Citroën SM

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Citroën SM
Citroen SM Mulhouse FRA 001.JPG
Overview
Manufacturer Citroën
Production 1970-1975
Designer Robert Opron
Body and chassis
Class Grand tourer
Body style 3-door liftback
Layout MF layout
Related Citroën DS
Maserati Merak
Maserati Quattroporte II
Citroën CX
Powertrain
Engine 2.7 L V6
3.0 L V6
Transmission 5-speed manual
3-speed automatic
Dimensions
Wheelbase 290 cm (110 in)
Length 489.3 cm (192.6 in)[1]
Width 183.6 cm (72.3 in)
Height 132.4 cm (52.1 in)
Curb weight 1,460 kg (3,220 lb)
(carburetted version)
1,520 kg (3,350 lb)
(fuel-injection version)
Rear view - suspension in low position

The Citroën SM is a high-performance coupé produced by the French manufacturer Citroën from 1970 to 1975. The SM placed third in the 1971 European Car of the Year contest, trailing its stablemate Citroën GS, and won the 1972 Motor Trend Car of the Year award in the U.S. in 1972.

History[edit]

In 1961, Citroën began work on 'Project S' — a sports variant of the revolutionary Citroën DS. As was customary for the firm, many running concept vehicles were developed, increasingly complex and upmarket from the DS. Citroën purchased Maserati in 1968 with the intention of harnessing Maserati's high-performance engine technology to produce a true Gran Turismo car, combining the sophisticated Citroën suspension with a Maserati V6.[2]

The result was the Citroën SM, first shown at the Geneva Motor Show in March 1970. It went on sale in France in September of that year. Factory produced cars were all left-hand-drive, although RHD conversions were done in the UK and Australia.

The origin of the model name 'SM' is not clear. The 'S' may derive from the Project 'S' designation, the aim of which was to produce what is essentially a sports variant of the Citroën DS, and the 'M' perhaps refers to Maserati, hence SM is often assumed to stand for "Systeme Maserati"or"Sports Maserati". Another common alternative is Série Maserati,[3][4] but others have suggested it is short for 'Sa Majesté' (Her Majesty in French), which aligns with the common DS model's nickname 'La déesse' (The Goddess).

The SM was Citroën's flagship vehicle, competing with other high-performance GTs of the time from manufacturers such as Jaguar, Lotus, Ferrari, Aston Martin, Alfa Romeo and Porsche. It was also Citroën's way of demonstrating just how much power and performance could be accommodated in a front-wheel drive design.

Because the SM had a small 170 hp (130 kW) engine, the 0–100 km/h (0-60 mph) acceleration of 8.9 seconds[5] was adequate rather than exemplary - some competitors were quicker - the 288 hp (215 kW) Jensen Interceptor needed 6.4 seconds,[6] the 200 hp (150 kW) BMW 3.0CSi needed 7.5 seconds,[7] and the 200 hp (150 kW) Mercedes-Benz 350 SLC took 9.0 seconds.[8] Some owners have fitted the similar sized 220 hp (160 kW) Maserati Merak SS engine, which does improve the driving experience considerably.[9]

The SM introduced a new type of variable assist power steering that has since spread throughout the vehicle population.[10] DIRAVI as it was called, allowed great assistance to the motorist while parking, but little assistance at motorway speeds. If the driver released the steering wheel, then the steering would center back to the straight ahead position. It was geared for minimal steering input - with 2 turns from lock to lock, often described as like a go kart. This steering was controversial at the time - exaggerated strong-arm steering inputs needed on other 1970's cars could cause abrupt maneuvers in the SM.[11] When the SM was cast as a TV series regular on 1972's The Protectors, the lead actress refused to drive it because of the familiarization required from the steering.[12]

Contemporary automotive journalists were most effusive about the SM's dynamic qualities, which were unlike anything they had experienced before.[11] The SM provided a combination of comfort, sharp handling, and braking not available in any other car at the time. The magazine Popular Science noted that the SM had the shortest stopping distance of any car they had tested.[13]

Unfortunately, the SM did not find a sufficient customer base in the European GT market, but much of the SM's technology was carried forward to the successful Citroën CX, launched in 1974 the DIRAVI steering being the most obvious example. The same basic engine in enlarged 3.0 L form (some in Italy had 2.0 L) was used in Maserati's own Merak which, together with Maserati's Khamsin and Bora, used Citroën's high-pressure hydraulics for some functions, and the Citroën gearbox in the Merak, during the Citroën-Maserati alliance.

Styling[edit]

The SM in profile.

Designed in-house by Citroën's chief designer Robert Opron, the SM bears a vague family resemblance to the DS, especially in retaining the latter's rear-wheel spats. Seen from above, the SM resembles a teardrop, with a wide front track tapering to a narrower rear track.

