Mazda RX-7: The wonder of Wankel (2024)

The Mazda RX-7 is one of motoring’s boldest success stories, as the men from Hiroshima put their faith in Felix Wankel’s rotary engine when all others had cast it aside.

It was a high-risk gamble on unproven technology that had killed off fellow early adopter NSU and nearly did for Citroen, but it paid off spectacularly.

With more than 800,000 made over 24 years, the always good-looking RX-7 cemented Mazda’s reputation not only as a technology innovator, but also as a maker of great sports cars.

We look back at the car, and its extraordinary engine.

When the Mazda RX-7 was launched in Japan in March 1978, the Wankel rotary engine was very much in the last chance saloon.

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Patented in 1929, it wasn’t until after the war that work began in earnest to transform the engine from unreliable prototype into a robust production engine.

NSU and Mazda joined forces in the early 1960s to jointly develop the small, lightweight, free-revving unit that provided smooth, vibration-free running.

The German company won the unofficial race to get it into a production car, 1964’s Bertone-styled NSU Spider, followed by the ill-fated Ro80 saloon in 1967.

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But Mazda had used their time wisely, using carbon-aluminium to solve the problem of catastrophic wear to the rotor tip seals that plagued the NSUs.

The Germans had found a similar solution by 1970, but warranty payments from those earlier ruined engines crippled the company, which was bought by Volkswagen and merged with Auto Union to create Audi.

That’s not to say things had been plain sailing for Mazda – their first attempts at rotary-engined cars suffering from poor fuel consumption that almost proved ruinous when the 1973 oil crisis hit.

Early Mazda rotary cars

The Cosmo, or 110S, a very pretty sports coupe, was Mazda’s first foray into Wankel-engined production cars.

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To prove the engine’s reliability, Mazda entered two mostly stock Cosmos into the ​​84-hour Marathon de la Route at the Nurburgring, with the pair running fourth and fifth of 60 cars for much of the race.

One car retired in the 82nd hour with axle damage, but the other completed the course in fourth.

Seen very much as a ‘halo car’ to showcase Mazda’s commitment to innovative technology, they were hand-built at a rate of one a day, with only 1,176 produced between 1967 and 1972.

At the same time, however, the company was putting rotary units into other cars – alongside a traditional piston-driven option – and this became a bit of a problem when fuel prices rocketed in 1973.

Rotary engines appeared in the Capella-based RX-2, Grand Familia-based RX-3, and the RX-4, a larger car known in Japan as the Luce.

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To put things into perspective, Motor magazine tested an RX-4 in 1973 and recorded just 14.3mpg from a car capable of a shade over 100mph.

When petrol prices shot up following the Saudi Arabia-led oil embargo starting in October 1973, buyers – particularly in the huge US market – quickly turned to vehicles with better fuel economy.

Sales of greedy rotary cars suffered and, combined with Mazda’s relatively inefficient productivity, over-reliance on the US market, and existing debts, the company was on the verge of bankruptcy by 1975, only saved thanks to intervention by the Sumitomo Bank and the carmaker’s subcontractors and distributors.

Rather than give up on the Wankel engine completely, Kenichi Yamamoto, managing director of parent company Toyo Kogyo and an expert on rotary engines, fought hard for its survival. He got his way, and the RX-7 was born.

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Development of the RX-7

Rotary power continued to perform well for Mazda in motor racing so, rather than try to convert the world to Wankels in mainstream cars, engineers at Hiroshima went back to its roots as a sports car engine.

As it proved in the Cosmo, the lightweight Wankel unit was perfectly suited to a compact sports coupe, and work began to develop Mazda’s first mass-produced sports car.

Replacing the very different Savanna RX-3, the only things the new car shared with its predecessor was its 12A Wankel engine and its name prefix.

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Designed by lead stylist Matasaburo Maeda, the Savanna RX-7 was launched in Japan in March 1978, its low capacity twin-rotor engine a boon for home customers who paid less road tax than piston-powered cars of larger capacity which offered similar performance.

