Engine Performance: System: Turbocharger: Operation: Notes
On vehicles equipped with manual transmissions, and with fuel selector switch in regular unleaded position, boost pressure is limited by wastegate to approximately 10 psi (.71 kg/cm2 ). Wastegate opens if boost pressure reaches 10 psi (.71 kg/cm2 ), by-passing exhaust gasses away from turbine blades, thus limiting turbo boost pressure.
When fuel selector switch is in premium position, the EEC module sends open and close commands to the turbo boost control module which, in turn, energizes or de-energizes the solenoid. When solenoid is energized, a portion of the pressure signal to wastegate actuator is diverted to inlet side of the boost solenoid. This results in higher boost pressures of 13-16 psi (.92-1.14 kg/cm2 ) maximum. Boost pressure varies depending on RPM, vehicle speed and transmission gear selection.
On vehicles equipped with automatic transmissions, the boost control solenoid operation does not change with fuel selector switch mode, either in premium or regular positions. Solenoid operation is similar to the operation for premium position on vehicles equipped with manual transmissions, except boost pressures are lower. Boost pressure is 8-11 psi (.57-.78 kg/cm2 ) maximum. Boost pressure varies between 6-11 psi (.43-.78 kg/cm2 ) depending on RPM and vehicle speed.