In a twin-screw supercharger, the male rotor (left) turns clockwise, while the female rotor (right) turns counterclockwise. The screw-shaped rotors compress the incoming air between them as the air traverses the length of the rotors. The air then takes a direct path downward into the intake manifold. In contrast, in a Roots-style blower the left-side lobe turns counterclockwise while the right-side rotor turns clockwise. The intake air is pushed against the sides of the supercharger case before discharging into the intake manifold. Since the air is forced to traverse a longer route, absorbing heat from the supercharger case along the way, the result is higher inlet air temps and lower efficiency.