Turbocharger operation
The exhaust gases, which are still quite hot, are fed to the turbine wheel, causing the wheel to rotate. When the turbine rotates, the gases expand and transmit excess power to the unit shaft, which is spent on compressing the air in the compressor, located on a common shaft with the turbine. The rotation frequency of the turbocharger shaft varies in the range of 20,000-115,000 rpm, which is accompanied by a characteristic "whistle" of the turbine.
Gas bypass valve past the turbine
(The original source is located on the website: «ToyotaMAN»)
If the pressure of the air supplied by the compressor exceeds the permissible value (according to engine reliability conditions), the exhaust gases are bypassed by the turbine by a special valve with an independent drive. The drive is a diaphragm driven by the boost air pressure. This is how the boost pressure is regulated with feedback.