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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.

Automatic transmission, limitation in reverse


When selector position R is selected, an engine speed-dependent torque limitation takes place. This is to reduce the load on the power train mountings.

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.

Braking


For reasons of strength, the maximum torque is limited when the brake pedal is depressed. The following three conditions must be fulfilled before the function is activated:


• B+ on the input from the brake light switch, pin 63.

• B+ on the input from the brake and clutch pedal switches, pin 29.

• Brake lights ON (Bus from Twice)


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.

Traction Control, engine torque limitation





The Traction Control function is integrated in the TC/ABS control module.

TC/ABS receives three signals from Trionic T7:


• Engine torque, 100Hz PWM from pin 61 to TC/ABS control module pin 27.

The various pulse ratios have different meanings:

- 5%: Engine stationary.

- 9-92%: Engine running and engine torque between -100 Nm and 410 Nm.

- 96%: Trionic has detected a fault that affects the TC/ABS function (see Diagnostics).

TC/ABS uses the engine torque limitation value to calculate the current drive wheel torque.

• Pedal position, 8Hz PWM from pin 14 to TC/ABS control module pin 12.

Three different pedal positions are indicated by varying pulse ratios. When the pedal is depressed 0-47% the pulse ratio is 16%, at 47-72% the pulse ratio is 40% and at 72-100% (Kickdown) 64%.

TC/ABS uses the value to determine how much wheelspin to allow.

• Engine speed, frequency modulated signal from pin 28 to TC/ABS control module pin 30.

Trionic grounds the lead twice per crankshaft revolution.

TC/ABS uses the value, together with the vehicle speed, to calculate the current gear ratio. Given the engine torque and current gear ratio, TC/ABS can calculate the drive wheel torque.







TC/ABS sends one signal to Trionic T7:


• Engine torque limitation, 100Hz PWM from TC/ABS control module pin 13 to pin 41.

The various pulse ratios have different meanings:

- 88-90%: Increase torque to 10 Nm.

- 86-88%: Increase torque to 0 Nm.

The two values above are sent if wheel slip occurs during engine braking.

- 84-86%: No wheel slip and TC/ABS programmed for V6.

- 82-84%: No wheel slip and TC/ABS programmed for 4 cyl.

The two values above are sent so that Trionic T7 can determine whether the TC/ABS control module is programmed for the correct engine variant.

- 9-82%: Limit torque to between -100 and 350 Nm

Trionic T7 converts Nm to mg air/combustion. The value constitutes the maximum value for mass air flow/combustion allowed by TC/ABS.


Diagnostics

Trionic can detect three different faults that affect the function of the TC. Trionic will then send a 96% pulse ratio engine torque signal to inform the TC/ABS, which then generates a diagnostic trouble code and turns on the TCS OFF lamp. The three faults are:


• Trionic is not receiving pulses on the lead for engine torque limitation while the ignition is on (open circuit or short circuit in the lead).

• Trionic detects that TC/ABS is programmed for the incorrect engine variant (the programmed variant is sent from TC/ABS on the lead for engine torque limitation).

• Fault in the Trionic throttle control (limp-home). If this fault occurs, the CHECK ENGINE lamp will also go on. The cause of the fault is in Trionic.


Note

No diagnostic trouble codes or fault symptoms occur in Trionic due to a fault in TC/ABS or in the leads between the control modules.


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.

Turbo speed limitation


At low barometric pressures, the maximum permitted mass air flow/combustion is limited to protect the turbo from overrevving.