This type of wastegate is an integral part of the exhaust housing. It consist of a flapper door inside of the exhaust housing that is controlled by a vacuum/boost referenced actuator valve that is attached to the compressor housing. Most OE manufacturers use this type of set-up because it is cheap and there are no fitting problems like those of external wastegates. Because of the flapper door size this type of wastegate is not efficient at high boost levels . Since it can not relieve enough exhaust flow to maintain the maximum boost setting boost creep will sometimes occur when driven hard. Most actuators are pre-set from the factory with maximum boost level that can not be adjusted unless a boost control device is added .There are after market racing actuators on the market have an adjustable rod that allows for boost level changes.

This type of wastegate is also vacuum/boost referenced but it is separate entity from the turbine section. External wastegates are connected in many different ways but the most efficient method is to connect it with it's own section of piping near the collector flange of the manifold. This type of connection will allow exhaust flow to be drawn from all primary tubes equally. Of course this type can not be applied to all street cars because of the space limitation factor. The physical size of the wastegate valve, which is 35mm or larger for small external wastegates, and connection point makes the external wastegate a better choice for mild to wild set-ups. If the the dump tube for the wastegate is to be routed back into the exhaust piping for a closed loop set-up it is best to make the tube as long as possible. Flow from the wastegate tube that is re-entered back into the exhaust too early can cause a restriction in flow by creating back pressure. This should be taken into account when fabricating the exhaust downpipe.