Part 3

-Continued From Part 1-

Adaptive transmission control
As with earlier automatic transmissions, the 6-speed automatic transmissions offer the choice between a comfort program and a sport program.
The adaptive transmission control (component of electronic transmission control) adapts the shift characteristics of the comfort program and sport program to the driver's wish and the driving situation.

In both programs, the adaptive transmission control changes from a basic map to a performance-orientated map, as required:
- Comfort program in selector lever position "D"
The comfort program is based on 2 maps: The XE map (extreme economy) and the E map (economy). The EGS control unit normally selects the economical XE map (= basic map). In case of particular demands (e.g. load requirements), the system will change to the performance-orientated E map. If the input signals change in favour of a more gentle driving style, the system will change back to the more economical XE map.
- Sport program in selector lever position "M/S"
The sport program effects dynamic, sporty shift characteristics. In the sport program, there is the basic S map (sport) and the performance-orientated XS map (extreme sport). If an extremely dynamic driving style is called for, the system will change from the S map to the performance-orientated XS map.
The adaptive transmission control takes the following demands into account:
- Adaptation to driver type
- Driving uphill or trailer towing
- Driving downhill
- Braking deceleration and automatic upshift
- Winter program



Adaptation to driver type
The adaptation to different driver types is done using the following values:
- Kick-fast
If the accelerator pedal is depressed rapidly, the shift program is changed accordingly. This is achieved by the detected accelerator-pedal value being compared with threshold values in the EGS control unit. The result of this comparison is the proposal of one of the two possible programs (XE or E in comfort program, S or XS in sport program).
- Cornering detection
Cornering detection reacts to the vehicle's lateral acceleration with an indirect adaptation to the driver type.
Lateral acceleration is considered an indirect statement of the preferred driving dynamics and does not cause an immediate gearshift response (shifts when cornering could adversely affect driving stability).
Lateral acceleration is calculated from the signals from the wheel-speed sensors, from the yaw rate and road speed.
- Brake evaluation
The braking action is evaluated in a similar way to "kick-fast".
The braking deceleration is measured and compared with threshold values in the EGS control unit. The result of this comparison is the proposal of one of the two possible programs (XE or E in comfort program, S or XS in sport program).
The driver-type adaptation is restarted each time the vehicle pulls away from a standstill.



Driving uphill or trailer towing
These functions are based on a comparison of actual car acceleration with a nominal value. From the current engine operating situation, the acceleration with normal load on a level surface is calculated. If the actual acceleration is significantly below the theoretical value, the "Driving uphill or trailer towing" function is activated.
The design of the corresponding shift characteristics allows a high-speed driving style. Undesirable upshifts and frequent up/downshifts are eliminated or greatly reduced.



Driving downhill
If the EGS control unit detects downhill driving, it will automatically shift down a gear if the vehicle's speed picks up. This enhances the engine's braking effect. A downshift is only effected if the engine speed is below the maximum speed of the lower gear.
The EGS control unit detects downhill driving on the basis of signals from the throttle valve potentiometer (load), wheel speed sensor (road speed) and brake light switch (brake activation).



Braking deceleration and automatic upshift
To decelerate the vehicle, the foot is taken off the gas and the brake depressed as necessary. The gearshift map triggers an upshift when the throttle is closed. These gearshifts are not necessary in conjunction with brake applications as they prevent the engine's braking effect from being exploited.
The intention to apply the brakes can often be anticipated from the accelerator pedal being rapidly released to the zero position. If such an action is detected, the upshift is suppressed for as long as the accelerator pedal is in the zero position and the vehicle is in overrun mode.



Winter program (only with selector lever in position "D")
The winter program is automatically activated if the drive wheels start to spin even at a low rate of acceleration. The winter program ensures better traction by not using 1st gear. Early upshifts reduced the reactions caused by load changes. The winter program is deactivated if the wheels do not spin for several seconds despite high drive torque.



