Method and system for a boosted engine

The invention relates to a method and a system for a boosted engine. Methods and systems are provided for coordinated control of a compound boosting system, including a first compressor staged upstream of a second compressor in an engine intake. In one example, a method may include operating the second, downstream compressor in steady-state to achieve an overall pressure ratio across the compoundboosting system while operating the first, upstream compressor transiently, based on an airflow shortfall at the downstream compressor. A timing and amount of electric assistance provided to transiently operate the first, upstream compressor may be adjusted dynamically as the pressure ratio across the second compressor changes. 本发明涉及用于升压发动机的方法和系统。提供用于复合升压系统的协调控制的方法和系统，该复合升压系统包括在发动机进气装置中的第二压缩机的上游分级的第压缩机。在个示例中，方法包括：基于下游压缩机处的空气流不足，在稳态下操作第二下游压缩机以实现复合升压系统两端的总压力比，同时瞬时地操作第上游压缩机。当第二压缩机两端的压力比改变时，动态地调节为瞬时操作第上游压缩机而提供的电动协助的正时和量。