The PCM energizes the VSC solenoid valve during low engine speed and vacuum is applied to the VSC shutter valve actuator to close the VSC shutter valve. When the VSC shutter valve closes, the intake air passage becomes narrower than normal due to the closing of one of the two intake air ports, which increases the intake airflow speed and create a strong lateral airflow in the combustion chamber.
During low engine speeds, the strong lateral airflow in the cylinder disperses vaporized fuel injected from the fuel injector nozzle and mixes it with the air uniformly.
