Torque control, basic function

Fig 1: Identifying Torque Calculation (Driver Request)

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The control module reads the voltage from pedal potentiometer 1 and converts it to a torque request.

With cruise control active, the torque required to maintain the set speed is calculated.

1x requests torque to keep the engine running. The highest value (select high) of functions 10 (pedal) and 11 (cruise control) is selected. Function 12 (idle) gives torque to keep the engine running when the pedal is released and cruise control (11) is inactive.

2x are torque limitations of what is requested from the box above. Here, the lowest value (select low) of 1x and 2x is selected. Maximum torque varies depending on the engine variant. Furthermore, engine torque when driving must be limited to protect the engine, gearbox, brakes and turbocharger. Even external units such as TCM or TCS/ESP can limit engine torque. Engine torque is also limited by certain system faults.

Control module selects lowest value.

Fig 2: Identifying Torque Calculation (Vehicle Speed)

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Engine torque can be limited to limit the maximum speed (31) of the car.

Control module selects lowest value from function 2x and limitation of vehicle speed, 31.

If requested torque is lower than is necessary to maintain stable combustion, if the wheels slip during engine braking or if dashpot is required, the engine torque can be increased slightly. Request is sent to box 11.

Control module selects highest value.

Fig 3: Control Module Highest Value

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Engine torque can be reduced to protect the engine from e.g. knocking.

Control module selects lowest value.

This function dampens rapid changes in torque request to reduce transient enrichment.

7x is a Select Low together with maximum permitted air mass/combustion when pedal released. Only for safety and as a final check. This result is the total air mass that is to pass the engine per combustion.

Control module selects lowest value.

Fig 4: Control Module Lowest Value

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Compensation for the torque required for e.g. A/C compressor and generator operation.

The control module totals all the values.

This value is the system's total torque request.

Conversion torque (Nm) to air mass/combustion (mg/c).

Fig 5: Conversion Torque To Air Mass/Combustion

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Requested air mass per combustion is converted to a voltage for throttle potentiometer 1. Charge air pressure and temperature are used to correct the conversion. The throttle motor turns the throttle until the value for throttle potentiometer 1 agrees with the requested value.

Requested air mass/combustion is compared with the current air mass/combustion (MAF actual). In case of a deviation, the requested voltage for throttle position sensor 1 will be adjusted.

If the requested air mass/combustion is too great to be handled by throttle control only, control will be transferred to the turbo control. The excess is converted to a PWM that controls the charge air control valve.

The value is corrected by the value from the atmospheric pressure sensor.

The requested air mass/combustion is compared with the current air mass/combustion and the charge air control valve PWM is adjusted if necessary.