Automotive History: Three French Deadly Sins (Part 3) – Citroën GS Birotor


Here we go for the final installment of the French Deadly Sins. In doing these in chronological order (see Part 1 and Part 2 here), the juiciest Sin was left for last. This is the story of the downfall of a giant, full of hubris and shortsightedness akin to General Motors and British Leyland: Citroën and its woeful Wankel-engined waif, the 1973-75 GS Birotor.


Rotary Death-Spiral: The Citroën GS Birotor


Citroën had no sooner consumed Panhard than they faced their comeuppance. A series of bad decisions made throughout the ‘60s were soon to cause the downfall of the company, culminating in its takeover by Peugeot in 1976. Citroën committed several Deadly Sins of course, but let’s focus on a very obvious and very fatal one: the GS Birotor.


In 1967, NSU and Citroën founded the Comotor, a joint venture that would manufacture the revolutionary Wankel rotary engine for both companies. A Comotor factory was built in Saarland by 1969 and started manufacturing twin-rotor engines for the NSU Ro80 (another Deadly Sin in its own right).

The peculiar Citroën M35 had a Comotor engine; about 270 were built by Heuliez in 1969-71.

The peculiar Citroën M35 had a Comotor engine; about 270 were built by Heuliez in 1969-71.


Citroën looked into a single-rotor variant, purposefully testing the engine in a novel way: by selling it to a very limited amount of “consumer-testers” as the M35 coupé. Citroën guaranteed that the M35 owner would receive technical assistance free of charge. In exchange, owners had to clock at least 30,000 km per year in their M35, paying for gas, tyres, etc., themselves and report regularly as to their car’s performance. Citroën also promised to buy back the used M35 at a very good price. This ingenious plan enabled Citroën to try out several new concepts for relatively little risk, but at quite a cost: making the M35 wasn’t cheap (it was in fact sold at a loss) and buying them back afterwards was downright ruinous.

Pierre Bercot, Citroën CEO (1958 – 1971), made a lot of questionable decisions, including the Wankel programme.

Pierre Bercot, Citroën CEO (1958 – 1971), made a lot of questionable decisions, including the Wankel programme.


Nevertheless, it was felt that enough was now known about the Wankel engine to warrant a true production version. The CX, then still in development, was an obvious candidate, but Citroën’s bigwigs felt that waiting until late 1974, the car’s planned launch date, was probably too long. Besides, a mooted tri-rotor design would probably be better suited for the CX. A twin-rotor car should be premiered before that. (One of the findings of the M35 experiment was that a single rotor was too small for the kind of car Citroën had in mind.) But the firm wanted to do this somewhat on the cheap and hedge its bets.


The fate of NSU, the Comotor’s other partner, served as a clear warning: Wankel engines were a very risky venture. If one model were to be launched with it, said model might just sink the company. The original NSU twin-rotor had several issues, but the most damning one was its lack of durability. Some Ro80 engines gave up the ghost after 20,000km or less, leading to costly warranty replacements. Mazda, the other main user of rotary engines, also had problems with its engines.

The Comotor 624 was mounted transversally in the GS.

The Comotor 624 was mounted transversally in the GS.


Citroën were confident that their Wankel would be better prepared on this front. It was virtually the same as the NSU motor, but with the benefit of five years of additional testing. The water-cooled twin-rotor displaced 995cc, producing a commendable 107 hp (DIN) @ 6500 rpm – a little less than the NSU unit. The apex of the rotors were the key, and Comotor had devised better and far more durable apex seals by the early ‘70s. The question was: what car would serve as the host for the hot new engine? The DS was seen as too passé, so it had to be the new mid-range car, the Citroën GS.


To save money, virtually nothing would be different on the GS Birotor (named GZ in Citroën’s internal documentation) compared to its flat-4 siblings. The plush Pallas version, with carpets and seats so soft they felt like buttered marshmallows floating on a bed of helium balloons, was selected. After all, the Birotor would be the range-topping GS. Externally, only the flared wheel arches gave the car away as a Wankel model, dictated by wider tyres. The other giveaway was the colour scheme: two-tone brown or gray. But any money saved by making the Birotor outwardly identical to the normal GS was spent in the Wankel model’s bespoke platform, larger fuel tank, post-combustion exhaust system (that literally cooked anything in the trunk) and transmission.


