A1 e-tron and Audi's Rotary Engine History

Last week, Audi is the latest manufacturer to send a fleet of small electric powered city cars into urban use trial. 20 units of the electric powered Audi A1 e-tron will go on trial in the German city of Munich. Similar to what BMW has done with the MINI-E. However there is an interesting twist to Audi's effort, as the A1 e-tron is a range extended electric vehicle (REV), ala Chevrolet Volt. The A1 e-tron is not only powered by a lithium ion battery pack but it also carries along its own generator to recharge the batteries. The Li-ion battery pack is good for around 50km, after which a the generator kicks in. But again, here is another twist. Instead of a small conventional piston engine like the Chevy Volt the Audi uses a single rotor rotary engine. Anyway as usual, this blog is not interested in repeating what is already available in the press release, which can be found here.


The interesting thing is Audi's decision to use a Wankel rotary engine instead of a regular small 3-cylinder 4-stroke piston engine, the default option for most manufacturers. Conceptually it may be purely a technical decision due to the packaging benefits of a compact Wankel rotary engine. It certainly suits a small car like the A1.


Mazda have shut all debates about reliability of rotary engines by winning the 1991 24 Hours of Le Mans in the Mazda 787, the only Japanese manufacturer to ever win a Le Mans and also the only and the last rotary engine car to win Le Mans as FIA have since banned entries of rotary engine cars. It was a political decision but that's another story. However the challenge still remains that it cost a lot more to maintain a rotary engine and it requires pretty exotic materials in its manufacture. Not to mention that rotary engines use a lot more fuel than a comparable reciprocating piston engine of similar output.

So the question remains, why choose a rotary engine? Even Mazda, the rotary engine evangelist wisely only fit its niche models like the RX-8 with a rotary. The company have wisely backed down from its earlier plans to fit rotary engines on a wide range of its high volume cars. Plus Mazda have significantly backed down from its previous rotary evangelist stance in the 80s and instead choose to focus more on its Zoom-Zoom philosophy in its marketing. Could it be possible Audi sees the short operating period of the rotary engine in a range extender EV will off-set a lot of the disadvantages of a rotary? But still, the logic doesn't sound very convincing, either on a technical or a commercial view. Interest in rotary engines peaked in the 70s but since then all manufacturer except Mazda (which cultivates a quirky but innovate brand image so rotary still have some value to the company) have since abandoned the concept. GM tried the Corvette XP series concept, Mercedes tried the C111 Concept and both have since abandoned the technology.

Mercedes-Benz C111 rotary engine concept, 1969


Chevrolet Corvette XP rotary engine concept, 1973

We later found out that the rotary range extender engine not developed by Audi, but by an Austrian engineering consultant called AVL. AVL is offering a compact packaging hybrid solution to OEMs with its rotary range extender, and choose to work with Audi to showcase the concept. Most people associate rotary engine technology with Mazda, but truth is that the first mass produced rotary engine car was produced by Audi, or more accurately, the NSU brand which was part of the greater Auto Union, the forerunner of the present day Audi.

In the 1936, Felix Wankel was a self-thought engineer who never went to college. He was 22-years old when he invented the rotary engine concept. What were you doing when you were 22?! By the 1950s, Felix Wankel convinced NSU to support his invention. The first working rotary engine was started on a NSU test rig in 1957.

The origin of NSU can be traced back to 1873, founded by Christian Schmidt and Heinrich Stoll was a knitting machine manufacturer. NSU is short for Neckarsulm, NSU's founding city. The origin of NSU reminds me of Toyota - both started as knitting / fabric machineries maker. Like Peugeot, NSU began expanding to manufacture bicycles when the bicycle boom started. When the motorcar was invented, NSU was played a critical role at this turning point of history. The little known fact was that NSU was the one who built Gottileb Daimler and his technical partner Wilhelm Maybach's Stahlradwagen (steel-wheeled car) chassis.


NSU would later go into motorcycle manufacturing (like BMW) and go on to become the largest two-wheeler manufacturer in the world and largest motorcycle maker in Germany.
NSU bikes

In 1963, NSU showed the single rotor NSU/Wankel Spider to the public for the first time at the Frankfurt Motor Show. The car went on sale a year later. Mazda would release its first production rotary engine car, the Cosmo in 1967. By 1968, NSU released its second rotary engine model, this time a high volume large sedan called Ro 80. Initial impression of the car was so good that it was voted the 1968 Car of the Year.

NSU/Wankel Spider



NSU Ro 80


Mazda Cosmo

However problems began to surface almost as quickly. It soon became apparent that there were serious design flaw with the engine, mainly caused by insufficient field testing and the choice of rotor tip material was not suitable. Problems began to appear by 15,000km and some engines required complete rebuild by 50,000km. The problem was eventually solved but the financial woes suffered by NSU was already too serious to correct. NSU was a relatively small company to begin with, and have even less resources to do the sort of development work required to refine the rotary concept. NSU could not weather the financial storm well and the Dresdner Bank, NSU's main shareholder urged NSU to find a larger partner. Eventually VW would take over NSU in 1969 and the company was merged with VW's subsidiary Auto Union GmbH, to form Audi NSU Auto Union AG.

Decades earlier, Auto Union was devastated after World War 2 as most of its production facilities was located in the now separated East Germany. BMW suffered a similar fate but Daimler-Benz was lucky to avoid this fate. In the post-war years, Daimler-Benz wanted to enter the lower segment market. Pouring huge capital in uncertain economic time to develop a new model is risky so Daimler-Benz purchased Auto-Union GmbH and the company's DKW Junior model was doing brisk sales for Daimler-Benz.

DKW Junior

However the good news didn't last long. Mercedes customers weren't too happy that their cars are associated with the humble DKW from Auto Union. Daimler-Benz received its first lesson in managing a multi-brand model line-up. Daimler's board was afraid of losing their core customer base. At the same time, Daimler-Benz's truck operations, which was quite profitable but its existing plants in Mannheim and Gaggenau was in urgent need of expansion. Daimler was offered an opportunity to purchase a new plant at Rhine but didn't have the finances to secure it. Daimler then decided to sell Auto-Union GmbH to Volkswagen by 1966 to raise funds. Out of the deal, VW got the DKW F102 developed largely with Mercedes fund. VW also decided that all Auto Union cars from this point onwards will be sold as an Audi.

DKW F102
It was only in 1985 that Audi NSU Auto Union AG was renamed to Audi AG, matching the brand and the company name as a single concept. This was not an easy task due to historical legacy. Auto Union was formed in the difficult post-Great Depression years with the merger of Audi, DKW, Horch, Wanderer and later NSU. Ironically, 30 year later Audi would return to pose a strong challenge to Mercedes, the company that once owned Audi.

It should also be mentioned that Audi did preserve much of NSU's heritage. The original NSU plant is now one of Audi's flagship plant. The Neckarslum plant makes Audi's flagship cars like the R8 supercar as well as the A8 sedan. It is also the one of the few car plants in the world that can weld aluminium.

Audi A8 with aluminium space frame technology and NSU TT, NSU Ro 80 in the background.