An exhaust gas turbocharger with a wastegate port configured to permit some exhaust gas flow to exit a turbine volute upstream of the turbine wheel and enter a bypass channel thereby bypassing the turbine wheel, a valve with a valve head dimensioned to seat on a valve seat and to move between a seated position and an open position, the bypass channel having a sidewall contoured to surround the valve head as the valve head moves between the seated position and the open position, he bypass channel sidewall shaped so that a throat area (At) area between the bypass channel sidewall and valve head gradually increases as the valve head moves between the seated and the open position, such the bypass flow is controlled by the throat area (At) and not the area between the valve head and the valve seat.