| 摘要 |
A novel injection-pump plunger used in a unit injector for an EMD-type diesel engine has its upper (cut-off) control edge shaped to retard start of injection at full power from what it is with standard plungers, and to provide in a straight-line manner a relatively small increase in retardation from full load to idle. In a preferred form, the plunger has one or more steps in its upper (cut-off) control edge, the step or steps being formed between adjacent segments of the edge that are associated with different load points. A method of improving emissions/fuel-economy of EMD diesel engines comprises using prototype injection-pump plungers shaped within certain parameters, assessing their performance, selecting new patterns of timing based on the assessment, making new prototype plungers and assessing them, and repeating the steps of selecting, making and assessing if and as required until an assessment indicates compliance with applicable performance standards.
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