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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.〔40-series versions of the 645, save the initial teething problems with the 20-645E, which were eventually resolved, proved to be exceptionally reliable.〕 The EMD 710 is a relatively large medium speed two-stroke diesel engine that has displacement per cylinder,〔http://www.emdiesels.com/emdweb/products/pdf/EMD_710ECO_Repower_Solutions.pdf〕 and a maximum engine speed of 900 rpm. 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. Since its introduction, EMD has continually upgraded the 710G diesel engine. Power output has increased from on 1984's 16-710G3A to (as of 2012) on the 16-710G3C-T2, although most current examples are . 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 trouble-free 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. 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 V-8, V-12, V-16, and V-20 configurations, although most current locomotive production is the V-16 engine, whereas most current marine and stationary engine production is the V-20 engine. == Specification == All 710 engines are two-stroke 45 degree V-engines. The 710, and the earlier 645 and 567, are the only two-stroke engines commonly used today in locomotives. The 710 model was introduced in 1985 and has a longer stroke (now ) than the 645 ( bore). The engine is a uniflow design with four poppet-type 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.〔Bernard Challen, Rodica Baranescu (ed.), ''Diesel Engine Reference Book Second Edition'', Butterworth-Heinemann 1999 ISBN 0 7506 2176 1 pg 598〕 Pre-1995 engines have mechanically controlled unit injectors (UIs), patented in 1934 by General Motors, EMD's former owner. Post-1995 engines have electronically controlled unit injectors (EUIs) which fit within the same space as a unit injector.〔The camshaft still operates the unit injector's built-in plunger pump, as the pump's performance is unequaled in atomizing and injecting the fuel at great pressure; the electronics controls the timing of certain events within the unit injector, thereby achieving, variously, maximum horsepower, minimum emissions or minimum fuel consumption, as directed by the engine control system.〕 An EUI is EMD's implementation of EFI on its large-displacement diesel engines. See EMD 645 for general specifications common to all 567, 645, and 710 engines. Unlike the two earlier engines, which could use either a Roots blower or a turbocharger, the 710 engine is offered only with turbocharging. The turbocharger (a combination turbo-compressor system) follows EMD's innovative design that uses a gear train and over-running clutch to drive the compressor rotor during low engine speed, when exhaust gas temperature (and, correspondingly, heat energy) alone is insufficient to drive the turbine. At higher engine speeds, increased exhaust gas temperature is sufficient to drive the turbine and the clutch disengages, turning the turbo-compressor system into a true turbocharger. The turbo-compressor can revert to compressor mode momentarily during demands for large increases in engine output power. While more expensive to maintain than Roots blowers, the turbocharger significantly reduces fuel consumption and emissions, while improving high-altitude performance. Additionally, EMD's turbo-compressor can provide 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 offered both Roots blown and turbocharging, EMD's turbo-compressor is an integral part of all 710 models, therefore this 50 percent increase is already incorporated into the maximum rated power of all 710 models. The putative horsepower of an otherwise equivalent, but Roots blown (i.e., "naturally aspirated") 710, may be approximated by multiplying the turbocharged horsepower by 0.67. Horsepower for naturally aspirated engines (including Roots-blown two-stroke engines) is usually derated 2.5 percent per above mean sea level, a tremendous penalty at the 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. Certain models have engine controls that permit lower fuel consumption (possibly at the expense of higher emissions) or lower emissions (possibly at the expense of higher fuel consumption). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「EMD 710」の詳細全文を読む スポンサード リンク
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