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DS19 Series I
The Citroën DS is a four-door, front-engine, front-wheel-drive mid-size car manufactured and marketed by the French company Citroën from 1955 to 1975 in sedan, wagon/estate and convertible body configurations. Italian sculptor and industrial designer Flaminio Bertoni and the French aeronautical engineer André Lefèbvre styled and engineered the car. Paul Magès developed the hydro pneumatic self-levelling suspension.
Noted for its aerodynamic, futuristic body design and innovative technology, the DS set new standards in ride quality, handling, and braking. Citroën sold 1,455,746 cars, including 1,330,755 built at the manufacturer's original mass-production plant in Paris at the Quai André-Citroën (previously the Quai de Javel).
The DS came third in the 1999 Car of the Century poll recognizing the world's most influential auto designs and was named the most beautiful car of all time by Classic & Sports Car magazine.
After 18 years of secret development as the successor to the Traction Avant, the DS 19 was introduced on 5 October 1955 at the Paris Motor Show. In the first 15 minutes of the show, 743 orders were taken, and orders for the first day totalled 12,000.
The ID19 followed the DS19's example in using a punning name. While "DS" is pronounced in French as "Déesse" (goddess), "ID" is pronounced as "Idée" (idea).
The DS was the first mass production car with front power disc brakes. It also featured hydro pneumatic suspension including an automatic leveling system and variable ground clearance, power steering and a semi-automatic transmission (the transmission required no clutch pedal, but gears still had to be shifted by hand), though the shift lever controlled a powered hydraulic shift mechanism in place of a mechanical linkage, and a fiberglass roof which lowered the center of gravity and so reduced weight transfer. Inboard front brakes (as well as independent suspension) reduced unsprang weight. Different front and rear track widths and tire sizes reduced the unequal tire loading, which is well known to promote understeer, typical of front-engined and front-wheel drive cars.
As with all French cars, the DS design was affected by the tax horsepower system, which effectively mandated very small engines. Unlike the Traction Avant predecessor, there was no top-of-range model with a powerful six-cylinder engine. Citroën had planned an air-cooled flat-6 engine for the car, but did not have the funds to put the prototype engine into production.
In the DS they were also used for the suspension, clutch and transmission, although the later ID19 did have manual steering and a simplified power-braking system.
At a time when few passenger vehicles had independent suspension on all wheels, the application of the hydraulic system to the car's suspension system to provide a self-levelling system was an innovative move. This suspension allowed the car to achieve sharp handling combined with very high ride quality, frequently compared to a "magic carpet". The hydro pneumatic suspension used was pioneered the year before, on the rear of another car from Citroën, the top of range Traction Avant 15CV-H.allum, Roy Axe, Paul Bracq, and Leonardo Fioravanti.
The 1955 DS19 was significantly more expensive than the car it replaced, the Citroën Traction Avant. This did impact potential sales in a country still recovering economically from World War II, so a cheaper submodel, the Citroën ID, was introduced in 1957. The ID shared the DS's body but was less powerful and luxurious. Although it shared the engine capacity of the DS engine (at this stage 1,911 cc), the ID provided a maximum power output of only 69 hp compared to the 75 hp claimed for the DS19. Power outputs were further differentiated in 1961 when the DS19 acquired a Weber-32 twin bodied carburetter, and the increasing availability of higher octane fuel enabled the manufacturer to increase the compression ratio from 7.5:1 to 8.5:1. A new DS19 now came with a promised 83 hp of power. The ID19 was also more traditional mechanically: it had no power steering and had conventional transmission and clutch instead of the DS's hydraulically controlled set-up. Initially the basic ID19 was sold on the French market with a price saving of more than 25% against the DS, although the differential was reduced at the end of 1961 when the manufacturer quietly withdrew the entry level ID19 "Normale" from sale. A station wagon variant, the ID Break, was introduced in 1958.
In a hydro pneumatic suspension system, each wheel is connected, not to a spring, but to a hydraulic suspension unit consisting of a hydraulic accumulator sphere of about 12 cm in diameter containing pressurized nitrogen, a cylinder containing hydraulic fluid screwed to the suspension sphere, a piston inside the cylinder connected by levers to the suspension itself, and a damper valve between the piston and the sphere. A membrane in the sphere prevented the nitrogen from escaping. The motion of the wheels translated to a motion of the piston, which acted on the oil in the nitrogen cushion and provided the spring effect. The damper valve took place of the shock absorber in conventional suspensions. The hydraulic cylinder was fed with hydraulic fluid from the main pressure reservoir via a height corrector, a valve controlled by the mid-position of the anti-roll bar connected to the axle. If the suspension was too low, the height corrector introduced high-pressure fluid; if it was too high, it released fluid back to the fluid reservoir. In this manner, a constant ride height was maintained. A control in the cabin allowed the driver to select one of five heights: normal riding height, two slightly higher riding heights for poor terrain, and two extreme positions for changing wheels. (The correct term, oleo pneumatic (oil-air), has never gained widespread use. Hydro pneumatic (water-air) continues to be preferred overwhelmingly.)
