Sooviks infot 4WD kohta.

[meego]

Siin siis täielik seletus 124 4matic´u kohta:

If speed differences occur at the wheels, the fourwheel
drive is engaged in drive and overrun mode
when driving backwards and forwards.
Essentially the following criteria apply for the
engagement and disengagement of the four-wheel
drive and the two differential locks:
- Drive skid
- Vehicle speed
- Acceleration
- Steering angle
- Time
- Operating the service brake
The 4MATIC control unit (N30/3) receives the
necessary signals via:
- Speed sensors on the front wheels and on
- Rear axle center piece assembly
- Steering angle sensor on steering wheel
- Stop lamp switch
The following 4MATIC shift stages are engaged in
accordance with a predetermined logic using these
signals:
0 - Rear-wheel drive (basic drive)
1 - Four-wheel drive compensated with 35/65%
front/rear torque distribution
2 - Four-wheel drive locked inter-axle
3 - Four-wheel drive locked inter-axle and interwheel
The incoming signals are processed in accordance
with the following criteria in the logic section of the
4MATIC control unit (N30/3):
Drive skid
If differences between the mean front and rearwheel
speeds occur, this is recognized as skid and
the front-wheel drive shift stage 1 is engaged.
If there are still speed differences, shift stage 2 is
engaged as the next step and shift stage 3 below
38 km/h, if required.
The following shift thresholds are determinate for
engagement of stage 1:
Speed difference Vehicle speed
(wheel speed difference)
>2 km/h <100 km/h
>2% >100 km/h
Four-wheel drive and differential locks remain
engaged provided the engagement criteria exist. If
they no longer exist, the differential locks are
released in sequence after a brief holding time of
approx. 0.7 s.
Alearning effect for starting-off is included in the
4MATIC control unit (N30/3):

The 4MATIC control unit (N30/3) recognizes an
unsuccessful attempt at starting off such that a
speed of 5 km/h is not exceeded within 0.5 s. It
then engages both differential locks (shift stage 3)
in addition to the permanent four-wheel drive (shift
stage 1) for the next start. The ASD/4MATIC
function indicator lamp (A1e25) comes on
permanently and only goes out 0.5 s after shifting
back into shift stage 0 (rear-wheel drive). The
differential locks are released at 10 km/h if the
engagement criteria no longer exist.
Vehicle speed
When starting off, up to a speed of at least 20
km/h, the four-wheel drive, i.e. shift stage 1 is
engaged (no function indicator!). Shift stage 3 is
no longer engaged over 35 km/h.
Acceleration
When starting off with rapid acceleration (more
than
0.5 m/s2) the four-wheel drive (shift stage 1)
remains engaged at more than 20 km/h provided
the acceleration is maintained.
Steering angle
If transverse skid occurs due to a sudden change
of road surface adhesion whilst cornering or due to
sharp steering movements, the compensated fourwheel
drive shift stage 1
engages at speeds above 30 km/h, thus stabilizing
the vehicle during cornering. A deviation of the
radius of the curve driven to the course
preselected by the driver is detected by the
4MATIC control unit (N30/3) from the speed
differential between the left and right front wheel
and the recorded steering angle. If the speed
differential between the front wheels exceeds the
speed-dependent value calculated from the
steering angle, shift stage 1 is engaged.
Time
If shift stages 1, 2 or 3 are engaged more often
within a predetermined time period, the holding
times for the respective shift stages are extended
thus avoiding a constant engagement and
disengagement of the front-wheel drive and
differential locks.
Operating the service brake
The 4MATIC control unit (N30/3) receives signals
via the stop lamp switch (S9/1) that the driver is
braking and immediately engages shift stage 0
(rear-wheel drive). The driving stability during
braking and full ABS function is thus retained. Only
when braking from speeds below
5 km/h and when starting off is interrupted by
braking up to a speed of 10 km/h, does shift stage
1 remain engaged.