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A Comprehensive History Of The Wankel Rotary Engine


The history of the automotive industry boasts some of the greatest triumphs of the world to date. Henry Ford’s automation of the assembly line literally changed the landscape of production, the creation of high-speed roads meant people could travel hundreds of miles in hours instead of days. And companies like Tesla and Rimac have changed the way we feel about an all-electric future.

But with the highs come the lows. Detroit, once one of the richest cities in America has been left empty, still echoing with the success of the American auto industry, but now left to slowly decompose. People lost jobs, they lost their homes…

Detroit’s Packard Bridge Collapses

Legends have been built and torn down. John DeLorean was ripped apart after showing so much promise and potential, but left only with large debt, and the memories of what is remembered only as a prop from a film. This industry takes no prisoners.

Innovation can be difficult. It’s hard for a market to accept a new technology. Usually it doesn’t, but only one thing has failed, but yet been so loved by so many enthusiasts. This is the story of an engine. How it rose to fame, won races, but ultimately was killed by the company that adopted it. This is the prisoner that got away. This is the story of the Rotary Wankel engine.

Chapter 1: Felix Wankel Is Born

We begin in Germany. It’s 1902 and the country’s advance to industrial maturity is in full swing with steel being produced left, right and centre. In Lahr, a baby with the name of Felix is born to Gerty and Rudolf Wankel. They’re not a wealthy family, and after his father was killed in World War 1, Felix and his mother were struck with poverty.

This turned out to be a great strain on young Felix, who eventually left school with no qualifications in 1921. What he did have though, was the idea that he would produce an engine never before seen by the world.

See, Felix may have not been academically nurtured, but his mind was alive with the mechanics and engineering that he taught himself from books. He ran a machine shop after work with his friends and eventually, working towards this life long dream, he was granted a patent for the Wankel rotary engine in 1929.

Felix’s life was long and interesting, and is certainly worthy of a GTN story soon, but let’s continue following the rotary and its design.

Chapter 2: How The Rotary Works

Suck, squeeze, bang, blow. No, that’s not what you’re thinking. These are the four main stages of an internal combustion engine. While the rotary adheres to these four stages, there are some huge differences between it and piston engines. The most obvious being that Felix gave a big two fingers to the piston and instead used a rotating (believe it or not) triangular chunk which is pushed around by combustion.

It was lighter, smaller, and simpler. But while in theory this sounds to be the perfect engine, it had one major fault. Oil had to be injected straight into the combustion chamber to lubricate something called apex seals. Those of you who have owned rotary powered cars are trembling right now, aren’t you.

This oil would burn off eventually, so if you didn’t keep on top of maintenance, or even use the wrong oil, your seals would degrade leading to an engine with low power, low compression, and… basically you might as well cut a hole in the floor and push yourself along flintstone style.

With this in mind, enter the first ever car powered by a rotary.

Chapter 3 – The First Ever Rotary Powered Car

NSU, a German motorbike company took the designs from Felix and with his help in 1951, started preparation to successfully put one in a car.

The first engine was called the DKM motor. It could reach high revolutions per minute and both the rotor and housing spun on separate axis. It even produced 21 horsepower. But, for a simple spark plug change, the whole thing would need stripping. This obviously wasn’t a viable option, so a second was built. The KKM.

It was simpler, only the rotor spun, but with Felix now not involved with the production to the point he didn’t even know about it until later on, he wasn’t so happy. He complained that they had turned his race horse into a plow mare.

1960 came and everyone wanted a slice of the pie. NSU was to put their efforts into lower-powered rotary cars, Curtiss-Wright, an american firm was to use them in aviation, and automakers like Alfa Romeo and Ford, to Porsche and Rolls-Royce wanted in. And, of course, Mazda.

Eventually in the late 60s, Rolls produced a diesel version, and Citroen placed one in their M35, GS Birotor, and even their RE-2 helicopter. Mercedes-Benz, didn’t expect that name did you? They put it in their C111 concept car. There was even the hint of a rotary corvette concept from GM.

But before this, in 1964, NSU paved the way with the first ever rotary car on the road, the NSU Spider. It was listed for only 4200 euros and looked spectacular. The engine was in the back for better weight distribution, and because it was so small, you could still use the boot as well as the front boot for storage. Eat your heart out Tesla.

