VTG boost pressure regulation
Exhaust gas turbocharger (TCs) from Bosch Mahle Turbo Systems deliver a high engine torque even at low engine speeds and with a small exhaust gas mass flow (low-end torque). Boost pressure is regulated to prevent the TC from overcharging the engine at higher engine speeds.
TCs from Bosch Mahle Turbo Systems also provide the option of "overboost." This refers to a temporary excessive increase in the boost pressure, e.g., when accelerating (⇒ kickdown).
The variable turbine geometry mechanism regulates the boost pressure independently of the engine speed via the adjustable guide vanes. In order to provide a high boost pressure at low rotational speeds, the guide vanes are positioned on a narrow inlet cross section. This results in the exhaust flow moving at a high speed. The increased kinetic energy of the exhaust gas is transferred to the turbine, raising the rotational speed. At high engine speeds, the guide vanes free up a large inlet cross section and the exhaust flow impacts the interior of the turbine blades at a lower speed.
The VTG has been specifically developed by Bosch Mahle Turbo Systems to achieve a very high level of turbine efficiency. The portfolio comprises various VTG sizes for passenger car diesel engines up to an engine output of 165 kW.