Inside, the GS’s curious collection of gauges and lights gave way to a very no-nonsense (but a tad crude-looking) array of round Jaeger dials. The message was: this car’s engine needs to be closely monitored, so we don’t want the driver to be distracted by our usual Citroën quirks. Oleo-pneumatic suspension was included as on the other GS models of course, as were hydraulically-powered brakes and steering. The transmission was based on the NSU Ro80’s semi-automatic design: a three-speed box operated via a floor-mounted shifter.


The GS Birotor came out mere weeks before the 1973 OPEC oil embargo. One of the Wankel’s known faults was its prodigious thirst. Compared to the 1.2 flat-4, which was already criticized for its appetite, the GS Birotor drank a minimum of 13 litres / 100 km (18 mpg). The sale sticker also proved rather unpalatable for the average buyer: FF 25,000 – as expensive as a low-spec DS for a car that looked virtually identical to a FF 15,400 flat-4 GS.


Unsurprisingly, the GS Birotor was a sales disaster. With fewer than 700 cars sold in 1974, the game was up before it started. Citroën were hemorrhaging cash on all fronts by this point: Maserati, which they had owned since 1969, was deep in the red; the GS programme, which had cost the company so much, was not profitable with the Birotor; DS sales slumped as the new CX was launched; the flat-4 engined Ami Super was a complete flop; SM sales dwindled to nothing. The investments sunk into new factories, as well as the new flagship CX were substantial, but at least the CX might succeed in making money one day. Only the 2-cyl. cars were still selling somewhat – but for meagre profit. Mid-1974, Citroën had over 120,000 cars in stock and were looking at a loss of FF 500 million that might double by the year’s end.


Bankruptcy loomed and crisis talks were brokered by the government. Michelin, Citroën’s main investor since 1935, wanted out. Maserati was sold off immediately to De Tomaso; Berliet, a truck-maker absorbed by Citroën in 1967, was purchased by Renault, much to Michelin’s dismay. The French government having vetoed any foreign buyout of Citroën (Fiat had been circling the skies above for years) and given Michelin’s strong aversion to nationalization (i.e. selling to Renault), there was but one viable solution: Peugeot.

Citroën's mass extinction event of 1975-76. Only the DS got a farewell party.

Citroën’s mass extinction event of 1975-76. Only the 19-year-old DS got a farewell party.


In December 1974, the lion bought 35% of the double chevron. The takeover took about 18 months to finalize. In the meantime, Citroën stopped making the DS and the SM by 1975 and the Ami Super by 1976. But the first to go, the no-brainer, was the GS Birotor, which was put out of its misery in January 1975, having tallied only 874 sales in 18 months.

A rare survivor I captured a while back…

A rare survivor I captured a while back…


Soon, Citroën began to actively seek out all GS Birotor owners to offer them a huge rebate on a new CX. Citroën (and Peugeot) determined that the financial liabilities involved in keeping even the very limited number of GS Birotors in circulation outweighed all other considerations. Comotor was going to be wound down due to the planned death of NSU in 1977 anyway. With all surviving GS Birotor warranties null and void, Citroën destroyed all of those it had bought back from its clients, especially the engines. Hydraulic punching machines were used to pierce all the Wankel blocks to make them unusable and a special government order was issued exempting Citroën from keeping any GS Birotor parts in their inventory.

…And another one I snapped a few years later.

…And another one I snapped a few years later.


Very few GS Birotor made it to the present. Having talked to an owner once, it seems the engine itself is pretty durable – it was probably one of the best rotary cars of the ‘70s. Perhaps if Citroën had waited a couple of years and put the Wankel in the CX, things might have turned out differently. The engine was tested on the CX extensively as late as 1979. But as it played out, it was a poorly reasoned attempt from Citroën: the engine and the price of the car did not match the image of the GS, a reasonably-priced small family car. Because they wanted to keep spending to a minimum, Citroën made an expensive car that looked like a cheap one, which would have been sales poison even without the Oil Shock. Of course, the timing of the launch was critical in making the downfall so dramatic and nudging Citroën toward insolvency. The GS Birotor wasn’t the only albatross around its maker’s neck in 1974, but it was the newest and most expensive one. And when an automaker actively seeks to buy back its product and send every unit to the crusher, it feels as if they knew that was their Deadliest Sin.


Sic Transit Gloria Mundi


So there we have it, three Deadly Sins from three decades that killed three French automakers in the ‘50s, ‘60s and ‘70s, including one of the French “Big Trois” (Citroën, Peugeot, Renault). There are plenty of other DSs out there though. A British edition could be pondered, for instance…


Related CC posts:

Cohort Classic: Citroën GS – One For The Anoraks, by Perry Shoar

Curbside Classic: Citroën GS 1200 Club Break, by JohnH875