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Mass air flow limitation

Mass air flow limitation


Maximum engine torque

The engine torque curve is stored in the control module memory. The torque curve shows the engine's maximum torque at various rpm.

The torque is directly proportional to mass air flow/combustion.

The torque curve unit Nm is converted to mg air/combustion.

The curve value is the maximum mass air flow/combustion value which the engine variant allows.

Manual gearbox, torque limitation


For reasons of strength, maximum torque must be limited in the lower gear ratios.

The control module calculates which gear is engaged by comparing engine rpm with the speed of the vehicle.

If the gear ratio corresponds to gear 1 or R, the control module reads bus information "Reverse selected" from DICE to distinguish these.

Engine torque is limited to 230 Nm when gears 1 or R are selected. For other gears, engine torque is limited to 350 Nm. The torque value is converted into mg air/combustion and constitutes the maximum value for the mass air flow/combustion allowed by the gearbox.

Automatic transmission, stall limitation


For reasons of strength, maximum torque must be limited when the car is stationary with the brake pedal depressed.

Engine torque is limited to 200 Nm.

The torque value is converted into mg air/combustion and constitutes the maximum mass air flow/combustion value allowed by the automatic transmission.

TCM, torque limitation


For reasons of strength, maximum torque must be limited when changing gear. The TCM continuously sends out information on the bus specifying maximum permitted torque.

The Trionic T7 converts Nm into mg air/combustion. The value comprises the maximum mass air flow/combustion value permitted by the automatic transmission.

Knock limitation


In connection with knock control, the ignition is first retarded in each cylinder. If the mean ignition retardation value exceeds a certain figure, fuel mixture enrichment takes place.

If the mean retardation value continues to rise, the maximum permitted mass air flow/combustion will be reduced.

This reduction is progressive as ignition retardation increases.

The value constitutes the maximum mass air flow/combustion permitted by knock control.

Vehicle speed limitation


When vehicle speed reaches 240 km/h, engine torque will be limited due to limitation of the maximum permitted mass air flow/combustion.

Engine speed limitation


When engine speed reaches 6000 rpm, engine torque is limited due to limitation of the maximum permitted mass air flow/combustion.