Turbo Control System

Turbo Control System

The flow of air from the turbo compressor is controlled by a solenoid valve which pneumatically controls the wastegate for the exhaust turbine.

The solenoid valve is supplied with current from the +15 circuit and grounded via control module pin 13 with a 32 Hz PWM signal. The compressor flow increases as the pulse ratio increases.

If the requested mass air flow-combustion is too large to be controlled by the throttle alone, the turbo control system must provide the extra requirement. The excess is converted into a PWM signal which controls the charge air control valve.

The absolute barometric pressure and the temperature of the intake air are used to correct the conversion. At low barometric pressure or high intake air temperature, a higher PWM ratio is required to achieve the same mass air flow/combustion.

The control module then checks that the current mass air flow-combustion corresponds to that requested. If necessary, fine adjustment of the PWM ratio is performed by multiplying it by a correction factor.

The correction factor (adaptation) is stored in the control module's memory and always included in the PWM ratio calculations.

The aim is for the current mass air flow/combustion to equal that requested as soon as possible after a load change. The limit value for adaptation is 100%.

Diagnostics
- In the event of a break or short-circuit to ground, diagnostic trouble code P1662 will be generated.
- In the event of a short-circuit to B+, diagnostic trouble code P1663 will be generated.

System reaction to a fault
- Charge air adaptation is blocked.
- In regard to other turbo control system faults, the diagnostic tool will be of great help in obtaining a readout of charge air adaptation.

NOTE: The system controls the current mass air flow/combustion so that it corresponds to the requested value. It is perfectly normal for the throttle valve not to be fully open despite the accelerator being pressed fully down.