The first was raffled straight off the assembly line to an employee. But soon the commotion dropped. They expected to sell 5000 units a year, but in its three years of production they hardly managed half of that. But why was that? It could rev to over 6000rpm, it was smooth and provided better performance than piston engines of that era, and it was fast. 50hp fast. Well, it was those pesky apex seals.

The car very quickly became known for its unreliability, and this hit sales hard. That hasn’t stopped it from being a collection-worthy car though. These days, one in good nick will set you back around 30 to 40 thousand pounds. Unfortunately for NSU, the repairs to all the cars that went wrong set them back terribly, as well.

Chapter 4 – A Second Attempt

– The Ro 80

NSU tried once again to make the Wankel engine commonplace on the road, this time via a luxury car called the Ro 80. Its side profile had a wisp of Citroen DS about it, it had a drag coefficient of only .36, and it was beautiful. But the main attraction was under the bonnet.

This time, they’d doubled up, and the now twin rotor produced 115hp. Twice the engine, oh, twice the issues. A well cared for specimen would barely make 30,000 miles due to suicidal apex seals. Surprisingly, despite this, the car won the car of the year award. But the damage had already been done. NSU’s accounts ran red with the debt of rotary repairs and eventually gave in to VW who bought the company a couple of years later.

Another car rolled by but was simply too expensive, so VW moved the company into the Audi NSU Auto Union AG subsidiary of VW, and moments later, this became Audi, killing NSU in the process.

Chapter 5 – Mazda’s Attempt

– The Mazda Cosmo

There was one company left that fancied the challenge of the Wankel, and that was Mazda.

Led by Kenichi Yamamoto, 47 young engineers formed the rotary engine research department with a mission that was compared to that of the Shijyu Shichi Shi. This was a legendary band of 47 samurai warriors who dedicated their lives to avenging the death of their master. With the same unparalleled loyalty and perseverance, these engineers would live and breathe rotary.

They focussed on the main culprit – the seals. They tried using every material they could imagine including the bones of horses and cows. But every trial failed.

That was until 1963, when they tried modifying the shape of the seal. It was a cross-hollow seal with a cross-shaped hole near the apex, but more importantly, it worked. Mazda quickly set up shop and began making the Mazda Cosmo for a 1967 release.

– The Mazda Cosmo racing the Marathod de la Route

Like the Ro80 it had a twin rotor called the 10A. But unlike the Ro80, it was reliable. So reliable in fact, they took it racing. For 84 hours on the Marathon de la Route. It’s a 3000 mile road race through Belgium, Germany, Austria, Italy, Yugoslavia, and back again. It’s gruelling for the drivers, let alone the cars they pilot.

Mazda entered two cars, the only changes to these cars being the addition of a novel side and peripheral-port intake system. This increased the power to 130PS over the stock 110. But while one didn’t finish due to rear axle damage, the other finished in fourth place behind the likes of Porsche 911s and a Fulvia.

This near-podium win would plant the seeds for Mazda’s affinity to endurance racing in the future all the way up to the 787B’s victory in 1991. We’ll get to that later.

Chapter 6 – The Rotary Evolves

The Cosmo made it to the early 70s, as did a new rotary powered car called the R100. It was a surprising hit in the US during 71 and 72 but bad luck struck again as an energy crisis hit the industrial countries of the world hard.

Fuel was hard to come by, pushing prices up globally, but the United States felt it more than most. Its economy crumbled, crippling its auto industry with it.

Gas guzzlers just couldn’t thrive in this world, so small, efficient imports filled a much-needed gap in the market. If only Mazda had such a thing…

Chapter 7 – The RX Line Is Born

– The Mazda RX3

It was at this time, Mazda began the RX line of rotary powered vehicles. Their small engines meant road tax was much cheaper in their home country, and better fuel efficiency pushed sales rapidly in the US. But it was the RX3 that started something very special.

It was a great road car with what ended up being a 12A rotary under the bonnet for the US market. This was basically a bored out 10A with 130 horses and 115lb ft of torque to play with. But to be honest, it didn’t need this kind of power. Because…

The year it was revealed, it spawned a successful racing program where it scored a win at its very first outing, the 1971 Fuji 500. It went toe to toe with C10-era Skylines, and unlike plenty of other cars, came out the other end with its dignity, not only intact, but fueled.

