Citroen SM, 1972

 

 

Citroen SM, 1972

The Citroën SM was a high performance coupé produced by the French manufacturer Citroën between 1970 and 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 US in 1972.

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 - eventually becoming a halo vehicle for the brand. 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 engine.

The result was the Citroën SM (Sport Maserati), first shown at the Geneva Motor Show in March1970. It finally went on sale in France in September of that year. All produced were left-hand-drive, although some RHD conversions were done in the UK.

The SM was Citroën's flagship vehicle, competing with other high performance GTs of the time from manufacturers such as Jaguar, Lotus 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.

The SM innovated a new type of variable assist power steering that has since spread throughout the vehicle population. It allowed great assistance to the motorist while parking, but little assistance at motorway speeds. 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 chuckhole at high speed would not turn the steering wheel in the driver's hands! The hydraulic pressure to the power centering unit increased with speed, giving the impression of less and less power "assist." 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 pressure in the automatic gearbox, which pressure was proportional to the speed of the output shaft.

Contemporary automotive journalists were most effusive about the SM's dynamic qualities, which were unlike anything they had experienced prior. The SM provided a combination of comfort, sharp handling, and high performance not available in any other car at the time. Popular Science noted that the SM had the shortest stopping distance of any car they had tested. To this day this stopping distance remains outstanding.

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 litre) was used in Maserati's own Merak which, together with the Khamsin, used Citroën's high pressure hydraulics.

Styling
The look of the car was quite distinct. Designed in-house by Citroën's chief designer Robert Opron, the SM bore a vague family resemblance to the DS. Seen from above, the SM resembled a teardrop, with a much wider track at the front.

The SM was unusually aerodynamic for its era, with a very low drag coefficient. European critics marvelled at the resulting ability to travel for hours at 200 km/h (120 mph) in comfort. In addition, many of the details reflected Robert Opron's American background, notably the truncated 'fins' at the rear.

The SM combined many unusual features - lights that swivelled with the steering (except in the USA where such was illegal), unique self-centering and fully powered steering, self-leveling headlights (except in the USA where such was illegal), a wiper mechanism that was 'sensitive' to rain, and many other features that are now commonplace on the cars of today.

The SM's design was timeless; the car was even used in a 1999 television advertisement for British Petroleum of Spain, where 'a futuristic car was required'. It placed eleventh on Automobile Magazine's 2005 "100 Coolest Cars" listing.

In 1970, it was a car of the future and the fastest front-wheel drive car to be made. It was an example of the car as a symbol of optimism and progressive technology, similar to the SM's contemporary, the Concorde aircraft.

US exports
The main export market for the SM was the United States. In the US, 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, English, 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.

The SM's six headlight set up was illegal in the United States and consequently, US specification cars were fitted with four fixed round exposed lamps.

Despite initial success, US sales ceased suddenly - Citroën expected (but did not receive) an exemption for the 1974 model year 5 mph bumper regulation imposed by the NHTSA. The integral variable height suspension of the SM made compliance impossible. The law as written called for bumpers to be an exact height off the ground at all times, yet according to the laws of physics, cars dip at the nose on braking. Vehicles classified as trucks were always exempt and the entire law was eventually repealed in 1981. The final batch of 134 now illegal 1974 US model SMs were shipped to Japan.

The Engines
The SM was sold with three very similar, small, lightweight engines, all derived from the contemporary Maserati V8 fitted to the Quattroporte. Because of the V8 origin, this engine sported an unusual 90 degree angle between cylinder banks - a trait shared with the PRV V6.

The engines - always mounted behind the front axle were:

•  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 US)
•  3.0 L V6 with Weber 42 DCNF carburettors, "C114-11" (180 bhp) (1973-1975 - US 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 and the Ligier JS2 sports car. The final SMs were produced in the Ligier factory in Vichy.

5 speed manual and 3 speed Borg Warner fully automatic transmissions were fitted, but with the rest of the world outside North America only getting the fully automatic in 1974 & 1975.

The C114 is a relatively sturdy unit, provided certain modifications are performed to eliminate weak points leading to catastrophic damage:

•  The sodium filled exhaust valves may break and drop into the cylinder. Solid valves are available.
•  Primary distribution chain may wear out prematurely due to excessive vibration. A curved chain limiter should be fitted, eliminating vibration.
•  Oil pump drive shaft is underdimensioned and may break. Maserati beefed up the shaft in later versions, and this should be retrofitted if not already present.