How to control the air intake when idling?

Generally speaking, the control methods of idle intake can be divided into two types: direct throttle and bypass. Throttle direct-acting type is to control the opening of throttle through motor, and then control the air intake at idle speed. The larger the throttle opening, the more air intake, and vice versa. Bypass type is to control the cross-sectional area of bypass through idle motor, and then control the air intake at idle speed. The larger the cross-sectional area of the bypass pipe, the more air intake, and vice versa. The bypass air passage and the throttle control air passage are connected in parallel. When idling, the throttle valve is completely closed, and all the air entering the engine enters through the bypass pipe. Therefore, controlling the cross-sectional area of the bypass pipe can control the air intake.