For the uninitiated, it’s worth taking a quick look at what lay beneath the bonnet of the RX-7, and how this unique engine works

The engine features two oval chambers displacing 573cc each, a total of 1,146cc, in which triangular rotors rotate, replacing the pistons in a traditional engine and completing the Otto cycle of intake, compression, ignition and exhaust in an entirely different way.

As the three-tipped rotor travels around the chamber, it moves past the intake port and draws in the fuel / air mixture, the next rotor tip sealing the chamber when it, too, passes the intake port.

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The rotor continues on its journey, and the chamber containing the fuel / air mixture becomes smaller, compressing the mixture and allowing combustion to start via traditional spark plugs.

Once the rotor tip passes the exhaust port the spent gasses are expelled, with power to the flywheel delivered by an eccentric shaft.

The benefits included a lighter, smaller unit; a greater power output relative to engine capacity and weight; and fewer moving parts.

Perfect then, for a sports car.

Taking America by storm

The first generation RX-7, known as the SA22C or FB, took the American market by storm when it was launched there in May 1978.

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By June the following year, Mazda was selling 5,000 cars a month in the US, many more than close competitors on price and performance, the Porsche 924 and Datsun 280ZX.

It didn’t reach UK showrooms until September 1979, by which time it was already a familiar sight to British motor-racing fans, with Tom Walkinshaw’s Pentax-sponsored RX-7 then leading the British Saloon Car Championship.

Although clearly a slippery sports car, it sneaked into the BSCC because its internal dimensions complied with the FIA saloon car regulations, much to the annoyance of its rivals.

Although Walkinshaw would ultimately finish second to Richard Longman in a Mini 1275GT, Win Percy took the next two titles in a TWR-prepared RX-7.

In road form, the engine produced 105bhp at 6,000rpm and 106lb ft of torque at 4,000rpm, with a drag coefficient of just 0.36, with the car hitting 60mph in just under 9 seconds on its way to a top speed of 121mph.

Mazda claimed to have improved fuel economy by 40 per cent, resulting in about 27mpg in mixed use and 33mph at a constant 56mph.

Oil consumption is also relevant, however, as the rotary engine has a total loss system, using oil to lubricate the gas seals by metering oil into the combustion chambers. A car tested by MotorSport magazine used three quarters of a litre in 600 miles.

The compact size of the engine meant it could be sited in a “front mid-engine” position, well back behind the axle centre-line, to permit a 51/49 weight distribution, producing sharp handling.

Its attractive styling was described as a modern take on Colin Chapman’s Lotus Elan Plus 2, but with added hatchback capability from its opening rear window.

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RX-7 in the UK

The RX-7 was received warmly by British road testers, Clive Richardson of MotorSport describing it as “civilised everyday transport for the discerning motorist of the ‘80s, a softer breed than he of the ‘60s. But the RX-7 still has enough of that fun factor to make it highly enjoyable.”

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So free-revving was the engine that Mazda thoughtfully added a warning chime if you injudiciously strayed above the red line of 7,000rpm (to no discernible benefit).

To Richardson, the engine was “uncannily smooth and vibration free”, “a league away from the old hairy-chested sports car theme, a delightfully civilised and practical sports car which should hold no qualms for the inexperienced and give plenty of pleasure to the experienced”.

Motor magazine’s testers considered the RX-7 good value for money at £8,549 compared with the 924 (£9,103) and 280ZX (£9,582), especially given the “astonishingly smooth” engine throughout the rev range, “whether you are pottering about at modest revs or bringing in the full force of all four barrels to surge through the rev 7,000rpm red line”.

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“To a man our testers liked the RX-7, differing only in the degree of their enthusiasm,” the magazine reported. “It’s a very satisfying driver’s car, with thoroughly entertaining handling, tireless brakes…and outstanding smoothness of that rotary engine.”

Despite this glowing praise, the car was less of a sales success in Britain than in the US because of lingering suspicions about thirst and the durability of rotary engines and, probably, badge snobbery.

