The compressor housing is where clean air is gathered and compressed before being forced into the engine - it houses the compressor wheel. A compressor housing includes a compressor inlet duct and an inlet for a compressor wheel. The compressor housing includes at least one appendix positioned between an upstream portion of the compressor inlet duct and the compressor wheel inlet. On modern turbochargers, this is usually manufactured from aluminium, and typically features a ‘volute’ or spiral shaped design, which helps to provide optimum airflow and air pressure to the engine.