A Brief History of the Rotary Engine

In 1951, German engineer Felix Wankel began development of a completely new type of engine at NSU Motorenwerke.

The first rotary engine concept was unveiled in 1954. Early development was highly controversial as Hanns Dieter Paschke, another NSU engineer, designed and developed his own engine in 1957, the ‘KKM 57’ which was closely modelled on Felix Wankels (without the knowledge of Felix Wankel) who upon finding out, remarked “You have turned my race horse into a plow mare”. The first working prototype, the DKM 54, was fired-up and started on 1st February 1957 at the NSU Research & Development Department Versuchsabteilung TX in Germany. It produced 21 horsepower and unlike modern Wankel engines, both the rotor and the housing rotated. In 1960 NSU and the US firm Curtiss-Wright signed an agreement where NSU would concentrate on the development of low and medium powered Wankel engines and Curtiss-Wright would develop high powered Wankel engines (including engines for aircraft) building on decades of previous Curtiss-Wright design and production experience. Curtiss-Wright went on to pioneer improvements in basic engine design, starting in 1959. Considerable effort went into designing rotary engines in the 1950s and 1960s. They were of particular interest because not only were they were smooth and quiet running but also because of their reliability too which came as a result of their simplicity… and it wasn’t long before others wanted in on them too! Among the first manufacturers to sign licensing agreements to develop Wankel engines were Alfa Romeo, American Motors, Citroen, Ford, General Motors, Mercedes-Benz, Nissan, Porsche, Rolls-Royce, Suzuki, and Toyota. In Britain, Rolls-Royce Motor Car Division pioneered a two-stage diesel version of the Wankel engine in 1960 and Norton Motorcycles developed their own Wankel rotary engine based on the Sachs air-cooled Wankel that powered the DKW/Hercules W-2000 motorcycle (previously used and included in their Commander and F1 motorcylces). Developments continued and ran parallel across a number of different countries;

