10x / Техника / Автомобили / Citroen

Hidroactive II

The electro-valve 5 is energized when the suspension is in
its soft mode, hence, the default electrical position is hard.
However, due to the indirect coupling between this valve
and the isolation piston 2 inside the control block, the hydraulics
can stay in either position for extended periods of
time with the electric valve disconnected, depending on the
pressure differences between the strut and the main circuits.
If the main suspension circuit has nominal pressure,
the system stays in hard mode with the electric valve off or
disconnected.
The two modes are practically the same as on the previous
Hydractive system: in soft mode the electro-valve 5
opens the feed pressure onto the isolation piston 2 and by
moving it, connects the center sphere 1 to the rest of the
suspension. In hard mode, the electro-valve 5 closes and

The internal algorithm of the computer became more sophisticated.
While the Hydractive I had only one computer
controlled mode (Sport switched the suspension to constant
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 evaluate
those circumstances: the rules are stricter for the Sport
setting, with most of the thresholds reduced, thus the suspension
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 suspension
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:

Vehicle
speed
(km/h)
Steering wheel
angle (deg)
Normal Sport
< 34 — —
34–39 174 119
40–49 100 67
50–59 84 56
60–68 68 45
69–78 55 37
79–89 42 28

Vehicle
speed
(km/h)
Steering wheel
angle (deg)
Normal Sport
90–99 33 22
100–119 26 27
120–139 23 15
140–158 20 13
159–179 13 9
179 > 10 7

Vehicle
speed
(km/h)
Steering wheel
speed (deg/s)
Normal Sport
24 — —
24–29 535 357
30–39 401 267
40–49 246 164
50–59 178 119
60–68 110 73
69–78 82 55

Vehicle
speed
(km/h)
Steering wheel
speed (deg/s)
Normal Sport
79–89 62 41
90–99 53 35
100–119 42 28
120–139 30 20
140–158 22 15
158 > 20 13

Vehicle
speed
(km/h)
Dive
(mm)
Squat
(mm)
Steering
wh pos
(deg)
< 10 — — —
10–33 84 60 —
34–39 84 60 87
40–49 54 48 50
50–59 54 48 42
60–68 54 48 34
69–78 54 48 27.5
79–89 54 48 21
90–99 48 48 16.5

Vehicle
speed
(km/h)
Dive
(mm)
Squat
(mm)
Steering
wh pos
(deg)
100–109 48 48 13
110–119 48 42 13
120–129 48 42 11.5
130–139 42 42 11.5
140–149 42 42 10
150–158 42 36 10
159–179 42 36 6.5
179 > 36 36 5

Vehicle
speed
(km/h)
Pedal press rate
(steps/25 ms)
Normal Sport
< 14 2 1.3
15–49 3 2
50–99 4 2.6
100–134 5 3.3
135–199 6 4
199 > 7 4.6

Vehicle
speed
(km/h)
Pedal release rate
(steps/25 ms)
Normal Sport
< 19 10 6.6
20–78 5 3.3
79–168 6 4
168 > 7 4.6

lets the pressure inside the center sphere 1 move the control
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 somewhat
on tire size). It is located on the gearbox where the
speedometer cable attaches, or in some versions, on the cable
itself.

With the improved resolution of the vehicle speed sensor,
the rules formerly referencing to 30 km/h are changed to
24 km/h. Thus, the suspension switches to hard mode if the
brake pressure sensor detects a pressure above 30 bar
and a vehicle speed in excess of 24 km/h.
Similarly, the suspension will switch to soft mode if the
ignition switch is turned on, for a maximum of 30 seconds,
but reaching a vehicle speed of 24 km/h will cancel
this mode prematurely. It will switch to soft also if any door
or the tailgate is opened but the vehicle speed is below
24 km/h. The reason for this is to equalize the pressure between
all three spheres of an axle. Without it, the center
sphere would retain its former pressure and once the vehicle
exceeds the speed of 24 km/h, opening it would make
the car jump or drop, depending on the actual pressure.
It is important to note that the suspension will switch to
soft mode even with the ignition switch turned off. Should
the doors remain open with the ignition switch in the off position,
the suspension soft mode will be subjected to a 10-
minute timeout period to avoid draining the battery as the
soft mode requires the electric valves to be energized.