Turbocharger 

Forced air induction system   

 Turbocharger known as a turbo, Magna charger, or supercharger is a turbine-driven forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra compressed air into the combustion chamber  

Turbocharger 

A turbo uses the heated exhaust to power a turbine wheel, by doing this the turbo does not directly reduce power.    

The turbo consists of two chambers connected with a center housing. The chambers contain a turbine wheel and an impeller wheel connected by a shaft which passes through the center housing. 

The turbo is position as close as possible to the exhaust manifold. As exhaust gas enters the turbocharger, it rotates the turbine blades.    

 The turbine wheel and compressor wheel are on the same shaft so that they turn at the same speed.

The rotation of the compressor wheel draws air in through a central inlet and centrifugal force pumps it through an outlet at the edge of the housing. 

There are a set of bearings that support a shaft and is lubricated by the engine oil.    

Turbocharger 
wastegate

A wastegates job is to control boost pressure.   

To prevent over boost and severe engine damage, most turbocharger system uses a wastegate. A wastegate is a valve similar to a door that can open and close.   

It is a bypass valve at the exhaust inlet to the turbine, which allows all of the exhaust into the turbine, or it can route part of the exhaust past the turbine to the exhaust system.   

If the valve is closed, all of the exhaust travels to the turbocharger. When a predetermined amount of boost pressure develops in the intake manifold, the wastegate valve is open.  

As the valve opens, most of the exhaust flow directly out the exhaust system, bypassing the turbocharger.   

When less exhaust flowing across the vanes of the turbocharger, the turbocharger decreases in speed and boost pressure is reduced.  

When the boost pressure drops, the wastegate valve closes to direct the exhaust over the turbocharger vanes to again allow the boost pressure to rise.   

The wastegate operation is a continuous process to control boost pressure.   

The wastegate is the pressure control valve of a turbocharger system. 

Some of today's cars the wastegate is usually controlled by the Powertrain Controlled Module (PCM) through a boost control solenoid.