Petition Against the Ending of Citroën Hydropneumatics

Some die-hard Citroën fans are pretty miffed that the company has decided it is the end of an era for hydropneumatic suspension.  So much so that one owner has has sent a petition asking them to keep development alive and utilize it in future models.  We disagree with the tone of the petition and give our reasons below.  But first thing first.  Here is link to the original document:

For those of you who do not speak the Language of Angels, here is a rough translation:

Attention :
Mr. Denis Duchesne
Director PSA Excellence System

Petition against the ending of the PSA Citroën hydropneumatic system

With the creation by Citroën of the DS of 1955 (the petition creator has forgotten the 15CV H but his intentions are good so…), the hydropneumatic system revolutionized comfort, grip, ride and vehicle safety.  It was so obviously a superior system from the outset, compared to all competing cars’ suspension systems.  And with the addition of electronics, such as the C6, we achieved a quality never before seen in wheel/road surface communication.  And it is at this moment in history that the Directorate of PSA has
decided to end this wonderful invention that has made Citroën known worldwide and given the company its legendary reputation!  How can you erase 60 years of original art creation, which made Citroën “manufacturer of the century”?

At this point, can the demands of financial and stock requirements which are manifestations of the perversity of the economy, supplant human intelligence and genius?  How can you make such an unacceptable decision to regress given that the marque has surpassed the competition with its spectacular innovations in road safety? (According to insurance statistics, Citroën is the marque least involved in accidents).

It would be a shame if the leaders of PSA were to forget that Citroën is the only manufacturer who managed to give the various components of vehicles (suspension, braking, steering, lighting, etc.) intelligent cybernetic behaviour systems…

And how dare you leave in disarray all owners of Citroën hydropneumatic cars – from the DS 19 to the C6; cars which have marked the history of the automobile by their avant-garde qualities?   What will current Citroën owners do when they need to replace their current hydropneumatic vehicle, knowing that they no longer have the choice of metal springs of (an anachronism from the time of the ark)?  This is a betrayal; an insult to the innovative engineers and designers of this technology; and a denial of scientific

In addition, this decision is a strategic mistake, for, without this hydropneumatic system, Citroën models will lose their specific character and will just fall in line with their many competitors, becoming no different from all the others!  Many customers will leave the brand out of spite.  Why continue to buy Citroën since nothing fundamental will distinguish this manufacturer any longer!!

Do not erase this long and distinguished intellectual and industrial adventure of hydrotech and reconsider this absurd and desperate decision.  Personally take the time to study and objectively compare the qualities (especially ride comfort and handling) that Citroën models offer…   The hydropneumatic system must actually qualify for the best invention in automotive history and the fruit of genius and passion should not disappear!

Bernard Grand
MA Physical Sciences
Doctor of Philosophy

And our rebuttal:

Dear Mr. Duchesne,

We respectfully disagree with Mr. Grand’s petition to insist that Citroën carry on with hydropneumatic suspension in its cars.  We do, however, hope that the company has carefully considered ending its use.  Citroën has innovated for 50 years in the automotive industry with fluid based suspension technology, but the reality is that today’s electronically controlled active suspension systems perform better.  Not only can they vary shock absorber firmness to match changing road or dynamic conditions, some also use actuators to literally raise and lower the chassis independently at each wheel.  And they can do so in a faster response time.  We feel that Citroën should be applying the vast expertise it has in hydropneumatic suspension technology to developing a leading edge advanced electronically controlled active suspension or some new variation thereof.  And frankly there’s no time like the present to put full resources into that pursuit.

The fact is time and suspension technology in Citroën’s competitors have actively advanced.  Mercedes, BMW, and others offer electronically controlled active suspension.  They have partnered with component manufactures to advance the technology to the point where it offers not only a comparable (some claim superior) ride, but many conclude it is more cost effective to produce than Citroën’s hydropneumatic system?   We would point out however that electronically controlled suspension systems become extremely costly when, in time, they must be replaced.  We hope Citroën has factored in not only the cost of utilizing this technology in manufacturing competitively priced vehicles, but also what customers will experience in long term reliability and service expense.  From what we can ascertain, (based on the cost of a Mercedes active suspension strut assembly replacement which does have a limited life span), a Citroen hydraulic-based suspension system is a more cost effective alternative.  And we Citroën devotees can attest to its ride and handling attributes.  This is why there is such a concern and we trust that the company has not lost sight of innovative engineering being a cornerstone to its future success.

