Brief description - RA3000TPM0002X(30-0002)
Electronic accelerator (EA) with cruise control (CC) and idle speed control (ISC)
The electronic accelerator (EA) works in conjunction with the acceleration skid regulation (ASR) and improves the capacity for starting off and accelerating as well as driving stability.
The EA works in the drive moment control circuit and the ASR in the brake moment circuit. Both control circuits prevent the wheels spinning when starting off and accelerating.
If the set slip threshold of the drive moment control is exceeded while driving i.e. one or both rear wheels spin, the ASR/ABS control module instructs the EA control module to reduce the throttle.
Achieved by controlling the EA actuator, the throttle valve opening is achieved "independently" of the accelerator pedal position
Slip threshold
The drive moment is thus controlled by closing, holding and opening the throttle valve.
If the differential speed ( Δv ) drops below the slip threshold, the throttle valve is opened in accordance with the accelerator pedal position
A distinction is made between three control ranges in ASR/EA control mode:
- Control mode when a driving wheel spins and the vehicle speed is < 40 km/h
Here the slip threshold of the drive moment control is higher than that of the brake moment control. In the event of actuation, the brake moment control is thus activated first . If the driving wheel still spins faster, the drive moment control is also activated. Priority is given to maximum traction.
- Control mode when both driving wheels spin or at a vehicle speed > 40 km/h
In this case the slip threshold of the brake moment control is above that of the drive moment control.
Initially the throttle valve position is reduced in the event of a control. If the wheels still spin faster, the brake moment control is also activated. Thus priority is given to maximum stability.
- Control mode when cornering at vehicle speeds between approx. 20 km/h and 120 km/h
In this case, depending on the lateral acceleration, the drive moment control comes into operation even sooner than for control mode B. This increases directional stability during cornering.
Increase in slip threshold
In deep snow and with snow chains, the sensitive, stability-orientated control of ASR can have a detrimental effect on the starting-off characteristics. Therefore a specific control logic has been programmed in for the starting off range in such situations which can be selected by the driver via the snow chain switch (S76).
By increasing the slip threshold, the vehicle can bite its way out in deep snow when snow chains are fitted, thus achieving maximum traction. For reasons of vehicle stability, this control is only permitted in the speed range up to 40 km/h.
The slip thresholds are increased in stages after 50 ms control mode in the lower speed range < 40 km/h.
The increased slip threshold remains stored up to 60 km/h, it is erased above this speed.
A greater differential speed between the front and rear wheels is permitted due to the increase in slip thresholds.
Malfunction/function indicator
When the engine is running, the malfunction indicator lamp (A1e22) indicates whether there is a fault in the ASR/EA system.
Models 124, 129, 140
The function indicator lamp (A1e21) lets the driver know when ASR intervenes and provides a signal to the driver that he is driving the vehicle close to its limits.
The function of the ASR is affected by ABS as ASR control mode is interrupted when braking.
Model 202
Fault memory
All system components are permanently monitored by the monitoring system in the EA control module and any faults are stored in the fault memory of the control module. The faults can be read out via a test coupling (for details, refer to chapter on detailed description).
Driving with ASR/EA
When the ignition is switched on, function indicator and malfunction indicator lamps in the instrument cluster (bulb check) come on and go out when the engine is running.
Driving mode
In driving mode, the function indicator comes on as soon as ASR operates. After ASR control mode is complete, the function display stays on for about another second. The function indicator does not come on during a very brief ASR control intervention.
Control mode
The function indicator lets the driver know that control mode has been activated and signals to the driver that he is driving the vehicle close to its physical limits. He can thus better adapt his driving style to the prevailing road conditions.
Data bus (CAN)
The control modules are interconnected so that information can continuously be exchanged between:
- DI/KSS ignition control module (on engines with LH-SFI injection system only)
- ABS/ASR control module
- EA control module
- AT control module, 5-speed
- Diagnostic module (
only)
- Injection system control module
Limp-home mode
In the event of faults in the EA, the system is switched off, the accelerator pedal goes into mechanical emergency-running operation. When the throttle is opened, it is now only operated mechanically, the throttle valve only being able to be opened approx. 2/3.
In addition, the electronic limp-home mode is activated in the event of faults in the safety contacts, i.e. the engine speed is limited to approx. 1200 rpm by shutting off the fuel supply (safety fuel shut-off). It is possible to continue driving in both cases (refer to chapter on Individual Functions).
Cruise control (CC)
The cruise control function is integrated in the EA control module. It is activated or switched off via the Cruise control switch (S40). Using the cruise control, any speed above approx. 40 km/h can be maintained by operating the cruise control switch.
Cruise control cannot be activated if the switch is operated during braking or the speed is < 40 km/h. The position controller receives an appropriate input signal when the cruise control is set and as a result the position of the throttle valve is specified. If the driver requires a higher speed via the accelerator pedal, the cruise control system remains inoperative (refer to chapter on Individual Functions).
Idle speed control (ISC)
The idle speed function is integrated in the EA control module. Model 140 with engine 104 LHSFI without EA or CC has a separate control module (N4/4) for idle speed control.
On vehicles with HFM-SFI injection systems without EA or CC, the idle speed control module is integrated in the HFM-SFI injection system control module.
If idle speed deviations are detected during the specified/actual value comparison, the position controller in the control module receives an appropriate input signal and the position of the throttle valve is now specified.