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Other air request

Other air request





Idle speed control

When the accelerator is fully released and vehicle speed is zero, the system regulates the mass air flow/combustion required to ensure that the current idling speed corresponds to that requested. The air requirement is stored in the control module's memory (adaptation). The requested idling speed is stored in a table in the control module's memory and is dependent on the temperature of the coolant

At -30 °C, the value is 1200 rpm and as the engine heats up, the requested idling speed drops to 700 rpm.

DICE sends bus information: “Fast Idle Speed”. The value is used by Trionic. DICE sends “ON” if radiator fan high has been activated at any time during the present driving cycle. The requested idling speed then gradually increases to 750 rpm to increase the efficiency of the generator and the A/C compressor.

TCM sends bus information “Selector lever position PRND321”. The value is used by Trionic.

When any value other than P or N is selected, the requested mass air flow/combustion is increased to compensate for the impending load increase. The purpose of this is to compensate fully for the automatic transmission's increased torque requirement to avoid a sudden drop in idling speed before the idle speed control can compensate for this. The air requirement in any position other than P or N is stored in the control module's memory (adaptation).



As soon as the car begins to move, the idle speed control is disabled and the engine receives the adapted air quantity.

Dashpot

The dashpot function is activated when the accelerator pedal is released to lower the mass air flow/combustion smoothly.

Basic Load

When the dashpot function has finished, the engine receives the adapted idle air quantity. If this is insufficient to ensure combustion, the basic load function will be activated.

Diagnostics

Information on the difference between requested idling speed and current speed, and whether the idle speed control is active or not, can be obtained using the diagnostic tool.