High-Pressure Hydraulics by Citro?n

[jeanlouis]

Like for the most current cars sold in France, the magazine l'Auto-Journal tested one of the first CX 2000 on 50000 kms and published their results at the end of 1975. The car is entirely dismantled after the endurance test and all the parts are examined.







For it first production year the CX was not still available with assisted steering. Hydraulics is simplified : HP pump monopiston directly driven by the camshaft and simple steering rack.
The journalist painted components in black for the photo, I presume. Normally it is in green.

 

[jeanlouis]

I don't know if they liked especially Citroën GS at l'Auto-Journal, but the endurance of this amazing car was tested two times : in 1971, the first model 1015 cm3 and two years later, the new 1220 cm3 version.





I remember, stopping, mine too went downstairs front first, I don't know why...kinky look!

 

[jeanlouis]

L'Automobile also realized some endurance trials, on the same way than his competitor l'Auto-Journal. The distance was "only" 40000 kms and cars were not dismantled at the end of the test.




A GS 1220 in the basic version, first model 1973

 

[jeanlouis]

Until where with a CX 2500D Pallas 5 gears full tank ?
To answer to this question the magazine l'Automobile made this experience by a winter day in 1979.


Departure from Lille at 10:00 PM to southern by the highway.





The journalist chose to travel by night (lower traffic) and by dry weather (better rolling) to reduce the fuel consumption
Tank contain = 68 liters
Average speed = 100 km/h (105 at the meter)
Travel time = 10 hours
Running out of gas after 1050 kms then a consumption : 6.2 liter/100 km, 1/3 less than the same model working with gasoline !

 

[dargelos]

Impressive mileage for a luxury car. 100kpm/h is 62 mph, the optimum crusing speed for fuel saving is usualy quoted as 56 mph, but that is for average cars. The CX has the advantage of a particularly efficient aerodynamic shape so it's optimum speed is going to be a little faster. Not many drivers will do so well in real life, they want to go as fast as possible and get bored maintaining a constant unvarying velocity.
It's not just about saving money, the engine is also less polluting. Diesel has a bad reputation at the moment, deserved in the case of stop start urban driving, but on the open road, away from the town, it is producing less CO2 than petrol for long distance cruising.

 

[jeanlouis]

Thank you very much Dargelos for your comments about cars consumption, it gave me the idea to compare Citroen CX with Citroen C6. I know it is not reasonable, there is about 30 years difference between the two cars. I did it only because it is two highway vehicles with the same profil.
The C6 was a marketing failure, it is no more assembled for already several years.



The C6 is certainly more pleasant to drive but this difference has a cost :
- a big frontal area that reduce the aerodynamic gains
- 500 kg on the scales, a C6 empty is the equivalent of a CX full loaded !

 

[jeanlouis]

I remember, it was yesterday...


It was on the parking in the early eighties : my blue DS 20 (model 1970) in left parked beside those of my neighbors, DS 23 injection Pallas 73 and a tired DS 21 Pallas 68. At this age this Citroën was still current in the streets.


I stacked production graphs of Traction, DS and CX. As you can see, at the opposite of the CX, Traction and DS kept some good sales nearly until the end of their production. It explain why these two cars (like 2CV for example) stayed in the streets set a very long time and the place they have in people mind, in France at least.

 

[jeanlouis]

The ID/DS range from 1957 to 1974



I made the list of the different ID/DS models with prices and supplements compared with the basic model. The difference of price between ID and DS increase with years and the multiple perfectings brought on hydraulics systems of the DS. In 1970 a DS 20 is 30% more expensive than a D Special.


May 1970
L'Automobile is testing the most popular DS models : 5 saloons, 2 estates.
No Pallas, Prestige or Convertible !




D Special that replace ID 19 is the new basic model of the range

Starting the DS 21 in 1965, the range is growing more and more.
The bigger engine 2.1 liter or 2.3 liter is not too expensive, less than Pallas finition or Electronic Injection. Each customer could find a model at his taste or according his need. The DS 20 is just at the middle of the range.

 

[jeanlouis]

Travelling, travelling and travelling again, hydraulics Citroën were designed for it. These photos were shoted from the trunk of the previous car. It was the special feature of Andre Martin, the favorite photographer of the constructor at this time.

 

[jeanlouis]

Some GS and CX comparative tests

 

[jeanlouis]

Citroën 1934-1988


Happy new year to everybody !

 

[jeanlouis]

The main difference between Traction and DS 21 Injection Electronic hydraulic gearbox

Imagine, you are in 1970 at Citroën Reims in France, a brand new DS21 Pallas Injection is waiting for it first owner.

Delivery of the keys by the boss of the cars dealership

A strange and unknown car behind

The finition is in progress at Citroën!

If money was not so expensive, I should buy one like it







Ready for the road



OK, you are right, this Citroën has been entirely rebuilt

A second DS was used as organs bank
I found these photos on the web. Still today there is some courageous Citroënists for restoring these outstanding cars. Happily! Who could guess this DS is fifty?

