The wastegate actuator is a valve that diverts exhaust gases away from the turbine wheel helping to control the speed of the turbine and prevent it from over speeding, and in turn, regulating the speed of the compressor and so the boost pressure. With another words Internal or external, a turbo actuator is a boost-controlling device that operates by limiting exhaust gases going through the turbocharger, controlling the maximum boost pressure produced by the turbocharger itself. A turbo actuator consists of an inlet and outlet port, a valve and a pressure actuator. This helps to protect the turbocharger from unnecessary wear, by capping the maximum boost pressure of the turbo at a safe level.