Principle of Operation: ASC
The system is controlled by the ASC control unit (which replaces the ABS control unit) and is permanently active when the vehicle is being driven. The driver can disable ASC through the switch panel mounted switch. ASC is fitted as standard to MINI COOPER S version and is available as a factory fitted option on all other versions of the MINI.
The prevention of wheel spin is achieved by engine torque reduction and/or brake application. To prevent one wheel spinning, brake application to that wheel is employed and to prevent both wheels spinning, engine torque reduction is employed. These processes occur within milliseconds.
The ASC control unit checks for wheel spin by comparing the speed of each front driven wheel with the speed of the rear wheel on the same side. With this information, the ASC control unit determines whether brake application or engine torque reduction is appropriate. If brake application is required, the hydraulic unit isolates the brake line to the appropriate driven wheel and hydraulic pressure is applied in that brake line until the speed of the wheel returns to a value acceptable to the control unit. The return pump that takes its fluid supply from the master cylinder reservoir provides hydraulic pressure.
If engine torque reduction is also required, the ASC control unit sends the necessary command to the Engine Management System (EMS) control unit. A torque change request from the ASC control unit takes priority over any other torque change request received by, or generated internally within, the EMS control unit. Torque reduction is limited to the minimum value necessary to prevent wheel spin. The ASC control unit constantly updates the EMS control unit to ensure that driver demand' for acceleration is restored as soon as conditions permit.
The ASC warning lamp in the instrument cluster will flash when the system is operating. The warning lamp is illuminated permanently if the driver has switched off the ASC system or if the ASC control unit has detected a fault with the system. The need to switch off the ASC system should only be necessary under unusual circumstances such as driving away in snow or muddy conditions. The system must be switched off when snow chains are in use.