Operating strategies

OPERATING STRATEGIES

Actuation of gear changes

The change from one gear to the higher or lower gear depends on the accelerator pedal position, the vehicle speed, the engine's characteristic parameters and the driving mode selected by the driver.

The control module sends an ON/OFF signal to the solenoids S1 and S2.

They consent or prevent the oil from reaching the brakes and clutches necessary for obtaining the different transmission ratios, changing their condition from ON to OFF and vice versa as shown in the table below.

The 3rd-4th gear change is prevented when the engine coolant temperature is below 75°C.

The control module has specific gear change programs memorized for each driving mode (NORMAL, SPORT, ICE), which will be described on the following pages in the section relating to the driving modes.

Locking of torque converter (lock-up function)

The engagement of the lock-up clutch for locking the torque converter depends on the gear engaged, the accelerator pedal position, the vehicle speed and the selected driving mode.

The control module sends a duty-cycle signal to the lock-up control solenoid SL, which discharges the oil pressure in the chamber on the flywheel side, causing the clutch to be engaged and the converter to be locked.

The control module has two specific programs for locking the torque converter memorized for the NORMAL and SPORT driving strategies, while for the ICE strategy the torque converter is not locked. These programs are described on the following pages in the section concerning the driving modes.

The converter is not locked under the following conditions:

1. when the control system receives a fault signal from one of the components and executes the recovery strategy;
2. when the brake pedal is pressed and the gearbox input speed is below a certain value;
3. when the throttle valve is closed (accelerator pedal not pressed) and the vehicle speed is below 125 km/h with the selector lever on position D;
4. when the engine coolant temperature is below 75°C.

During the 3rd-4th gear change, with lock-up clutch engaged, the control module sends to the solenoid SL a signal with variable duty cycle, so as to temporarily disengage the lock-up clutch, to improve the quality of the gear change.

Execution of driving mode

The control module is designed to control the operation of the automatic transmission in accordance with three different driving modes.

The three driving modes allow the driver to select the different capabilities of the automatic transmission in accordance with the momentary requirements of use:

• NORMAL to obtain the maximum driving comfort, while minimizing fuel consumption;
• SPORT to obtain the maximum performance of the vehicle;
• ICE to increase driving safety under slippery conditions.