Method and system for a boosted engine

A method for a boosted engine, comprising:

• during selected low load conditions when an electrically-driven compressor coupled to a turbine-driven compressor is not activated, commanding a bypass valve closed to direct intake air to an engine via the deactivated electrically-driven compressor, and further comprising:
• monitoring a speed of the electrically-driven compressor during the directing of intake air to the engine via the deactivated electrically-driven compressor;
• and
• indicating that the bypass valve is stuck at least partially open responsive to the monitored speed being lower than a threshold speed after commanding the bypass valve closed.

A vehicle system, comprising:

• an engine;
• a branched intake passage system including a common upstream intake passage branching into first and second parallel branches, and rejoining into a common downstream intake passage;
• a twin turbocharger including a first intake compressor in the first branch, driven by a first exhaust turbine, and a second intake compressor in the second branch, driven by a second exhaust turbine;
• a twin supercharger including a third intake compressor driven by a first electric motor, the third intake compressor housed in a first bypass passage bypassing the common downstream intake passage, and a fourth intake compressor driven by a second electric motor, the fourth intake compressor housed in a second bypass passage bypassing the common downstream intake passage, the first bypass passage and the second bypass passage parallel to each other and to the common downstream passage;
• a bypass valve coupled in the common downstream passage, downstream of an inlet of each of the first and second bypass passages;
• and
• a controller with computer readable instructions stored on non-transitory memory for:
• while operating the engine with each of the first, second, third, and fourth intake compressors deactivated, selectively closing the bypass valve to direct all intake air to the engine via a combination of the first and second branches, and then via a combination of the first and second bypass passages, while bypassing the common downstream passage, the selectively closing based on engine fuel economy with the bypass valve closed relative to bypass valve open;
• and
• responsive to an increase in torque demand, maintaining the bypass valve closed while activating the third and fourth intake compressors.