10 Things Only Real Mazda Enthusiasts Know About The Wankel Rotary Engine

A deep dive into the iconic rotary engine and how it has done more than build a name for the Mazda brand

Mobility has come a long way since the diverse propulsion inventions of the 19th century. From Etienne Lenoir’s gasoline-powered hippomobile that featured the first internal combustion engine to Carl Benz’s practical automobile that ran on a four-stroke engine. This golden age was awash with inventions that aimed to bring humanity to a new dawn of propulsion, a revolution that would finally have steam engines, horses, and carriages take a back seat. It's in the midst of all this creative energy that led Gottlieb Daimler and Wilhelm Maybach to improve Nikolaus Otto’s internal combustion engine, creating a prototype of modern gasoline engines.

A lot happened in the early years of the 20th century, from wars to geopolitical tensions followed by global industrial growth when the dust from wars settled. It's in the midst of these that the rotary engine was born. And Mazda with an interest to stand out and save themselves from being merged with giant Japanese automakers in 1962, adopted the Wankel rotary engine at its early development stages. The beginning of the Mazda Wankel rotary engine wasn't all-rosy but by the end of the century, every car enthusiast knew the engine by its name. Regarded as one of the most iconic engines that dared to challenge the piston engine, here are ten things you need to know about the Mazda Wankel rotary engine.

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The mind-boggling story of Mazda’s rotary engine began as the dream of a then-young German Felix Wankel. In 1919, 17-year-old Wankel had dreamt of inventing a new type of gasoline engine. With no prior engineering knowledge of how internal combustion engines work, Wankel was on the path to chase his dream. The goal was to create a simple engine that would complete all stages of internal combustion, intake, compression, combustion, and exhaust.

However, it was not until decades later that Wankel would realize his dream while working for NSU Motorenwerke. By 1959, a working rotary engine prototype was completed and several car manufacturers showed interest in the new invention. Mazda's then-president, Tsuneji Matsuda, was at the forefront of acquiring this new propulsion technology to allow Mazda to stay ahead of the game in adopting the rotary and therefore stay competitive. Mazda later signed a contract with NSU to begin developing a Wankel rotary engine for commercial production.

The Mazda Wankel rotary engine completes all stages of internal combustion just like a standard piston engine but with a different angle. To understand its working principle, it’s essential to get attuned to the parts of a rotary engine that work in parallel to the piston engine. Instead of pistons, the Wankel engine uses triangular-shaped rotors mounted onto an eccentric shaft and unlike the piston engine where air is compressed in cylinders, it has a rotor housing instead.

At the start of the cycle, the rotor creates a void that allows air and fuel mixture into the housing, this mixture is then compressed before being ignited by two spark plugs at the combustion phase. The explosion causes the rotor to move due to the expansion of the chamber and at the end of the cycle, exhaust gases are squeezed out of the housing and the cycle repeats.

A simple four-stroke piston engine has at least 40 moving parts, from pistons, connecting rods, and valves to timing gears and the crankshaft. Unlike the piston engine, the rotary engine significantly reduces the number of moving parts, with a single-rotor rotary engine consisting only of two moving parts, the rotor and eccentric shaft. The number of moving parts only rises with the addition of rotors, for example, a two-rotor rotary engine would comprise of three moving parts only, the two rotors and the eccentric shaft.

This simple design is what may have led to most believing that the rotary engine was a revolutionary technology from the beginning. The belief is the reason why Wankel got support from his government in its early development stages and also the reason why the Japanese government supported Mazda in its rotary endeavors, allowing them to work independently.

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After getting the necessary licensing to use and develop a commercial rotary engine, Mazda soon realized that the engine had a major flaw with the apex seals. The vibration of the seals while the rotor was moving made chatter marks in the housing which only derailed commercialization of the engine. However, Mazda’s RE Research Department worked tirelessly to solve this and more issues, leading to the successful creation of the 10A engine.

The success of Mazda’s development of the Wankel engine is what to the production of the Mazda Cosmo Sport in 1967. It was the world’s first mass-production car running on a dual-rotor rotary engine. Its type 10A engine produced a graceful 110 horsepower and that’s how the Cosmo pioneered the commercial success of the rotary engine.

Apart from having few moving engine components, there are also other benefits of the Wankel rotary that made it a formidable opponent of the piston engine. One of them is the compact design. Due to the fact that they need fewer components, Mazda rotary engines are way smaller than their piston counterpart and are therefore less bulky. Their simple and compact design means they can be fitted into smaller vehicles and even motorcycles.