The Mazda was, after all, trying to pinch sales from Porsche and its entry-level 924.

In 1981, the RX-7 received some cosmetic changes and upgrades, including integrated plastic covered bumpers, wraparound tail lights, a five-speed gearbox, redesigned interior, and an increase in power to 115bhp and torque to 112lb ft.

At £8,699, it was priced just below the Porsche and well below the Alfa GTV6 it was pitted against for a CAR road test in August ‘81.

The magazine marvelled at the RX-7’s sweet rotary engine: “The faster it turns, the sweeter it hums and you cannot but marvel at the uncanny smoothness.

“So effortlessly does the rotary spin that it feels far less strained at 7,000rpm than the Porsche does at half the revs.”

Engines upgrades and a turbo

Over in Japan, in September 1983 the RX-7 got a turbocharged engine rated at 163bhp, the specially modified “Impact Turbo” operating 20 per cent faster than usual to deal with the different characteristics of the rotary unit.

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It was short-lived because the mk 2 RX-7 was close to production, but it was a taste of things to come for Mazda’s revolutionary sports car.

Meanwhile, the final iteration of the mk 1, the series 3, was launched in 1984, with US cars getting the GSL-SE model with a fuel-injected, 1,308cc engine producing 135bhp.

Because of its extra performance, it received larger disc brakes front and rear and stiffened suspension.

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By the end of its production run, the mk 1 had sold 474,565, with nearly 80 per cent of them heading to America. It was named seventh on Sports Car International magazine’s Top Sports Cars of the 1970s, sandwiched between the Ferrari Dino in sixth and the Porsche Carrera RS in eighth.

However, sales had started to drop worldwide, and Mazda recognised that engine power had become a problem compared to its competition led by the 924S.

Head to head with Porsche

Whereas the first RX-7 was inspired by the lightweight Lotus Elan Plus 2, Mazda aimed the second generation squarely at Porsche’s 924 and 944 – and it showed.

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With the bulk of cars sold in the United States, chief project engineer Akio Uchiyama paid close attention to the views of American buyers before opting to move away from the rawness of the mk 1 and more towards the sports touring 944, which was selling well at the time.

The new car was 800lb heavier than its predecessor, but power was up to 146bhp from a 1,308cc fuel-injected, twin rotor unit, with torque up from 112lb ft at 4000rpm to 134.5lb ft at a more useful 3000rpm.

It pushed the RX-7 FC to 60mph in 8.2 seconds, less than half a second slower than the Porsche but, at £13,995, also £1,500 cheaper.

To compete with the Porsche’s handling, rack and pinion steering replaced the sometimes vague recirculating-ball system of the earlier car, while the live rear axle was switched to a more modern, fully independent system, along with a Dynamic Tracking Suspension System (DTSS) that aided stability.

Adding a turbocharger improved output to 182bhp, upped to 200bhp for the 1989 model, while a power-operated convertible was added to the range in 1987.

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Despite its extra weight, the mk 2 sold well – 86,000 in the US alone in 1986 – and won plaudits from the motoring press, winning Motor Trend’s Import Car of the Year for 1986.

Only in Australia was there demand for a more stripped back, lighter RX-7, sith a run of 250 “Sports” models with no power steering, power windows or rear wiper.

To celebrate 10 years of the RX-7, Mazda produced a turbo model limited to 1,500 examples featuring a Crystal White paint scheme, white 16-inch seven-spoke alloy wheels, a black leather interior, and a gold rotor-shaped 10th Anniversary Edition badge on the front wings.

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Finally, there was a lightweight GTU model built to commemorate the RX-7’s domination in America’s IMSA GT Championship.

The normally-aspirated car dispensed with electric windows and a rear wiper, while the sunroof and air conditioning were optional extras.

Ventilated front and rear discs as fitted to the turbo model were standard, along with a 4.300 type viscous limited slip differential unique to the model.