Mazda first showed an early and sustained interest in the development of the Wankel engine in 1959. They signed a study contract with NSU to develop the Wankel engine and competed with them to bring the first Wankel-powered automobile to market. Although Mazda produced an experimental Wankel that same year, NSU was the first to market with a rotary-powered car, their rather sporty, NSU Spider in 1964. Mazda countered swiftly with a display of 2 and 4-rotor Wankel engines at that year’s Tokyo Motor Show. In 1967, NSU began production of a Wankel-engined luxury car, the Ro 80. However, problems with apex seal wear led to frequent engine failure and associated large warranty costs for NSU which curtailed further development of the Wankel engine. Mazda however, claimed to have solved the apex seal problem, and were able to run test engines at high speed for 300 hours without failure. After years of additional development, Mazda’s first Wankel engine car was the 1967 Cosmo 110S with its ‘Type 10a’ engine. The company followed that up with a number of Wankel (or “rotary” in the company’s own terminology) vehicles, including a bus and a pickup truck. Customers often cited the cars’ smoothness of operation. Mazda opted to run with a method which complied with hydrocarbon emission standards that, while less expensive to produce, increased fuel consumption and just before a sharp rise in fuel prices too. After this Mazda began building cars equipped with both piston and rotary engines. The rotary engine variants were all dubbed ‘RX’ outside of Japan and is the name that we all associate with the rotary engine today. Aside from the family of RX vehicles Mazda also produced a string of grand touring coupe’s branded the Mazda Cosmo; each fitted with various forms of the Mazda rotary engine between 1967 and 1995. The first ‘mass produced car’ after the success of the Mazda Cosmo 110s was the Mazda R100 released for sale in 1970. It was powered by a similar ‘10a’ style Cosmo engine and produced a healthy 100 BHP. It sold remarkably well until production ceased in 1972. Almost alongside the R100, Mazda produced the first ever ‘RX’ model, the RX-2. Although the RX-2 was basically an option based on the Mazda Capella (called the Capella-rotary in Japan) the vehicle was introduced to the rest of world as the Mazda RX-2. The RX-2 sported the first production 1200cc 12a engine with a claimed power rating of 130 BHP and was discontinued in 1974. In 1972 Mazda introduced the RX-3. This model was available as powered by an earlier 10a engine or the larger 12a from the RX-2 depending on the market that bought it in. Also known as the Mazda Savanna, the RX-3 was basically the same but with a different engine, the Mazda Grand Familia and this was produced until mid-1974. 1972 – 1978 saw the birth of the Mazda RX-4, known as the ‘Luce Rotary’ in the Japanese market, it was the first production car available with a 1300cc, 13b engine. The base of all Mazda rotary engines ever since! In late 1978 Mazda introduced the RX-7 FB. The FB was important since it was the first platform designed specifically for the rotary engine which came only with a rotary engine (since 1970’s Cosmo 110s). The Mazda RX-7 FB was refined and re-released across three different series variants. Series-1, released in 1978, continued production until 1980 when Series-2 hit the market between 1981-1983 with Series-3 arriving in the spring of 1984 and produced until 1985. During this time (1978-1985), Mazda sold over 470,000 units making it the best-selling rotary (aka Wankel)-powered vehicle in history. In 1986 Mazda introduce the RX-7 FC, a completely new car aside from its earlier brother in name only, the FB. Despite the many differences between the two models, the two ‘FC’ series’ vehicles produced were named Series-4 (1986-1988) and Series-5 (1989-1991) accordingly, making clear for all to see that the RX-7-FC was a indeed a follow up to the popular FB model. The FC was available with a turbocharged option, the Series-5 ‘Turbo-2’ produced over 200 BHP in this configuration. The FC was also made available as a convertible too. Mazda introduced to the world, in 1990, the 4th instalment of its Cosmo range. The ‘Eunos Cosmo’ was a grand tourer that came fitted as standard with the 13b engine and was also the first factory-produced car available with a 20b engine; a 2 Litre (1962cc) 3-rotor configuration fitted with twin sequential turbo’s. Approximately only three thousand 20b Cosmos’ were ever sold and to this day remain the most expensive and futuristic car that Mazda have ever produced. Unfortunately, perfectly good Cosmo’s are all too frequently stripped and then scrapped for their engines. The factory 20b engine is one of the most sort after of engines in today’s tuning market and is capable of producing over 1000 BHP when heavily modified, a truly remarkable feet of engine engineering. 1991 saw the introduction of what is quite possibly the most famous and definitely the most celebrated rotary vehicle in history, the RX-7 FD. Produced in various forms between 1991 and 2002 the FD is an iconic sports car that really brought the rotary to the masses and made it famous. Ironically in the UK only 124 cars were ever officially sold via Mazda UK, though the coveted UK-spec cars are now far outnumbered by imports from Japan. No one really knows precisely how many FD’s are here in the UK today. By the time FD production stopped in 2002 with the spirit-R (the last RX-7 production model) factory cars were leaving Japanese show rooms with 280+ BHP. Though advances in technology and with the help of years of research & development on the part of enthusiasts and specialists around the world, remarkably, the 1308cc 13b-REW* has been known to produce in excess of 800 BHP and in some cases even in street legal vehicles, 400+ BHP is almost becoming ‘easily’ achievable. As a result however, unmolested RX-7 FD’s are becoming quite a rare commodity.

Explanatory factoid: 1308cc 13b-REW This ‘REW’ suffix stands for ‘Rotary Engine Double-Turbochargers’. As Mazda didn’t want to use the acronym “RED” for “Rotary Engine Double [Turbos]” they opted to use “W” (Double-U) as a compromise, thus the “REW” suffix.