The DS did not have a jack for lifting the car off the ground. Instead, the hydraulic system enabled wheel changes with the aid of a simple adjustable stand. To change a flat tyre, one would adjust the suspension to its topmost setting, insert the stand into a special peg near the flat tyre, then readjust the suspension to its lowermost setting. The flat tyre would then retract upwards and hover above ground, ready to be changed. This system, used on the SM also, was superseded on the CX by a screw jack that, after the suspension was raised to the high position, lifted the tire clear of the ground. The DS system, while impressive to use, sometimes dropped the car quite suddenly, especially if the stand was not placed precisely or the ground was soft or unleveled.
The central part of the hydraulic system was the high pressure pump, which maintained a pressure of between 130 and 150 bar in two accumulators. These accumulators were very similar in construction to the suspension spheres. One was dedicated to the front brakes, and the other ran the other hydraulic systems. (On the simpler ID models, the front brakes operated from the main accumulator.) Thus in case of a hydraulic failure, the first indication would be that the steering became heavy, followed by the gearbox not working; only later would the brakes fail.
Two different hydraulic pumps were used. The DS used a seven-cylinder axial piston pump driven off two belts and delivering 175 bar (2,540 psi) of pressure. The ID19, with its simpler hydraulic system, had a single-cylinder pump driven by an eccentric on the camshaft.
The DS was initially offered only with the "hydraulique" four-speed semi-automatic (bvh—"boîte de vitesses hydraulique") gearbox.
This was a four-speed gearbox and clutch, operated by a hydraulic controller. To change gears, the driver flicked a lever behind the steering wheel to the next position and eased-up on the accelerator pedal. The hydraulic controller disengaged the clutch, engaged the nominated gear, and re-engaged the clutch. The speed of engagement of the clutch was controlled by a centrifugal regulator sensing engine rpm and driven off the camshaft by a belt, the position of the butterfly valve in the carburettor (i.e., the position of the accelerator), and the brake circuit. When the brake was pressed, the engine idle speed dropped to an rpm below the clutch engagement speed, thus preventing friction while stopped in gear at traffic lights. When the brake was released, the idle speed increased to the clutch dragging speed. The car would then creep forward much like automatic transmission cars. This drop in idle throttle position also caused the car to have more engine drag when the brakes were applied even before the car slowed to the idle speed in gear, preventing the engine from pulling against the brakes.
Manual - 4 speed and 5 speed
The later and simpler ID19 had the same gearbox and clutch, manually operated. This configuration was offered as a cheaper option for the DS in 1963. The mechanical aspects of the gearbox and clutch were completely conventional and the same elements were used in the ID 19. In September 1970, Citroën introduced a five-speed manual gearbox, in addition to the original four-speed unit.
In September 1970 Citroën introduced a 3-speed fully automatic Borg-Warner gearbox. The full-automatic transmissions were intended for the US market, but Citroën withdrew the DS from the US in 1972, so most automatic DSs, fuel-injected DS 23 sedans with air conditioning, were sold in Australia.
The DS was originally designed around an air-cooled flat-six based on the design of the 2-cylinder engine of the 2CV, similar to the motor in the Porsche 911. Technical and monetary issues forced this idea to be scrapped.
Thus, for such a modern car, the engine of the original DS 19 was also old-fashioned. It was derived from the engine of the 11CV Traction Avant (models 11B and 11C). It was an OHV four-cylinder engine with three main bearings and wet liners, and a bore of 78 mm (3.1 in) and a stroke of 100 mm (3.9 in), giving a volumetric displacement of 1911 cc. The cylinder head had been reworked; the 11C had a reverse-flow cast iron cylinder head and generated 60 hp (45 kW) at 3800 rpm; by contrast, the DS 19 had an aluminum cross-flow head with hemispherical combustion chambers and generated 75 hp (56 kW) at 4500 rpm. Apart from these details, there was very little difference between the engines: even the locations of the cylinder head studs were the same, so that it was possible to put the cylinder head of a DS on a Traction Avant engine and run it.
Like the Traction Avant, the DS had the gearbox mounted in front of the engine, with the differential in between. Thus some consider the DS to be a mid engine front-wheel drive car.
The DS and ID power plants evolved throughout its 20-year production life. The car was underpowered and faced constant mechanical changes to boost the performance of the four-cylinder engine. The initial 1911 cc three main bearing engine (carried forward from the Traction Avant) of the DS 19 was replaced in 1965 with the 1985 cc five-bearing wet-cylinder motor, becoming the DS 19a (called DS 20 from September 1969).
The DS 21 was also introduced for model year 1965. This was a 2175 cc, five main bearing engine; power was 109 hp This engine received a substantial increase in power with the introduction of Bosch electronic fuel injection for 1970, making the DS one of the first mass-market cars to use electronic fuel injection. Power of the carbureted version also increased slightly at the same time, owing to the employment of larger inlet valves.
Lastly, 1973 saw the introduction of the 2347 cc engine of the DS 23 in both carbureted and fuel-injected forms. The DS 23 with electronic fuel injection was the most powerful production model, producing 141 hp (105 kW).
IDs and their variants went through a similar evolution, generally lagging the DS by about one year. ID saloon models never received the DS 23 engine or fuel injection, although the Break/Familiale versions received the carburetted version of the DS 23 engine when it was introduced, supplemented the DS20 Break/Familiale.
The top of the range ID model, The DSuper5 (DP) gained the DS21 engine (the only model that this engine was retained in) for the 1973 model year and it was mated to a five-speed gearbox. This should not be confused with the 1985 cc DSuper fitted with an optional "low ratio" five-speed gearbox, or with the previous DS21M (DJ) five-speed.
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