Its 16-inch wheels were shod with 205/55VR tyres, and the GTU – for Grand Tourer Under 2.5L – had speed sensing power steering for improved feel at higher speeds.

Japan’s best-looking car?

The third generation RX-7, the FD produced from 1992, was hailed by Autocar as “the best-looking car to come from Japan”, and by CAR magazine as “gorgeous”.

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It was all handsome curves, unusual shapes and imaginative forms, and a departure from its Porsche-aping predecessor; it was also larger, and no longer small enough to qualify for road tax breaks in its native Japan.

Now in the “upper-level luxury sports car” category because of its width, Mazda had already compensated for the loss of home sales by creating the Elan-inspired MX-5 and small MX-3 coupe.

Power came from a twin-rotor 1,308cc engine with a sequential twin turbo system developed in conjunction with Hitachi, with the second turbocharger taking over from the first from 4,500rpm to the red line.

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It ensured a consistent delivery of power and torque throughout the rev range, and pushed out 252bhp and 217lb ft of torque, significantly more than earlier models and pushing up to 272bhp and 231lb ft by the end of its production run.

Although it now looked nothing like a Porsche, Stuttgart’s finest was still firmly in Mazda’s sights, this time taking aim at the new entry-level 968.

Autocar was suitably impressed: “This time, the world now knows, Mazda’s new RX-7 is playing for real. In third-generation form, now on sale in the UK, the oddball Porsche pretender with the rotary engine hasn’t just caught up, it’s stolen a march.

“Look at that bloody design: what else in this class looks remotely as sexy? Potentially Mazda’s most vicious and effective weapon yet.”

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CAR described “the company’s most convincing sportster since the MX-5, and it’s the best looking”, a 968-beater and a true junior supercar with 60mph reached in 5 seconds and a top speed of 160mph.

“Over 2000 revs there is a wonderful seamlessness about progress: no booms, no engine zings, no vibrations,” it wrote. “The rotors, supercharged by the blowers, feel as though they would spin themselves to destruction without the slightest sign of struggle or strain.”

However, one or two found the FD a little too civilised, especially compared to the no-frills, US-spec R1 race-derived version.

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Was the RX-7 too luxurious?

Autocar, having praised the car’s looks, felt that the UK import version was a corruption of the RX-7’s “basic tenet of lightness and purity of purpose”.

“Don’t get us wrong; we’re not saying this UK-spec car is in any way ponderous but by loading it with every extra we can’t help feeling Mazda UK has interfered too strongly (and almost spoilt) the fundamental concept.

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“Not so handicapped, the RX-7 would, we have no doubt, already be the sports car sensation of the ‘90s and an instant classic. As it stands, the best-looking car Japan has yet produced isn’t quite the giant killer we were hoping for.”

Writing in MotorSport, Andrew Frankel said of the disparity between the US’s road-racing R1 and the UK version: “Sitting in leather lined, air-conditioned, cruise-controlled comfort, it struck me that, for all these extras, something rather more important had perhaps been lost.”

Despite performance that was “close to ferocious” when the second turbo charger kicked in, Frankel found it hard to reconcile such power with the “flat note of the rotary engine”.

“For a car to look and perform like this but to sound rather less interesting than an electric hedge-trimmer stands in this book as a grave fault,” he said.

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Nevertheless, the RX-7 deserves its place in history as a unique sports car and one of the few to make a success of the rotary engine.

It was followed by the RX-8, which sold more than 190,000 units before the rotary engine fell foul of European emissions regulations in 2010, continuing in Japan only for another two years.

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Ultimately, Mazda was rewarded for its bravery in persevering with Felix Wankel’s groundbreaking technology with huge success in America, later followed by the globally massive-selling, conventionally-engined MX-5.

With electric vehicles, or maybe something else, phasing out petrol in the not-too-distant future, we will almost certainly never see its like again.