  Then, in 2003, Mazda unveiled their all new rotary powered sports car, the successor to the hugely popular RX-7, the Mazda RX-8! The RX-8 was designed as a front mid-engine, rear-wheel drive four-seat, four-door coupé, with near perfect 50/50 front to rear weight distribution. Front double wish bone suspension with rear multi-link suspension on an all new zero parts carried over chassis. Mazda called their platform ‘the new sports car platform’ and intended on using the revolutionary design as a base for all its future sports cars within the next decade and possibly beyond. True to this, the new MX-5’s are built on this same RX-8 chassis. The ability to produce such a well balanced car came in no small part from being able to build it around the engine. The RX-8 was sold as having an ‘all-new rotary engine’, codenamed Renesis, coined by boffins at Mazda from Rotary-Engine-Genesis. Realistically though the new ‘renesis’ engine shared most of its major components with previous 13b engines, however each part had been completely re-engineered in one form or another. Switching out the traditional peripheral exhaust ports for side exhaust ports to lower emissions and fuel consumption, overcoming the many issues that in itself created, redesigning all associated engine ancillaries to enable realistic power output from a normally aspirated rotary meant that in many ways the renesis engine was just as new as it was ground breaking. The entire naturally aspirated high power renesis engine and ancillaries is a 30% smaller unit than the previous twin turbo 13b-REW unit. JDM RX-8 high power models came out of the factory with a claimed 247 BHP, normally aspirated. The original RX-7 left factories with a claimed 255 BHP with sequential twin turbo’s. The actual power rating of both original road cars has always been speculated, however, to claim the outputs Mazda had to prove them which meant that they must have tested the engine on a dynometer in order to produced those levels of power. Not bad from a road-going rotary, choked by emissions regulations and fuel consumption worries! Unfortunately with diminishing sales and tightening emissions regulations the continued production of the RX-8 had become unfeasible and had to be cut short. UK sales ended in December 2011 and production stopped completely on 30th June 2012, with the last of a 2000 unit limited run of Spirit-R RX-8’s sold only in the Japanese domestic market coming off the production line. With a worldwide production total of just short of 200,000 units the RX-8 should be considered a real success. Whilst it didn’t match the sales of the original RX7 FB (even by half), in today’s market it did do remarkably well. The future of the RX-8 now lies firmly in the hands of the aftermarket, RX-8 specialists and enthusiasts like ourselves. With reliability issues and claims of a lack of power considering its infamous thirst for petrol the future might look a little bleak. More RX-8’s are being sent to the scrap yard at the moment here in the UK than are being maintained and kept on the road, and many of the established aftermarket parts manufacturers have disregarded the RX-8 as being too difficult to modify. Fortunately however, a select few still recognise the potential that the chassis and even engine offer, with firms like Mazda Rotary Parts, Powergains Motorsport, Re-Amemiya and HKS picking up the slack left by larger aftermarket parts manufacturers. We like to think we’re doing our bit too here at Rotary Revs, where not only do we rebuild, repair and maintain many RX-8s on behalf of our customers, but we have also spent considerable time and energy developing our own aftermarket parts and up rating tweaks for your RX-8. Visit our store to check our some of the parts we have on offer!

The Future of The Rotary Engine

It is incredibly difficult task to be asked to speculate on the future of the rotary engine. With so little information coming from of Mazda on the subject, there are still the many rumors that leave that glimmer of hope. What we do know, is that Mazda have been continuing development of another rotary engine dubbed the ‘16x’, although likely in a similar fashion to that which placed the company on the band wagon first time around and yielded results such as the RX-8’s Renesis engine. An original small team of 47 people made the Mazda rotary a reality in the 1960’s. Similarly, in the 1990’s, a group of in-house enthusiasts reportedly developed the Renesis in their own spare time creating the engine that powered the RX-8. Hopefully there’s something like this going on behind the scenes now with the ‘16x’ project. The 16x is, allegedly, an all new rotary with a longer ‘stroke’, rumored to use direct fuel injection and a more advanced ignition system. The new 1600cc 2-rotor rotary engine is thought to be designed to offer higher power outputs and vastly improved fuel economy in order to compete with modern piston engines. As it stands at the moment though, there has been no official confirmation of this or word from Mazda themselves. We are more likely to see the rotary in Mazda vehicles as a range extender on electric motors some time in the future. Other manufacturers such as Audi have been experimenting with the technology too. So who knows, but another ‘RX’ would be very welcome indeed! Petition anyone?

A word from MD, Ben Dunn;

“Personally I’d like to see another dedicated rotary sports car from Mazda by 2017. I’ll certainly be at the front of the queue for it when or if one does! I think I speak for all Rotary enthusiasts when I say we all have our fingers and our toes crossed.”


Update February 2016

Well Ben love’s nothing more than to be right … and guess what. In October 2015 at the Tokyo Motor Show, Mazda unveiled the RX-Vision, the new concept for the next generation of Rotary engine sports car. Obviously in true Mazda style though they aren’t giving too much away just yet but we do know a little.

The new car will be a shout out back to the past. A 2 -door, 2 or 2+2 seater , the same as the RX-7. It’ll be powered by the new generation of rotary currently called the 16x and is likely going to be called RX-7 (FE? FF?) and is aimed to compete with the Porsche Cayman.

We’ll continue to update this article as more information about the RX-Vision comes to light!