This racing prowess didn’t falter either, with it accumulating over 100 victories by 1976.

Around the same time in 1974, Mazda released the RX4, which was a larger version of the RX3. Mazda called it a ‘personal luxury coupe’, and it featured a more powerful rotary engine, but Mazda new that it could pull in more American sales by aiming for their hearts. A pickup truck.

1974 also saw the release of the REPU. You know what that stands for? Rotary engined pickup. Mazda called it the pickup with pickup, and just in case you didn’t recognise the tell-tale sound emanating from the exhaust, it had ‘rotary power’ stamped across its tail. But the world still wanted more. They wanted more from Mazda, and they wanted more from the rotary engine.  

1978 came, and the RX7 was born to sit alongside Mazda’s two other remaining rotary products, the RX4, and the Cosmo, which is now back in its second iteration but now under the name of RX5.

By this point rotaries were getting pretty strong, and boost was becoming a viable option. But at the same time, piston engines were getting more efficient with electronic fuel injection slowly becoming commonplace to coincide with emissions regulations. It was at this point, although no one really realised it, the Wankel engine started a fight that it could never really win.

But, the production of the RX7 continued, fuelled by the experience gained from Mazda’s extensive racing program. In 1986, everything just clicked and the RX7 Turbo 2 was released. Its high revving engine was perfect for spooling a turbo, producing 182hp with later models producing 200. The aftermarket scene exploded, and by the time the RX7 FD was released in 1992, rotary culture was immortal.

The RX7 built upon the history of success by being the first mass-produced sequential twin-turbocharged car and towards the end of its life was producing almost 300hp. It was a seriously fast car with MotorTrend dubbing it car of the year and PlayBoy comparing it to the Dodge Viper.

But again, disaster struck. The fancy sequential system was complicated and readily went wrong meaning that even after a missive price drop to £25 grand, it hardly sold in the UK. Japanese sales were also low due to noncompliance to dimension regulations. The rotary engine had begun the downward spiral that would eventually lead to its death.

But it had one thing to fall back on.

– The Mazda 7876B 4 Rotor

The first RX7 had been pushed into the 24 hours of Le Mans, and while it failed miserably, Mazda was not going down without a fight. So in 1991, they entered a 4-rotor powered racing car called the 787B, and for the first time in history, Japan won the Le Mans. The rotary engine was later banned from the Le Mans, but they held the title as the only Japanese winners until last year, where Toyota won. Over its life the RX7 performed well in races such as 24 hours of Daytona and the British Touring Car Championship.

Unfortunately this wouldn’t help, and low sales forced the RX7 to be discontinued.

The RX8 was the final hurrah but was still plagued by higher costs than the majority of other engines on the market despite its new RENESIS Wankel engine which was supposed to lower emissions and improve economy. Research was even done into the conversion to hydrogen fuel, but obviously that never took off.

The RX8 could never hold a candle to its predecessors, so when it died, so did its engine.

Chapter 8 – The Rotary’s Demise

Throughout its life the rotary always had weaknesses. Whether it was its poor reliability, poor economy, or the fact that the market simply didn’t trust it. It was doomed before it started.

But its place in car culture will never diminish. It was the hero car in one of the most popular car films in the world, they can always be seen winning races at drag strips, and they’ll always rack up views on YouTube.

But what was the main reason for its demise?

Looking back through its history there’s one thing that really stands out: it’s racing success. Road cars need to adhere to rules, they need to be cheap to repair, and they need to align with what the market is prepared to pay for. In racing, these preferences aren’t as important to a certain degree and therefore, there’s more leeway. Engineers aren’t afraid to rebuild engines each year, and they’re certainly not afraid to throw money at it, within reason.

So really, it was us that killed the rotary. It was our high expectations and regulations that pushed the engine to breaking point. And although there have been rumours of its return and concepts cropping up every once in a while, I think we need to be prepared for the most likely of eventualities.

The rotary is dead, and I don’t think it’s coming back.

 

Written by Alex Harrington

Alex started racing at a young age so certainly knows his way around a car and a track. He can just about put a sentence together too, which helps.

He has a great interest in the latest models, but would throw all of his money at a rusty old French classic and a 300ZX.

Contact: [email protected]

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