As an automotive enthusiast and expert with a deep understanding of the Mazda RX-7 and its revolutionary rotary engine, let me provide a comprehensive breakdown of the key concepts and historical context mentioned in the article:

  1. Introduction to the Mazda RX-7:

    • The Mazda RX-7 is hailed as one of the automotive industry's success stories, emphasizing Mazda's bold decision to embrace Felix Wankel's rotary engine technology.
    • The rotary engine was considered a high-risk gamble, especially after the challenges faced by fellow early adopters NSU and Citroen.
  2. Background on Wankel Rotary Engine Development:

    • The Wankel rotary engine was patented in 1929, but significant development began after World War II to transform it from a prototype into a reliable production engine.
    • Mazda collaborated with NSU in the early 1960s to jointly develop a small, lightweight, and free-revving rotary engine, which eventually found its way into the Mazda RX-7.
  3. Challenges and Innovations:

    • NSU faced challenges with wear to rotor tip seals, which Mazda addressed by using carbon-aluminium, solving the problem that plagued NSU.
    • Mazda's early rotary-engined cars faced issues like poor fuel consumption, exacerbated by the 1973 oil crisis, which led to a decline in sales.
  4. Early Mazda Rotary Cars:

    • The Mazda Cosmo (110S) was the first rotary-engined production car, serving as a "halo car" to showcase Mazda's commitment to innovative technology.
    • Other rotary-engined models included the RX-2, RX-3, and RX-4, with varying degrees of success.
  5. Financial Struggles and Survival:

    • Mazda faced financial challenges in the 1970s due to poor fuel economy, over-reliance on the US market, and existing debts.
    • Kenichi Yamamoto, an expert on rotary engines, fought for the survival of the Wankel engine, leading to the development of the Mazda RX-7.
  6. Development of the RX-7:

    • Mazda transitioned the rotary engine from mainstream cars to sports cars, highlighting its success in motorsports and its suitability for compact sports coupes.
    • The RX-7, launched in 1978, featured a lightweight Wankel unit, providing excellent power output relative to its size and weight.
  7. First-Generation RX-7 (SA22C or FB):

    • The first-generation RX-7 gained popularity in the US, outselling competitors like the Porsche 924 and Datsun 280ZX.
    • Noteworthy features included the lightweight rotary engine, attractive styling, and competitive pricing.
  8. RX-7 in the UK:

    • The RX-7 received positive reviews in the UK, with commendations for its smooth rotary engine, handling, and value for money.
    • Sales in the UK faced challenges due to lingering concerns about rotary engine durability and competition with established brands like Porsche.
  9. Upgrades and Turbocharging:

    • The RX-7 received cosmetic changes and upgrades in 1981, including a turbocharged engine for the Japanese market.
    • Turbocharged models and series 3 variants were introduced, enhancing performance and addressing concerns about rotary engine reliability.
  10. Second-Generation RX-7 (FC):

    • The second-generation RX-7 aimed at competing with the Porsche 924 and 944, featuring a more powerful and fuel-injected twin-rotor unit.
    • Significant changes, including rack and pinion steering and a fully independent rear suspension, contributed to its success.
  11. Third-Generation RX-7 (FD):

    • The third-generation RX-7, produced from 1992, received acclaim for its design and performance.
    • It featured a twin-rotor engine with a sequential twin-turbo system, delivering increased power and torque compared to earlier models.
    • The FD RX-7 targeted competitors like the Porsche 968 and received praise for its aesthetics and performance.
  12. Legacy and Conclusion:

    • The RX-7 is acknowledged as a unique sports car that successfully embraced the rotary engine, contributing to Mazda's success.
    • The article concludes with the mention of the RX-8, which followed the RX-7 but faced challenges due to changing emission regulations.

In summary, the Mazda RX-7's journey from a risky gamble on rotary technology to becoming a celebrated sports car showcases Mazda's resilience, innovation, and success in the automotive industry. The article provides a detailed account of the historical context, technological advancements, and the impact of the RX-7 on the automotive landscape.

Mazda RX-7: The wonder of Wankel (2024)
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