Patent ID: 8276378

Claim:
A method for controlling an engine including a turbocharging system with a high pressure turbocharger and a low pressure turbocharger, comprising: in a first load-engine speed region, operating a variable nozzle turbine of the high pressure turbocharger in a transient position by performing closed loop control of the variable nozzle turbine based on boost pressure, and operating a high pressure turbine bypass valve in a closed position; in a second load-engine speed region between the first load-engine speed region and a third load-engine speed region, operating the variable nozzle turbine in a maximum open position, and operating the high pressure turbine bypass valve in a transient position by performing closed loop control of the high pressure turbine bypass valve based on a position of the high pressure turbine bypass valve and a measured current flowing to the high pressure turbine bypass valve; and in the third load-engine speed region, operating the variable nozzle turbine in a transient position by performing open loop control of the variable nozzle turbine based on boost pressure, and operating the high pressure turbine bypass valve in a transient position by performing closed loop control of the high pressure turbine bypass valve based on the position of the high pressure turbine bypass valve.