1960s / 1970s / Citroen / French

A look at the Wankel-powered Citroën M35

citroen-m35-14In 1969, Citroën took an unprecedented approach to showcasing its engineering might: it gave a group of carefully-selected customers the opportunity to purchase and test an Ami 8-derived prototype called M35.

The highly experimental M35 was powered by a 995cc single-rotor Wankel engine developed by Comotor, a joint-venture co-founded by NSU and Citroën to design and build rotary engines. Rated at 49 horsepower and 50 lb-ft. of torque, the Wankel powered the M35 from zero to 62 mph (100 km/h) in 19 seconds – ten seconds faster than an Ami 8 – and on to a top speed of about 90 mph. Interestingly, the Wankel operated so quietly and it revved so freely that Citroën found it necessary to add an audible alarm to the tachometer that went off when the mill got close to its redline of 7,000 rpms. The Ami’s gas tank proved too small for the Wankel’s astonishing thirst for fuel so Citroën fitted a larger 11-gallon (43-liter) tank to give the M35 an acceptable driving range.

The Wankel was bolted to a new four-speed manual transmission that was commanded through a dash-mounted shifter. The setup was borrowed from the Ami 8 but the M35 had its own shift pattern. Inboard front discs and outboard rear drums handled stopping duties, while the prototype boasted a rather innovative adjustable hydraulic suspension cobbled together using a cocktail of DS and Ami 8 components.

Citroën didn’t want to build the M35 in-house so it outsourced production to French coachbuilder Heuliez. The M35 looked similar to the Ami 8 from the tip of the front bumper to the B-pillar but minor modifications were made to the front end to fit a radiator. The roof line peaked above the driver and sloped towards the rear end, creating an odd fastback-like coupe that was shorter than the Ami 8.

Inside, the M35 was equipped with Citroën’s familiar single-spoke steering wheel, seats that reclined just above the waist and a dash crafted from bits and pieces found in the company’s parts bin.

Citroën initially planned on introducing the M35 in total secrecy in order to avoid the bad publicity that a potential failure would create. Executives quickly realized the car was unlikely to stay a secret for long so the project was quietly made public.

Not everyone could buy a M35. The first setback was that it cost 14,000 francs in 1969, a hefty price to pay for a small, experimental car. To put that figure into perspective, that same year a base-model DS, the DSpécial, retailed for 13,800 francs.

The second setback was that Citroën needed to put the M35 through several hundred thousand miles of testing, so folks who only drove to the store and back once a week weren’t eligible to purchase one. Only customers who could prove that they drove at least 19,000 miles (about 30,000 kilometers) annually were considered. The third and final setback was that Citroën only planned on building 500 M35s.

The first M35s were delivered in 1969. The project was no longer a secret so each car had “Prototype Citroën M35 No.” prominently written in white letters on the driver’s side fender. Period reports indicate the M35 was brilliant to drive when it ran but its engine shared other Wankels’ tendency to self-destruct prematurely. Few M35 owners got to 40,000 miles without a full rebuilt.

citroen-m35-4

Citroën was well aware of the potential issues with rotary engines so it offered a two-year long powertrain warranty with roadside assistance on all M35s, and a loaner was provided if the car had to stay in the shop for a prolonged period of time. Each dealer’s service department was asked to take careful notes of all M35s they got in for maintenance and send them back to Citroën’s headquarters as soon as possible.

The pilot program ended in 1971. Citroën tried to buy back all of the M35s at price that was higher than the market value in order to destroy them but owners weren’t required to sell and approximately a third of the production run survived. There is catch: In the end, Citroën ended up building just 267 examples of the M35. The numbers written on the fender were adjusted to make it look like 500 were built, and rumor has it that several cars wore “Prototype No. 1” stickers.

Many aspects of the M35 made it to regular production. The rotary engine was strangely deemed satisfactory and a twin-rotor version of it was used in the GS Birotor in 1974; the gearbox used in the M35 was fitted to the GS 1015 (albeit with a normal shift pattern); certain suspension bits found their way into the GS line when it came out in 1970 and the seats that reclined just above the waist were found in none other than the SM.

The M35 today

Less than 100 M35s are currently accounted for and the vast majority of them never left France. The survivors are an elusive sight, most are stashed away in private collections or in museums and they are driven very rarely.

Examples number 388 and 160 are in a private Citroën museum in the French Alps, number 169 is on display in the Citroën Conservatoire on the outskirts of Paris and an example that oddly enough does not have a number is occasionally displayed at Volkswagen’s Zeithaus museum in Wolfsburg, Germany.

All period photos provided by Citroën’s archives department.

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5 thoughts on “A look at the Wankel-powered Citroën M35

    • They’ve made it work until now. Last I heard, they said a new rotary-powered sports car is not a priority, though they might use one as a range-extender in a Volt-like plug-in hybrid.

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