DIRAVI

DIRAVI is the name given by Citroën to its proprietary power steering system, first seen in 1970.

DIRAVI is an acronym for “Direction à rappel asservi” literally meaning "steering with controlled return" more accurately described in English as “power steering with power assisted return”.

This DIRAVI system[link] is an addition to the integrated Citroën hydropneumatic suspension and braking system and apart from its hydraulic power supply is independent of it.

This unique Citroën power operated self centering steering system is fitted to: Citroën SM, Citroën CX (most), Citroen XM (early Left Hand drive V6), Maserati Quattroporte II, Maserati Khamsin

Features

Fully hydraulic.
Power operated unlike conventional power assisted steering systems.
Automatic return to straight ahead position -whenever the engine is running the steering wheel will centralise, even when parked.
Artificial feel inbuilt - centering force varies in proportion to vehicle speed and/or steering wheel deflection.
Power for the system from a regulated high pressure hydraulic pump which also operates the brakes and suspension system.
The steering is operated by a rack and pinion system which normally only works as a feedback loop.
The rack takes the form of a double acting hydraulic ram, but is capable of taking over full steering function in the event of a hydraulic failure.
A hydraulic power safety prioritisation valve sets hydraulic fluid availability to each circuit in the Citroën system,
The steering is first to loose hydraulic power in a hydraulic system failure, whence it falls back to an inbuilt manual backup.

Advantages

Requires minimal physical exertion
Steering becomes an extension of thought process
Devotees find DIRAVI a delight to use.
Very fast – 2.0 turns lock to lock in SM configuration
Can be set up permitting vehicle to travel in a straight line without driver input on a constant camber road in still conditions.
Blowouts etc. cannot effect steering wheel or the direction of the steered wheel which can only be moved by steering wheel input.

Disadvantages

No feedback to the driver
Driver must survey visual cues to determine approach of roadholding limit
Requires familiarization - novices find DIRAVI too fast and sensitive

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