Wastegate

A valve that diverts exhaust around the turbine to cap how much boost a turbocharger can build.

A wastegate is a valve, internal or external, that bleeds exhaust gas around the turbine wheel to limit turbine speed and therefore cap boost. It is the primary boost-control actuator on a turbo system. A spring sets the base pressure, and a boost-control solenoid driven by the ECU modulates how much pressure the wastegate actuator sees, letting the tune raise boost above spring pressure. This is where commanded versus delivered matters most: you tune wastegate duty cycle to chase a boost target, but the actuator, spring, and exhaust energy determine what actually happens. Watch for overboost spikes and boost creep. In VCM Editor, boost-control tables appear as wastegate duty cycle or boost target maps on supported turbo platforms. In VCM Scanner, log Wastegate Duty, Boost Target, and actual MAP together so you can see the controller converging. Tune duty in small steps and verify with a wideband.