 

[dargelos]

Those seats are a fabulous shade of rose, they remind me of Salvador Dali's Mae West Lips. That must have been a daring choice of colour for the time, but they are in keeping with the elegant sensuality of the car as a whole. If the Italian two seaters like Ferrari are thought of as sex on four wheels, a beautiful DS like the one above is making love on four wheels

 

[jeanlouis]

In 1994, for the 40th anniversary of the hydropneumatic suspension, Citroën presented Xantia Activa equiped with a new anti-rolling device named SC CAR (Système Citroën Contrôle Actif du Roulis).



Production of models with hydropneumatic suspension until 1994

PxV = constant. From the 15/6 H to Xantia Activa, hydropneumatic is working according the law of Mariotte (see the first post of this thread)

Paul Magès, who created most of hydraulic devices on the DS, had imagined an anti-rolling suspension entirely hydraulic on the same principle than the height control, a kind of transversal control. Too expensive, with too slow reactions, this system was left. Hydraulics had not the short response times of actual electronic. For the assisted steering, he had already invented in 1960 the assistance according the speed of the vehicle (with a centrifugal regulator), a device that we shall find ten years later on the SM.

1987 : With the BX GTI 16 valves, the limits of a basic hydropneumatic suspension are reached. For a sport car, a classic system seem more efficient and even more comfortable! 160 ch, 220 km/h and 1100 Kg only, big anti-rolling bars and increased gas pressure in the spheres are necessary. It was before the XM and hydractive suspension.

1994 : the new Xantia Activa

SC CAR is an additonal device totally independant of Hydractive suspension.
2 jacks (front left and rear right) are able to keep straight the car in curve.
A specific sphere, assembled to make the suspension more flexible in straight, is disconnected when the calculator ask it.


Front jack : Like a jack of assisted steering, high pressure on the small piston section, modulated pressure on the large one.

Rear jack

Additional sphere

 

[jeanlouis]

A Xantia version for each customer


We can see the difference in curve between "classic" hydropneumatic suspension and Activa.
Personally I think that the best is the ennemy of the good.
Indeed for passengers it is more pleasant to travel in a car that is not rolling in curve. As driver, I am not embarrassed with it. I ear that owners of Activa consumed more tyres than others because mechanicaly they travelled faster in curve. It is possible. Some journalist found the suspension firmer than the one of a simple Hydractive II Xantia. Anyway Citroën has never assembled SC CAR on another car. :thinking:

 

[jeanlouis]

How is working an hydractive suspension of XM or Xantia ? (at least those that remain in the traffic )


Left : a Xantia without Hydractive
Right : a XM with Hydractive
This suspension is not really active like SC CAR of Xantia Activa that modulate it reactions in curve according the speed of the vehicle.
We have only two states : firm on 4 spheres or soft on 6 spheres. One of these states is selected in 2/100 seconde by the calculator. In more, according his taste, the driver can choose the mode "automatic" or "sport" from the habitacle.





Like any hydropneumatic Citroën starting the DS, the pressure in rear suspension spheres is also used for rear brakes.

The only way to recognize a Xantia or XM with hydractive is to watch between the front seats. There is an additional suspension control (sport or automatic mode) in more of the traditional height control.

 

[jeanlouis]

Spring 1989 : Citroën present the new XM with its amazing hydractive suspension






From the luxurious first catalog :


I remember, the financial director of the company where I worked at this age bought one exactly like the model of the catalog : V6, dark grau, black leather interior. It was the first XM I saw.

The mastered road was the slogan of the constructor







Leather interior, alliage wheels, air conditioning were only in option



At last a V6 on an upperscale Citroën

This useful side of the XM is not appreciated by everybody !

At the beginning, in May 89, it was only 2 available models.
Carburator and Diesel versions in autumn, V6 - 24 valves in 90, estate in 91.

 

[jeanlouis]

Interesting collection, I found the first number at the news storekeeper : a beautiful 2CV France 3 for only 6.99 euros :thumbs up:
I noticed some original models : SM Opera by Chapron, Mehari 4x4, ID19 estate ...

Already 15 models scale 1/24 created today.
I bought 11 but I quickly stopped my subscription after 7 numbers. Now I am buying only when the model is interesting me.
Below 3 Citroën that represent 3 generations of hydropneumatics.





Three ages but three cars with barely the same dimensions except the height. I could add also the same comfort at the rear places.

 

[jeanlouis]

About the list of my last post, I added a line for the price and now I am afraid it is creating a confusion in your mind. We have to distinguish technology development from prices development :

- DS19 1958 : 11.097 F (1.109.700 old Francs) - 140 km/h
- DS21 IE 1970 : 22.180 F - 184 km/h
- CX Prestige auto 1981 : 95.100 F - 185 km/h
- CX Prestige auto 1989 (the last) : 191.000 F - 195 km/h
Without comment !

 

[jeanlouis]

Presented at Geneve Motorshow in mars 70, the SM with V6 Maserati engine is fifty.
First official outdoors photos are shoted, a catalog is also available but people has to wait the autumn for driving or ordering one.
Price : 46000 Francs, around 2 times the price of a DS 21 Pallas injection.
Journalists and first customers are surprised by a very direct power steering with powered return (2 wheel turns from lock to lock).
Still a Citroën that don't let indifferent!