RE: AD V7 #127 - 164 auto suspension

["Rajko Sabo, Slovenia" <RAJKO@xxxxxxxxxxxxx>]

In Alfa Digest V7 #127 Simon Rodda asked:

>Can someone describe how the 164Q's electronic controlled suspension works?

Here is some theory...(Taken from the "164 Cloverleaf Owner's Manual")

The Alfa Romeo controlled damping suspension electronic system is
capable of instantly varying shock-absorber adjustment on all four
wheels, ensuring the best car performance at all times in terms of
comfort, road holding and driving safety.

Suspension characteristics determining the car's behaviour in
various circumstances, are ELASTICITY (when the suspension absorbs
the strain) and DAMPING (when the suspension returns to its normal
position).

System elasticity is guaranteed by the springs coaxially positioned
to the shock-absorbers, which operate during the return phase thus
causing elasticity damping.

In vehicles equipepd with traditional suspensions (i.e. non-
adjustable) the type of damping action performed determines the
vehicle's reactions: a "soft" damping action privileges driving
comfort, whilst a "hard" setting (high damping action) results
in better road holding. Suspension adjustment can therefore in
most cases only be a compromise between sufficiently safe road
holding and adequate comfort. In any case, once suspension
characteristics have been established (remaining non-adjustable)
their behaviour remains constant independently of the type of
driving or speed adopted, and of the variations in load when
taking bends, braking and all other variable driving parameters.

Thanks to the electronic processing of signals sent by various
sensors to the ECU, the Alfa Romeo controlled damping suspension
system is capable of recognising all the above conditions, and
of consequently varying shock-absorber adjustment so as to ensure
an adequate reaction to strain.

The controlled damping suspensions can operate according to two
intervention logics, which the driver selects by simply pressing
one of the two push-buttons located on the central console over
the climatization controls:
- - "AUTO" mode,
- - "SPORT" mode.

These intervention logics act on the two adjustment possible on
each shock-absorber: soft or hard setting. The change-over from
soft to hard setting (and vice versa) is carried out by a
solenoid valve, fitted onto each shock-absorber, in approximately
5 milliseconds.

"AUTO" logic operation

When the "AUTO" function is actuated, the electronic control unit
changes shock-absorber setting instantly in relation to the
information sent by the six sensors relative to different driving
conditions.

The sensors installed are the following:
- - vertical acceleration sensor, located on the electronic control
  unit body, which registers all car body oscillations in a
  vertical direction;
- - steering angle and steering wheel rotation speed sensor, fitted
  into the steering column support, which registers the radius of
  the bend being taken and the speed at which the steering wheel
  has attained said angle, so as to identify a sporty or moderate
  driving style, or emergency actions such as sudden steering;
- - braking sensor, fitted on the brake pump, which registers all
  circuit pressures exceeding 20 bar,
- - tachometric sensor, positioned on the gearbox, which registers
  vehicle momentary speed;
- - engine throttle opening sensor located on the throttle body,
  which signals an opening angle in excess of that pre-established
  when in 1st or 2nd gear;
- - gearbox sensor which signals 1st or 2nd gear engagement.

"SPORT" logic operation

When the "SPORT" logic is selected, shock-absorber adjustment is
ALWAYS set to hard for a sporty driving style and the best road
holding possible.

At some other occasion when I have more time I'll write my
experience and remarks on the subject.

Rajko Sabo
Ljubljana, Slovenia 
'91 164 QV Zender
'81 Renault 18 TL
e-mail: rajko.sabo@domain.elided
Web page including my AR page:
www.geocities.com/MotorCity/Downs/2350

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