431

range from a low of 900 for an eight cylinder model to as high as 4200 for a twenty cylinder model. Representative rail performance information for locomotives powered by 645 model engines is given in Table 1.(2)

Since its introduction, the 645 engine has been modified in order to improve efficiency. These improvements have been primarily in the areas of:

o Combustion

-increased compression ratio frtm 14.5 to 16.1 inproved fuel injection equipment -relocated the "fire ring" to reduce the size of the combustion chamber envelope o Scavenging/breathing -increased turbocharger efficiency -modified exhaust valve timing -"fire ring" relocation intake port timing

The cumulative effects of these modifications on the efficiency of the 16-cylinder 645F3B engine as compared to the 645F3 engine has resulted in a 6.1 percent reduction in brake specific fuel consumption (BSFC). Table II contains additional information regarding the specifications and performance of the 16 cylinder 645 engines used as prime movers in diesel-electric locomotives.

Model 710 Diesel Engine The Model 710 diesel engine is the replacement

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