Hydraulics Quiz No. 4 (second copy) — Hydractive I and II suspension

In this document

Presentation and instructions

This document is the fourth of six "Hydraulics Quizzes" from a correspondence course. The questionnaire must be "returned no later than fifteen days after receipt" p. 34, and invites the trainee to time their completion. A Parisian telephone and fax number (prefix "16 1" for the provinces) are provided in case of difficulty p. 34.

Questions on Hydractive suspension (Q1 to Q12)

The first twelve questions concern the principles of the suspension: link between flexibility and load, role of the nitrogen volume in the spheres (Q2), "firm" and "soft" settings (Q3, Q7, Q9), function of the solenoid valve as an interface between the electronic computer and various components (Q4), composition of a Hydractive system — stiffness regulator, additional sphere, height corrector (Q5) — and operation of the stiffness regulator (Q6, Q7).

Two questions precisely distinguish the generations of the system: Hydractive I is associated with XM vehicles and a manufacturing date "from 1.02.1993" or "before 1.02.1993" depending on the items proposed (Q10), as is the case for Hydractive II on XM and Xantia (Q11). Question 12 details the operation of a "ball valve" according to the firm or soft mode and the direction of pressure variation p. 34.

Identification exercise (Q13)

Page 35 proposes a hydraulic suspension and braking circuit diagram, seen in plan, with the rear of the vehicle on the left and the front on the right. Eleven numbered markers must be associated with a list of eleven components: stiffness regulator (front/rear), height corrector (front/rear), suspension block (front/rear), priority valve, brake metering valve, brake sensor, solenoid valve (front/rear). Four combinations of answers (13a to 13d) are proposed in table form p. 35.

The page ends with a space for free remarks and a box to fill in (study time, signature, place, date), with the instruction "Keep the carbon copy" p. 35.

Context

Historically, the Hydractive suspension, introduced by Citroën in the early 1990s, combines the hydropneumatic principle invented by Paul Magès with electronic management of firmness ("firm" or "soft" mode) controlled by a computer. The first generation (Hydractive I) equips the XM, the second (Hydractive II), more advanced, appears with the Xantia Activa and then on the XM. These technical developments were initiated after the retirement of Paul Magès, who left Citroën in September 1974 after a 49-year career (photographs of the retirement; letter from Mr. Meignan), and nevertheless directly extend the research he had conducted on the gas sphere and stiffness regulation, the first plans for which date back to 17 February 1944 (plans for hydropneumatic suspension).

Archivist's perspective

This document illustrates how Citroën transmitted, in the 1990s, a fine understanding of its hydraulic systems to its own technical staff — probably dealers or after-sales personnel — via training structured into six modules.

The fact that this same quiz exists as a "second copy" suggests distribution to several trainees or the preservation of several versions of the same educational material. The identification exercise p. 35 testifies to the concern to have the components of the circuit handled concretely, beyond the mere theory of multiple-choice questions.

This quiz is part of a series consistent with Hydraulics Quiz No. 5 on DIRASS and DIRAVI, and Quiz No. 6, confirming the existence of a complete continuing education programme around the technical legacy of Paul Magès, long after his own time at Citroën — he having retired to Ramatuelle (Var) where he became a municipal councillor in 1977 (list of municipal council members), until his death on 22 September 1999.