Z Series E85 Z4 3.0Si (N52) ROADST
To make sure that sufficient system pressure is available to open the clutch immediately after the engine is
started, the general module activates the SMG control unit as soon as the vehicle is unlocked. The reservoir
pressure is measured. If reservoir pressure is too low, the hydraulic pump is actuated once only. Once system
pressure is achieved, the hydraulic pump is deactivated again by the SMG control unit. With the "wake-up
signal", the gear lever position indicator in the centre console is activated. If terminal 15 is not activated after
about 15 minutes, the gear lever position indicator is deactivated again.
Gearshift
If a gearshift is initiated in manual or drive mode, the SMG control unit will actuate the corresponding solenoid
valves in the valve block in sequence. The pressurised hydraulic fluid flows into the clutch actuator and
opens/closes the clutch. At the same time, the SMG control unit sends information to the DME control unit that a
gearshift has been initiated and that engine torque must be reduced. In the next step, the gearshift/selector
angle actuator is actuated. The gearshift/selector angle actuator executes the gearshift by simultaneously
moving the selector shaft forwards/backwards and, if necessary, by rotating the selector shaft. If needed, the
gearshift is supported by an increase in engine speed (intermediate throttle). When the gear is engaged, the
clutch will automatically close. The SMG control unit receives the precise clutch position from the clutch travel
sensor. After the gear change, the solenoid valves are actuated without the use of current. The course of the
entire gearshift depends on the pedal sensor position, road speed, engine speed, transmission speed and other
factors (e.g. engine oil temperature).
Just before the vehicle reaches a standstill, the SMG will shift into 1st gear and open the clutch. The
transmission of power between the engine and transmission is broken.
Gearshifts that would result in an excessively high or low engine speed are suppressed.
Driving in drive mode "D" (automatic mode)
•
Constant-speed travel
Continuous changes of the pedal sensor position (opening and closing the throttle) are registered in the
SMG control unit. The control unit then suppresses a pendulum shift between two adjacent gears (up and
down, e.g. on a motorway with constantly changing speed).
•
Upshift suppression
If the throttle is rapidly closed, the SMG control unit will recognise this from the pedal position transmitter
and will then activate upshift suppression. This prevents an undesirable upshift, (e.g. when braking), and
maintains the engine braking effect.
•
Driving uphill
The SMG control unit recognises when the vehicle is driving uphill from the data from the wheel speed
sensors and the accelerator pedal setting, and then prevents unnecessary upshifts and irritating pendulum
shifts (e.g. at constantly high engine speed and foot taken from accelerator pedal).
•
Driving downhill
Signals from the throttle-valve potentiometer (engine load signal), the wheel speed sensors (road speed)
and the brake-light switch (brake in operation) allow the SMG control unit to recognise when the vehicle is
driving downhill. If road speed increases, the SMG control unit will shift down a gear to maintain and
increase the engine's braking effect.
•
Braking deceleration and automatic downshift
The SMG control unit recognises braking deceleration from the brake-light switch, the wheel speed sensors
and the accelerator pedal setting. The SMG control unit shifts down according to road speed to maintain the
engine's braking effect. As this happens, several gears may be skipped. The correct gear is automatically
selected when the vehicle accelerates again.
SBT Sequential manual transmission SMG, based on GS6-37BZ E85
BMW AG - TIS
18.02.2013 04:10
Issue status (12/2007) Valid only until next DVD is issued
Copyright
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