The resonance intake system increases the intake volume by exploiting the fact that air oscillates as it passes through the intake manifold. The system can adjust to engine speed. Benefits of this include higher torque at low engine speeds and a flatter torque curve. The 911 Carrera S models operate a two-stage system.
The entire intake system is made from lightweight plastic. In the 911 Carrera models, the resonator volume of the air filter housing varies with engine speed to bring added character to the engine sound, which becomes much more powerful at higher rpm.