Turbochargers are the most usual means of forced aspiration used
on motor vehicles. They work as follows: a turbine wheel uses
the energy in the exhaust to drive a compressor wheel on the
same shaft, (but in the intake air flow). It compresses the
intake air and forces it into the cylinders. This supplies the
engine with more oxygen for the combustion process. Compared
with a naturally aspirated engine with the same displacement,
the turbocharger increases power and torque as well as
efficiency. Exceptionally high-performance engines in certain
Audi models even have two turbochargers (“biturbo”). In the
past, increased power was the main reason for using a
turbocharger, but today energy conservation and reduced
emissions are the primary reasons, together with good
performance. Many modern diesel engines have turbochargers with
Variable Turbine Geometry (VTG). The angle of the blades changes
according to engine load.