The other major plus of Mazda’s Wankel rotary engine is its quiet and smooth operation. Unlike the piston engine which completes the thermodynamic cycle at 720 degrees, the rotary engine completes it twice as fast, at 360 degrees. This nature combined with the smoothness of the rotor's motion, the rotary engine is capable of achieving incredibly high revolutions, all while having low engine vibrations.

After Mazda had made a name for themselves with the Cosmo Sport, they ventured boldly into the rotary-engine world before but their journey still faced hurdles. First was the Muskie Act of 1970 which aimed to regulate hydrocarbon emissions followed by a fuel crisis. Mazda solved the emissions problem with a thermal reactor system but there was no quick fix for the fuel efficiency issue. This led to them adopting a piston engine alongside the rotary but launching the Phoenix Project to improve their rotary’s fuel efficiency.

The rotary-powered vehicles were now dubbed ‘RX’ and the journey to a successful line of rotary sports cars started with the RX-2. With time, the Phoenix Project significantly solved the fuel efficiency issue, and in 1978, Mazda rolled out the RX-7. It came in three generations from 1978 to 2002, the FB, FC, and the Mazda RX-7 FD, and is the best-selling rotary-powered car ever, with over 811,000 units produced.

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Even in the midst of developmental challenges, Mazda was out to make a name for itself. The RX-7 had proved to be a success even on racing tracks, winning numerous races including the 24 Hours Daytona. Mazda had been competing in the 24 Hours of Le Mans with prototypes since 1974, eyeing a win. The RX-7 FB had managed to finish the race in 1982 but it was not until 1991 that Mazda would finally get the top spot on the podium at Le Mans.

Powered by a four-rotor rotary engine that produced a screaming 700 horsepower, three Mazda 787Bs would power through the finish line at the Le Mans track to bring home a triple crown for Mazda. Finally, after several years of trial and error, Mazda had won one of the most popular endurance races. It would go down in history books as the first Japanese automaker to achieve this fete. Unfortunately, due to some rules, the rotary engine was banned from the race in the preceding years.

From the beginning, automakers soon found out that the Wankel engine had a variety of operational issues. From the chatter marks, dubbed the devil’s nail marks, which would reduce the life of the engine, to the burning of oil inside the housing. Though Mazda’s 47 engineers of the RE Research Department had done amazing work to reduce wear and tear in the housing, the apex seals needed constant lubrication which sometimes resulted in the presence of burnt oil.

The biggest drawback however is fuel efficiency, which is one of the reasons Mazda had to offer a piston engine during the energy crisis of the early 70s. The rotary engine features a long combustion chamber and due to the low compression ratio, they have lower thermal efficiency. This in turn leads to high fuel consumption since the air and fuel mixture isn't completely burned by the last stage of the cycle which also results in constant backfires.

Since Mazda adopted the Wankel rotary, many automakers had tried their hand and given up on the technology altogether. Mazda, however, armed with a team of dedicated engineers that worked to keep Tsuneji Matsuda’s initial goal for the rotary alive, soldiered on. The whole project was seen as a waste of money even within Mazda but with the continuous development of solutions, the engine survived.

Mazda was tenacious in the technology but with stricter regulations on emissions in the U.S. and other major markets, production of the rotary-powered RX-8 was discontinued in 2012. Despite running on a new RENESIS 13B engine, the Mazda RX-8 was not as successful as the RX-7, with only about 200,000 units produced from 2003 to 2012. The project was put to rest with Mazda probably studying ways to use or improve the technology.

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Over the years, the rotary engine has built a loyal following and Mazda refuses to let its dream die. And even though production of rotary-powered vehicles was halted, Mazda still continued to produce 13B rotary engines, passing the art to its next generation of Takumi engineers. On January 2023, Mazda premiered the MX-30 e-Skyactiv R-EV which featured a rotary engine. However, the rotary engine only acts as a range extender for the fully-electric MX-30.

And while the MX-30 is not directly powered by the rotary engine, we can’t say the same for the concept Mazda RX-9. Leaked patents indicate that the RX-9 may feature a tri-rotor rotary engine and an electric motor. So it’s expected that it could roll out as a hybrid, but for now, only time will tell.

Kennedy is not just another writer. Since the early 2000s, before televisions were a thing in every household, he enjoyed his dad's stories of the Safari Rally cars. He finally got a chance to attend the event in 2002 and this was the start of the love for speed, adventure, and automobiles. All in all, besides being a car enthusiast, he is a writer by profession and somewhat a hodophile.