On the exhaust side, a Wastegate provides us a means to control the boost pressure of the engine. Some commercial diesel applications do not use Wastegates at all. This type of system is called a free-floating turbocharger.
However, the vast majority of gasoline performance applications require a Wastegate. There are two (2) configurations of Wastegates, internalor external. Both internal and external Wastegates provide a means to bypass exhaust flow from the turbine wheel. Bypassing this energy (e.g. exhaust flow) reduces the power driving the turbine wheel to match the power required for a given boost level. Similar to the BOV, the Wastegate uses boost pressure and spring force to regulate the flow bypassing the turbine.