Automobile flow sensors are critical in ensuring the engine air-fuel ratio, improving fuel efficiency, and reducing pollution. This paper presents a self-powered shaftless turbine intake flow sensor (STIFS) for automobiles consisting of a ball-bearing triboelectric nanogenerator (BB-TENG) and a magnetic field modulation type magnetic gear electromagnetic generator (MG-EMG). The contact electrification between the rolling ball and the outer ring of the BB-TENG generates a periodic electrical signal for flow sensing. In particular, the magnetic gear can improve the BB-TENG signal frequency and MG-EMG output performance. The smoothness of the airflow is improved by designing the shaftless turbine using the computational fluid dynamics (CFD) method, and the start flow of the STIFS is 160 L/min. The sensing sensitivity of the STIFS reaches 0.71 Hz/L·min−1·in the monitoring range of 300–900 L/min, and there is a well linear relationship between frequency and flow rate. In addition, the MG-EMG can generate output voltages and currents of 374 V and 31 mA to power data analysis and transmission modules in real-time. This work presents a novel methodology for self-powered wireless airflow sensing in large-flow pipelines, such as automobile intake pipes.