CITROEN DS series Technical Manual page 30

U
The Citroën Guide
SOFT MODE
4
strut
5
return
control from
computer
security
valve
HARD MODE
4
strut
5
return
control from
computer
security
valve
lets the pressure inside the center sphere 1 move the con-
trol piston into a position which closes off the center sphere
completely.
The center sphere 1 is now supplied directly from the
height corrector in soft mode. This simplifies the ball valve
arrangement with respect to Hydractive I.
Higher intelligence
The computer uses the same set of sensors as Hydractive I,
the only difference is the vehicle speed sensor which is a
Hall-effect sensor now. Its resolution have been doubled to
8 pulses generated per rotation, that is approximately 5
pulses per meter traveled (although this depends some-
what on tire size). It is located on the gearbox where the
speedometer cable attaches, or in some versions, on the ca-
ble itself.
Suspension: Hydractive II
1
2
4
3
suspension pressure
height
system feed pressure
corrector
1
2
4
3
suspension pressure
system feed pressure
height
residual pressure
corrector
The internal algorithm of the computer became more so-
phisticated. While the Hydractive I had only one computer
controlled mode (Sport switched the suspension to con-
stant hard mode above 30 km/h of vehicle speed), the
newer system has two such regimes of operation: in both
Normal and Sport it dynamically activates the electro-valves
of the suspension control blocks whenever it decides that
the driving circumstances call for a firmer suspension. The
difference is in the set of rules the computer uses to evalu-
strut
ate those circumstances: the rules are stricter for the Sport
setting, with most of the thresholds reduced, thus the sus-
pension will switch to hard mode much more readily.
The following table shows the thresholds of steering
wheel angle. If the value observed by the sensor exceeds
the threshold for the actual vehicle speed and the suspen-
sion setting, the suspension will switch to hard mode; it will
revert to soft when the corresponding value drops below
the threshold for at least 1.5 seconds:
Steering wheel
Vehicle
angle (deg)
speed
(km/h) Normal
< 34
34–39 174
40–49 100
50–59
60–68
69–78
79–89
There is a similar table for the thresholds of the steering
wheel rotational speed as well:
strut
Steering wheel
Vehicle
speed (deg/s)
speed
(km/h) Normal
< 24
24–29 535
30–39 401
40–49 246
50–59 178
60–68 110
69–78
The thresholds for body movement are:
Vehicle
Dive
speed
(mm)
(km/h)
< 10 —
10–33 84
34–39 84
40–49 54
50–59 54
60–68 54
69–78 54
79–89 54
90–99 48
Note that the thresholds are the same for both Normal and Sport suspension settings
The thresholds of the gas pedal sensor are:
Vehicle
speed
Sport (km/h)
— — 90–99
119 100–119
67 120–139
84 56 140–158
68 45 159–179
55 37 179 >
42 28
Vehicle
speed
Sport (km/h)
— — 79–89
357 90–99
267 100–119
164 120–139
119 140–158
73 158 >
82 55
Steering Vehicle
Squat
wh pos speed
(mm) (mm)
(deg) (km/h)
— — 100–109
60 — 110–119
60 87 120–129
48 50 130–139
48 42 140–149
48 34 150–158
48 27.5 159–179
48 21 179 >
48 16.5
30
Steering wheel
angle (deg)
Normal Sport
33 22
26 27
23 15
20 13
13 9
10 7
Steering wheel
speed (deg/s)
Normal Sport
62 41
53 35
42 28
30 20
22 15
20 13
Steering
Dive Squat
wh pos
(mm)
(deg)
48 48 13
48 42 13
48 42 11.5
42 42 11.5
42 42 10
42 36 10
42 36 6.5
36 36 5