The SM was unusually aerodynamic for its era, with Kamm tail and low drag coefficient of 0.26.[14] The ventilation intake is located in a "neutral" area on the hood, which makes the ventilator fan regulate the interior ventilation at all road speeds. European critics marveled at the resulting ability to travel for hours at 200 km/h (120 mph) in comfort and with impressive fuel economy on the large 90 l (20 US gal, 17 Imp. gal.) fuel tank.

The SM interior

With its distinctly modernist influence, the interior styling of the SM is as dramatic as the exterior. The small oval steering wheel is matched by oval gauges. The manual shift lever 'boot' is a highly stylized chrome gate. The seats are highly adjustable buckets with centre padding composed of many individual 'rolls'. High-quality materials are used throughout. The bonnet is aircraft grade aluminum, while the external bright work is stainless steel, rather than ‘cheaper’ chrome (except for "plastichrome" "SM" trim at the rear base of the rain gutter).

In 1970, it was a car of the future and the fastest front-wheel-drive car, with a factory-quoted top speed of 220 km/h (140 mph), and independent tests achieving as much as 235 km/h (146 mph). It was an example of the car as a symbol of optimism and progressive technology, similar to the SM's contemporary, the Concorde aircraft.[citation needed]

The SM's design placed eleventh on Automobile Magazine '​s 2005 "100 Coolest Cars" listing.

Technical innovations[edit]

The SM combines many unusual and innovative features, some of which are only just becoming commonplace on cars of today.[10] It borrows heavily from the innovations introduced on the DS, by including hydro-pneumatic (oleopneumatic) self-leveling suspension, and self-leveling lights that swiveled with the steering (except in the USA where these were illegal at the time).

The steering is self-centering and fully powered (as opposed to hydraulically assisted). This feature allows the front wheels to run near-zero caster, and means that there is no camber change as lock is applied, and also ensures that the maximum amount of tyre area is in contact with the road at all times. The system also adjusts the hydraulic pressure on the steering centering cam according to vehicle speed so that the amount of steering feel remained almost constant at any speed, counteracting the tendency of manual and ordinary power assisted steering to feel light at high speed. Thus the car turns easily at low speed, emphasized by high gearing given two turns lock-lock, and relatively more effort is required at higher speed. Many contemporary reviewers remarked that this system would take at least 50 mi (80 km) of driving to become familiar, but once the driver is accustomed to the system traditional steering feels old-fashioned.[15]

The steering actually had the same "assist" at all speeds — the steering was hydraulically locked against steering movement of the wheels from the road ("feedback") up to the capacity of the unit. Hitting a pothole at high speed would not turn the steering wheel in the driver's hands. The reduction in 'assist' was achieved by a piston/roller pushing on a heart shaped cam geared to the steering shaft (hence the one turn to full lock), which was fed with system pressure so that as its pressure rose with increasing road speed, the steering assistance seemingly reduced and the steering centering effort rose. However, full steering wheel turning was available at all speeds, though considerable force was necessary to turn the steering wheel at high road speed. Enough pressure was admitted to the centering unit to return the wheels to the straight ahead position when the car was not moving. The centering pressure was regulated by a flyweight centrifugal governor driven by the pinion (secondary) shaft of the manual gearbox and by a proportioning valve connected to the fluid pressure in the automatic gearbox, which pressure was proportional to the speed of the output shaft. The pressure increased all the way to 120 mph (190 km/h), and a subsidiary function of this feed was to turn off the air conditioning fans above 50 km/h (31 mph).

The wiper mechanism is 'sensitive' to rain, by measuring the current needed to drive the wiper motor, while the steering column is adjustable in both height and reach.

The braking system, adapted from the DS, employs disk brakes at all four corners (the DS has drums at the rear), with the front brakes being inboard, and cooled via large ducts on the front underside of the car. The hydraulic braking pressure front to rear balance is self-adjusting according to the weight in the rear of the car.

Standard wheels are steel with stainless trims, but a factory option was available for lightweight wheels made of composites. These wheels weigh less than half the standard weight and are possibly a unique application of composites on a production vehicle.

Motorsport[edit]

Breadvan short-wheelbase racing variant

The SM won its first competitive outing, the grueling 1971 Rallye du Maroc. Citroen continued rallying the SM, eventually developing a "breadvan" short-wheelbase racing variant.

Twin Turbo V6 SM developed by SM World in Los Angeles, California - achieved 202 mph (325 km/h) at Bonneville Salt Flats

SM World, a marque specialist in Los Angeles, California, produced a turbocharged SM, which in 1987 set the land speed record for production vehicles in its class at the Bonneville Salt Flats, Utah — traveling 202 mph (325 km/h).[16]

US exports[edit]

A US-spec Citroën SM with round headlamps. The unusual looking green balls are suspension components.

