710G3B-EES V12 900 3300 2.5 NA GT42AC, GT42ACL
12N-710G3B-ES V12 900 3200 2.4 1998 WAGR S class (diesel), Downer EDI Rail GT42CU AC, Downer EDI Rail GT42CU ACe, Downer EDI Rail JT42C-DC
16-710G3A V16 900 3800 2.8 1984 GP60, GP60M, GP60B, SD60, SD60M, SD60I, SD60F, Australian National AN Class, New South Wales 90 Class.
16-710G3B V16 900 4000 3.0 1992 Early SD70, SD70M, SD70MAC and SD70I.
16-710G3B-EC V16 900 4000 3.0 1997 SD70, SD70M, SD70M and SD70I models equipped with electronic fuel injection (EFI)|GT46MAC and GT46PAC (Indian Rail Class WDG-4 and WDP-4)
16-710G3B-ES V16 900 4000 3.1 1997 Downer EDI Rail GT46C
16-710G3B-T1 V16 900 4000-4200 3.0-3.1 2003 EPA Tier 1 Emissions compliant/EFI Equipped SD70M, SD70MAC, Alstom PL42AC EPA Tier I emissions compliant/EFI equipped.
16-710G3B-T2 V16 900 4000 3.0 2005 SD70M-2 (Norfolk Southern), MP40PH-3C EPA Tier II emissions compliant/EFI equipped.
16-710G3C V16 950 4300 3.2 1995 SD75M, SD75I.
16-710G3C-EC V16 950 4300 3.2 1995 SD75M, SD75I, EMD SD70 SD90/43MAC EFI equipped.
16-710G3C-ES V16 950 4300 3.2 2007 Downer EDI Rail GT46C ACe
16-710G3C-T1 V16 950 4300 3.2 2003 SD70M (late model), SD70MAC (late model)
16-710G3C-T2 V16 950 4300-4500 3.2 2004 SD70ACe, SD70M-2, SD70ACS, SD70ACe/45South Africa Prasa Afro 4000, EPA Tier II emissions compliant/EFI equipped.
16-710G3C-U2 V16 950 4300 3.2 2006 Euro 4000 EFI equipped.
16N-710G3B-EC V16 950 4500 3.4 2008 GT46PACe and JT46PACe (WDP-4B and WDP-4D), GT46ACe and JT46ACe (WDG-4 and WDG-4D), SD70ACu
20-710G3B-ES V20 900 5000 3.7 1995 SD80MAC EFI equipped,
20-710G3C-ES V20 950 5300 3.9 2011 SD80ACe EPA Tier 1 Emissions compliant.
20N-710G3B-ES V20 900 5500 4.1 2011 EMD GT50AC (Indian locomotive class WDG-5) EFI equipped, SD80ACu (Proposed SD80MAC Rebuild Programme, Now Cancelled)

EMD E23G Overview

Manufacturer: Progress Rail
Configuration: V8, V12, V16, and V20
Displacement: 710 cubic inches (11,600 cm3) per cylinder
Cylinder bore: 9+1⁄16 in (230 mm)
Piston stroke: 11 in (280 mm)
Cylinder block material: Flat, formed and rolled structural steel members, and steel forgings, integrated into a weldment
Cylinder head material: Cast iron, one per cylinder
Valvetrain: 4 Valves per cylinder
Compression ratio: 16:1
RPM range: Idle speed 315; Maximum engine speed: 904
Supercharger: Centrifugal
Turbocharger: Hybrid turbocharger, below half throttle, clutch-driven blower takes over
Management: Electronic
Fuel type: Natural gas
Oil system: Wet sump
Cooling system: Liquid cooling
Power output: 259 hp (193 kw) per cylinder
Dry weight: up to 28.49 tons (25.85 tonnes), (25.44 long tons) 
Predecessor: none, this variant is a conversion
Successor: Caterpillar CG170


See Also:

EMD 567

EMD 645