The compact-sized module for the new two-stage turbocharging concept consists of a small high-pressure (HP) plus a large low-pressure (LP) turbocharger. Both comprise a turbine and a turbine-driven compressor, and are connected with one another in series:

• The HP turbine has a diameter of 38.5 mm and is positioned directly in the exhaust manifold. The flow of exhaust gases flows through this turbine first, causing it to rotate at speeds of up to 248,000 revolutions per minute.
• Integrated into the HP turbine housing is a bypass duct, which can be opened or closed by means of a charge-pressure control flap triggered by an actuator. If the duct is closed, the entire exhaust, the whole exhaust stream flows through the HP turbine, meaning that all of the energy contained in the exhaust gases can be directed towards propelling the HP turbine only. In this way, the optimum charge pressure can be built up at low rev speeds.
• As the engine speed increases, the charge-pressure control flap opens to prevent the HP charger from becoming overloaded. A portion of the exhaust stream now flows through the bypass duct to relieve the load on the high-pressure stage.
• Downstream from the HP turbine, the two exhaust gas streams join up again, and any remaining exhaust energy drives the 50-millimetre LP turbine at a maximal speed of 185,000 revolutions per minute.
• To protect it against overload, the LP turbine also features a bypass duct, which is opened and closed by means of an actuator-controlled flap known as the "wastegate".
• Once the engine reaches medium rev speeds, the HP turbine's charge-pressure control flap is opened so wide that the HP turbine ceases to perform any appreciable work. This allows the full exhaust energy to be directed with low losses into the LP turbine, which then does all of the turbine work.