What Citroën developed over the years has been a remarkable achievement.  However the superiority of a Citroën DS over very other automobile of the era was due only in part to its hydraulic suspension.  We would like to encourage the company to offer vehicles with the ergonomic and other engineering advantages that the DS is still recognized for today;  Unobstructed views or the road, phenomenal interior room, inboard mounted front disc brakes and body panels that can be easily changed if need be.   These are but a few of the hundreds of innovations Citroën could choose to offer in a new generation of DS not based on a few badges and marketing hype, but a true lineage to the original DS.   Offering this along with electronic controlled active suspension (possibly with a hydraulic lineage and certainly with driver controllable ride height) would in our opinion actually make it even a better car,   Introduce a design with a strong homage to the original DS and you would have a vehicle that would entice the new buyers and old!

As to Mr. Grand’s statement that according to insurance statistics, Citroën is the marque least involved in accidents, we would like to point that while Citroën’s safety record on the road is commendable, it would be truly impressive if Citroën were the top selling marque.

Where we wholeheartedly agree is with Mr. Grand’s suggestion that Citroën take the time to study and objectively compare the qualities (especially ride comfort and handling) that classic Citroën models offer.  Don’t loose sight of that and ensure that new models can be held to those benchmarks at a minimum.  Then brand “Innovative Technology” that the company has been touting not just as a market slogan, but as proof these objectives have been met!

If Citroën is to be successful going forward, the company needs to tie-in control of the suspension, braking, steering, lighting, etc. better than anyone.  Mr. Grand refers to this as intelligent cybernetic behaviour systems.   Interesting phrase and one we’d like to tweak somewhat in the hope that it becomes a new corporate mantra at Citroën:  Deliver to customers a superlative cybernetic automotive experience.

George Dyke & John McCulloch
Co editors

(remember us in North America!)




Update Footnote:

From: Julian Marsh, Tuesday, January 21, 2014

Yesterday, a friend contacted Citroën UK to express concern about the dropping of hydropneumatics and was told there are no plans to do so and that both the C5 and C4 Grand Picasso are still available with the system.  C4 Grand Picasso?  It has pneumatic rear suspension.  So they don¹t even understand what the word ‘hydropneumatic’ means.

1 comment

  1. To the writer:
    What do you think the Citroen XM suspension system is?
    Mk1 XM have a Hydra-active suspension with an added electro valve, that is mounted in the front lower centre, mounted on it is a 70Bar accumulator sphere, this in turn feeds another passive valve at the rear centre, which in turn allows the centre mounted accumulator sphere to supply the rear suspension extra softness when the driver is smooth sailing, otherwise when the driver input controls detect any cornering or swift driving it, the various sensors detect a change in the way the car is driven, this in turn tells the hydractive computer to take action, the action it takes will depend on its programmed algorythm , this in turn switches off the valve via its solenoid that is controlled by the electronic computer, there are 7 sensors on the car, one in the steering column, one on the body/chassis, one on the brake pedal, I have a full schematic and other write up, including the latest software.
    The Mk2 XM is a more advanced system, it have two electro valves, the computer have pressure switches, the computer receives much more up to date information and it in turn can adjust the suspension independently at each wheel, unfortunately neither Citroen nor a competent mechanic have been able to diagnose , trouble shoot and rectify the variations of this very complex computer and a variety of pressure switches, hence the vast majority of the MK2 XM owners who have got tired of harsh suspension, they have installed whats known as a permanent Comfort Sphers on all 4 corners, the ride is therefore , unfortnately not controlled by the computer, but rather it becomes a Hydropneumactive without the control signal from the computer to activate or deactivate it(since if it have had a problem to begin with, then 100% the control signals for both the electrovalve is missing in any case, so the issue is null and void).
    The C5 and the C6 uses even more complex data to control the suspension, it can use satellite for its feed of the roads ahead, this in turn would control the Activa computer this in turn would feed a variety of feeds to each wheel , it is way more complex, still using the spheres.
    If any of you folks want to know more about any of these systems, I can tell you.

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