Overlap control
Overlap control provides gentle shift characteristics as follows: With overlap control, several multi-plate clutches are in use at the same time. Here, pressure is reduced in the active multi-plate clutch and at the same time built up in the clutch that is about to be activated. The reduction and build-up of pressure is maintained until a synchronised speed is reached. At this point, the hydraulic pressure for the multi-plate clutch to be activated can be built up completely. Overlap control is active for all gearshifts from 1st to 6th gear and from 6th to 1st gear.



Starter inhibitor
It is only possible to start the engine when the selector lever is in position "P" or "N".

> E53, E83, E85, E86
The EWS (electronic immobiliser) evaluates the following signal from the EGS (electronic transmission control) for the start:
- Selector lever position "P" or "N" as signal via the direct wire
> E60, E61 until 03/2007
> E63, E64 until 09/2007
> E81, E87, E90, E91, E92, E93
The CAS (Car Access System) evaluates the following signals from the EGS (electronic transmission control) for the start:
- Selector lever position "P" or "N" as CAN message via the powertrain CAN
- Selector lever position "P" or "N" as signal via the direct wire
> E60, E61 from 03/2007
> E63, E64 from 09/2007
> E65, E66, E70
The CAS (Car Access System) evaluates the following signals from the EGS (electronic transmission control) for the start:
- Selector lever position "P" or "N" as CAN message via the powertrain CAN
- Selector lever position "P" as signal via the direct wire
In principle, the CAN message is used. If the message is incorrect or invalid, it switches to the signal from the direct wire.



Parking lock
The parking lock locks the transmission output shaft. The vehicle is prevented from rolling unexpectedly. The parking lock is designed to provide a reliable brake on gradients up to 32 %.

> E53, E81, E83, E85, E86, E87, E90, E91, E92, E93
> E60, E61 until 03/2007
> E63, E64 until 09/2007
When the vehicle is stationary, the parking lock is engaged purely mechanically via the selector lever (Bowden cable from selector lever to mechatronics module).

> E65, E66, E70
> E60, E61 from 03/2007
> E63, E64 from 09/2007
With the electric version of the parking lock, the parking lock is applied and electrically secured via a mechanical spring system in the transmission.
The parking lock is activated under the following conditions:
- E65, E66,
- Pressure on the button on the selector lever and roadspeed signal less than 2 km/h.
- Remote control removed from the slot and road speed signal 0 km/h.
- Engine ON
and
Transmission position "D" or "R"
and
Driver's door open
and
Driver's seat not occupied
(road speed signal less than 2 km/h).
- By pressing the START/STOP button while the engine is ON (change status of terminal 15 to OFF)
and
Transmission position "D" or "R"
and
Road speed signal 0 km/h.
- E60, E61 E63, E64, E70
- Pressure on the button on the selector lever and roadspeed signal less than 2 km/h.
- Remote control removed from the slot and road speed signal 0 km/h.
- Engine ON
and
Transmission position "D" or "R"
and
Driver's door open
and
Driver's seat belt not fastened in belt buckle
and
Pedals not depressed
(road speed signal less than 3 km/h).
- By pressing the START/STOP button while the engine is ON (change status of terminal 15 to OFF)
and
Transmission position "D" or "R"
and
Road speed signal 0 km/h.
The parking lock is only released when the engine is ON. Reason: Only when the engine is ON is there enough hydraulic pressure to open the parking lock (mechanical emergency release possible).

> E65, E66, E70
If the parking brake (EMF = "electromechanical parking brake") fails, the parking lock can still be applied.
Example: A fault in the system prevents the parking brake from being moved from "Hold" to "Park". In this case, the EGS control unit will engage the parking lock after a prompt from the DSC (master control unit for the electromechanical parking brake) and after a plausibility check.
The locking conditions are as follows:
- E65, E66
- Selector lever in position "N"
- Speed 0 km/h
- Engine OFF and ignition OFF
- E70
- Selector lever position "D" or "N" or "R" engaged
- Speed 0 km/h

-Continued in Part 3-