A car engine air-intake unit has a round main body. The main body has airflow guides and airflow guiding plates to guide air flowing into the intake tube to rotate, and blades are provided which protrude out of the main body and extend from the airflow guiding plates to increase the rotating angle and stroke of the guided air flow. The intake unit can be used in cooperation with any of various specific air-intake tubes, and can be assembled and adjusted to support different air intake amounts and any of various air-intake tubes of different bores, and thus offers convenience of use.