Wastegate

A wastegate is a valve that controls the flow of exhaust gases to the turbine wheel in a turbocharged engine system.

External wastegates can be much larger since there is no constraint of integrating the valve or spring into the turbocharger and turbine housing.

This can be achieved through a specially designed bracket that easily bolts on and restricts the movement of the actuator arm, keeping it from opening.

Disadvantages in comparison to an external wastegate include a limited ability to bleed off exhaust pressure due to the relatively small diameter of the internal bypass valve, and less efficient performance under boost conditions.

A "divorced" wastegate dumps the gases directly into the atmosphere, instead of returning them with the rest of an engine's exhaust.

A small hose can connect from the turbocharger compressor outlet, charge pipes, or intake manifold to the nipple on the wastegate actuator.

Air pressure allowed to enter this second port aids the spring to push harder in the direction of closing the wastegate.

Beginning in the 2011 model year the 2.0-liter Theta II turbocharged gasoline direct-injection (GDI) engine introduced in the Hyundai Sonata includes a PCM operated electronic servo wastegate actuator.

The wastegate is also held open during cold starting to lower emissions by speeding up initial catalyst light-off.

Starting in November 2015,[7] Honda Earth Dreams direct injected turbocharged engines with 1.5 litre displacement employ an ECU driven electric wastegate.

As the aircraft climbs and the air density drops, the density controller slowly closes the valve and traps more oil in the wastegate actuator, closing the wastegate to increase the speed of the turbocharger and maintain rated power.

This maintains an optimum balance between a low turbocharger workload and a quick spool-up time, and also prevents surging caused by a bootstrapping effect.