The main export market for the SM was the U.S. In the U.S., the market for personal luxury cars was much larger than in Europe, with competitors like the Cadillac Eldorado, Lincoln Mark IV and Ford Thunderbird alongside a large selection of Italian, British, and German imports. Nevertheless, the unique design of the SM made quite a splash and won the Motor Trend magazine Car of the Year award in 1972: unheard of for a non-US vehicle at the time.[17]

The SM's six headlight set up was illegal in the U.S. at the time and consequently, U.S. specification cars were fitted with four fixed round exposed lamps. Also, the separate glass windshields of the headlights were illegal in the USA after 1967, which is why the DS did not get them on USA cars when it was restyled for 1968, and the VW Beetle and Vanagon/Kombi and Jaguar XKE lost their headlight glass windshields at the same time.

Despite initial success, U.S. sales ceased suddenly — Citroën expected, but did not receive, an exemption for the 1974 model year 5 mph (8.0 km/h) bumper regulation imposed by the NHTSA. The integral variable height suspension of the SM made compliance impossible. The final batch of 134 now illegal 1974 U.S. model SMs were shipped to Japan.[18]

Engines[edit]

The SM was sold with a small, lightweight engine in various forms, designed from scratch by Giulio Alfieri but capable of being assembled on existing V8 tooling. Because of this, the engine sported an unusual 90° angle between cylinder banks — a trait shared with the later PRV V6. It was a very compact and innovative design that allowed the use of just one pattern for the cylinder heads and an intermediate shaft extended out to drive the auxiliaries.

The engine was aluminum and weighed just 300 lbs (140 kg).

The series production engines (always mounted behind the front axle) were:[19]

  • 2.7 L V6 with Weber 42 DCNF carburettors, "C114-1" (170 bhp) (1970–1972)
  • 2.7 L V6 with Bosch D-Jetronic injection, "C114-03" (178 bhp) (1973-1975 - Not available in the U.S.)
  • 3.0 L V6 with Weber 42 DCNF carburetors, "C114-11" (180 bhp) (1973-1975 - about 1400: 5-speed manual U.S. only in 1973, rest of the world, automatic only in 1974 & 1975)

The size of the 2.7 L engine was limited by French puissance fiscale taxation, which effectively banned large displacement vehicles. The engine was also used in the Maserati Merak from 1973 to 1982 (later versions for the Merak SS had much larger valves and a reputed 220BHP) and the Ligier JS2 sports car. The final SMs were produced in the Ligier factory in Vichy.

Fuel consumption was 19mpg, which compares favorably to such competitors as the Mercedes-Benz 450 SLC (17mpg) and the Jaguar XKE Series III V12 (12 mpg).[20]

One SM had a Maserati V8 motor - this was a test bed developed by Maserati for the 1974 Maserati Quattroporte II.[21] Despite developing (260 bhp), the car required relatively modest adjustments, and the performance made the SM into a true sporting car.[22]

One SM had a V6 twin Turbo - developed by specialist SM World for land speed record testing at Bonneville Salt Flats - achieving 202 mph.[16]

5-speed manual transmissions were fitted to most SM's. A 3-speed Borg Warner fully automatic transmission was an option in North America in 1972-73, and in Europe 1974-75.

Demise[edit]

After the 1974 bankruptcy of Citroën, Peugeot took ownership of the company and in May 1975, divested Maserati. Peugeot decided to stop building the SM, as sales were just 115 units that year.

The DS, upon which the SM was based and with which it shared many parts and subassemblies, was scheduled to be discontinued in 1975.

Observers often attribute the demise of the SM to the 1973 oil crisis and economic recession. While the oil shock certainly affected sales, it is useful to note that many far more profligate cars were introduced at the same time the SM ceased production. Peugeot even introduced a V6 powered car of similar displacement and fuel consumption in 1975, the 604. In the U.S. (the main export market for the SM), the SM was actually an economical vehicle relative to its competitors. However, the U.S. National Highway Traffic Safety Administration (NHTSA) imposed new automotive design regulations in 1974, effectively banning the Citroën from the U.S. market.

As illustrated under production numbers, SM sales declined starting in 1972. This appears to be attributable to maintenance issues. The early ignition breaker cassettes are very unreliable, and the timing chains cause catastrophic engine failure if not adjusted at 60,000 km, faults that were corrected long after production ceased. The 90° engine timing was unfamiliar to mechanics in the 1970s. Only the Buick 90 degree V6 (1962–66; 1975-), Jeep (1966–71), was an American V6 with 90° between banks.

Most vehicles require only generalist maintenance, where any competent mechanic can properly maintain the vehicle. Certain vehicles — like Citroëns and Ferraris — require specialist care due to their unique design. While a sturdy car if maintained rigorously, the SM did require two sets of specialist care — Citroën specialists, which are widespread in Europe, and a rarer Maserati specialist, to keep the engine in tune.[23] Once potential buyers began to realize this, sales dropped precipitously.

Components of the SM lived on — in the Maserati Merak (engine, transmission) and the Lotus Esprit (transmission (both mirror image)). The successful Citroën CX carried forward most of the SM's dynamic qualities, including the trendsetting speed sensitive power steering.

Production numbers[edit]

A total of 12,920 SMs were produced during its lifetime. Sales declined steeply each year following the first full year of production. The North American market took 2,400 cars, in 1972 and 1973.[24]