- The rotary engine invented by Felix Wankel quickly became a Japanese icon and attracted the attention of various automakers around the world.
- Mazda has been the most successful in commercializing the rotary engine and produced famous models such as the RX-7 and RX-8.
- While a pure rotary-drive model seems unlikely due to emissions regulations, Mazda may be working on a rotary-drive hybrid sports coupe known as the RX-9.
Over the past 140-odd years, the automotive world has seen many different types of engines. From the humble steam engine powering one wheel, to the massive turbocharged W16 four-cylinder powering one of the fastest cars on the planet, and everything in between.
While piston engines in all configurations have pretty much held a monopoly in the internal combustion world, there is another type of engine that was originally a good idea and quickly became a Japanese icon – even if the engine itself was German-designed.
Enter the rotary engine, a pistonless engine that uses spinning Doritos to propel a car. It was a brilliant idea that ran between 1967 and 2002 before getting the ax from Mazda. Although the rotary engine has received praise from all over the world, we still think it is an underrated engine.
History of the rotary engine
The rotary engine was first invented by Felix Wankel back in the 1920s and patented in 1934. Not only did he create a prototype of it, but he also proved that it could work as a car engine. The design was made commercially feasible by Hanns-Dieter Paschke. With the help of Otmar Bayer of the Stuttgart University of Applied Sciences, Wankel got the German automaker NSU to start developing a rotor for use in their motorcycles.
The NSU Spider was the first car to use a Wankel engine, and soon many other companies were requesting licenses to produce their own versions based on the Wankel patent. Among the companies that received licenses were John Deere, Daimler-Benz, MAN, Krupp, Alfa Romeo, Rolls-Royce, Porsche, Nissan, Suzuki, General Motors, Toyota, Ford, Yamaha, Kawasaki, American Motors and many others. However, the most important company was Toyo Kogyo, which would later be known as Mazda.
Today, many of these manufacturers have concept cars with rotary engines, one of the most famous is the Mercedes-Benz C111 which was a light sports car. The C111 had a 4-rotor engine with a displacement of 2.4 liters and produced 345 hp. and 289 lb.-ft.
Another famous rotary concept car was the Chevrolet XP-895, also known as the Aerovette. Zora Arkus-Duntov conceived the idea of a mid-engined Corvette back in the 1960s, and by the late 1970s the Aerovette was a working prototype with a 4-rotor rotary engine. The rotary engine was eventually replaced by a 6.6-liter V8. as we know A mid-engined Corvette won’t arrive until 2020 – almost 50 years after it was conceived.
Although many automakers tried their hand at creating a model with a rotary engine, only Mazda managed to achieve commercial success with the engine. Granted, keeping a rotary engine running for long periods of time requires money and patience, but the engine holds a special place in the minds of enthusiasts.
The era of Mazda
Mazda’s first car with a rotary engine was the Cosmo 110S of 1967 – a sports car with a capacity of about 110 hp. The Cosmo was powered by a 0.982 liter twin-rotor engine and remained in production until 1972, when it was replaced by the new Cosmo in 1975. The second generation Cosmo was also sold globally as the Mazda RX-5.
At the same time, Mazda began production of RX cars, and the RX-2 appeared in 1970 under the name Capella, known in Japan as the Capella Rotary. The RX-3 appeared in 1971, and since then RX cars have continued to gain popularity. Mazda offered traditional piston engines in all of its RX cars, but dropped the option for the RX-7 in 1978.
The Mazda Cosmo continued to offer inline engines until 1989 as these cars were used for official reasons, but in 1990 piston engines were dropped for the last generation Cosmo. This version of Cosmo was was called Eunos Cosmo and was a better alternative to the German GT. The Eunos Cosmo even got an optional three-rotor version called the 20B and produced 276 hp.
However, the most famous of the rotary engines was the 13B. It began life in the second generation Cosmo in 1975 and lasted until 2002 – with improvements, of course.
13B-REW in RX-7
The 13B-REW was the second-to-last iteration of Mazda’s now-legendary rotary engine, which was used to power the last-generation RX-7. It was a twin-rotor design that used sequential turbochargers for the extra boost needed for competitiveness.
During the ten years of production of the latest generation, Mazda made minor changes to the engine and tuning, increasing the 255 hp. in the model 1992-1995 RX-7 up to 265 hp. in the 1996-1998 model. The model got better and better, and by the late 1990s and early 2000s, Mazda was producing 276 hp. with the same setup.
The official output stopped there, as the Japanese automakers made their gentleman’s agreement that no car exceeded the 276 hp mark. – just like the German manufacturers with a speed limit of 155 mph. By 2002, the Gentlemen’s Agreement was largely ignored, and sports car power quickly climbed to the 300 hp mark. and above Mazda couldn’t really keep up with their rotors and so dropped out of the competition.
Instead of continuing the legacy of the RX-7, Mazda built the RX-8, a strange mix of sports car and grand tourer. It was introducing a new and greatly improved version of the 13B called RENESIS. RENESIS absorbed everything gained from more than 30 years of experience, but abandoned turbochargers for the naturally aspirated version of the engine.
The RENESIS is built around the 13B-MSP (Multi-Side Port) and has better airflow to help improve fuel economy and engine efficiency. The engine produced slightly less power than the twin-turbo version in the RX-7, but with noticeably better reliability. Reworked exhaust ports provided better combustion accuracy, and the rotors received better seals and low apex seals on the Dorito corners, creating less friction and bringing the engine closer to its potential.
The overall result of this upgrade was that the RENESIS achieved 49% higher power and fuel economy than the conventional 13B-REW. Mazda has also changed the scope of work for awards and releases. The RENESIS still only had two rotors with a volume of 0.654 liters, but the two combustion cycles gave it a displacement of 2.6 liters instead of the standard 1.3 liters.
The future of the rotary engine
Mazda ended production of its rotary engines in 2012 when the final RX-8 rolled off the assembly line. Since then, the automotive community has been anxiously waiting to see if the engine will be restored. Unfortunately, in this day and age of emissions and fuel economy regulations, a new rotary-only model seems unlikely.
Mazda did present the RX-Vision Concept back in 2015, but so far nothing has come of it. The Japanese company has been seen filing various patents for a rotary-drive hybrid sports coupe that may or may not be the RX-9. It is also possible that Mazda is working with Astron Aerospace to use their Omega 1 engine as a new rotary engine.
This is all speculation as Mazda has not confirmed anything. They introduce new engines – surprisingly – such as the new turbocharged inline-6 in the CX-90 SUV, and the engine is rumored to find its way into the BMW 3 Series sedan.
As for the future of the rotary engine, if there’s any company that could make it a reality again, it would be Mazda. We’ll just have to wait a little longer.