The History of the Rotary Engine
The rotary-engine (also known as the Wankel-engine) is an alternative to the classic piston-engine, developed in 1954 by the German mechanical engineer Felix Heinrich Wankel.
Wankel’s main motivation was to create an engine that wouldn’t have the strong vibrations of a piston engine.
While the engine he constructed worked just fine, it wouldn’t find its way into cars until after NSU’s engineer Hanns Dieter Paschke reworked it two years later in order to make it cheaper to mass-produce.
Because of that all rotary engines you can find in cars will be based off Paschke’s design, called “KKM 57P” rather than Wankel’s “DKM54”.
How the Engine works
The rotary engine consists of an oval chamber (comparable to the cylinder of a piston-engine), with a spinning rotor inside of it, moving off-center on a (usually horizontal) axle running through the middle of the chamber.
The rotor has the shape of a Reuleaux triangle with flatter sides, simply put a rounded triangle.
Due to the off-center rotation the rotor creates three separate sections within the chamber, the sum of which is the engine’s displacement.
At first the fuel-air-mixture is injected into the first section, from where the spinning rotor transports it around (compressing it in the process) to the ignition section, where a spark plug (on modern rotary engines two spark plugs) ignite the mixture, pushing the rotor onwards.
The continued motion of the rotor pushes the burnt gasses back around towards the intake, but they’re disposed of towards the exhaust before they can reach the intake-section.
Advantages & Disadvantages
Apart from the drastically reduced vibrations the rotary engine has a few more advantages compared to classic piston-engines:
-It has only two moving parts, the rotor and the axle
-Vibrations can be pretty much eliminated with well-balanced counterweights
-A comparable piston-engine would be 3x as heavy and 3x as large
-Rotary-engines are unlikely to suffer early self-ignition (“knocking”)
-Higher revolutions per minute are manageable
The engine does have disadvantages too, among them:
-Extreme temperature-differences within one chamber lead to short-lived seals
-Usually less torque than comparable piston engines
-Impractically shaped ignition-section, leading to poor efficiency
-Multi-rotor engines are prone to heat-damage in between the chambers
-Oil injected into the chamber for lubrication and seal-preservation leads to high oil-consumption and poor emissions-standards, especially notable with Mazda’s “13B”-engine.
The Diesel Wankel - A brief excursion that led nowhere
In the 1970s Rolls Royce developed a diesel-version of the rotary engine for a planned British tank, but development was stopped just before the engine was finished when the tank was no longer needed.
The diesel-rotary used one rotor inside another moving slightly “ahead” to enable higher compression.
But even with the much more complicated system used (which I didn’t manage to figure out clearly enough to write here) the engine didn’t work nearly as efficiently as desired.
Maico worked on a diesel-Wankel for motorbikes in the mid-1990s without a result, before Pats Aircraft finally had success and put a working diesel-Wankel on sale in the late 1990s/early 2000s as an auxiliary power unit.
The engine wasn’t sold for long, and while usage as an APU is possible the emissions never got nearly good enough to consider a diesel-Wankel for a car.
At the same time the Wankel Rotary GmbH kept working on a diesel-Wankel for a car, introducing direct injection and spark plugs in order to finally get the concept to work.
However, the company failed to present a working engine fit for mass-production before the company filed for bankruptcy in early 2001.
With emissions being more important than ever, and the rotary being not very common anymore in the new millennium, it is unlikely that there will be a diesel-Wankel anytime soon.
The Birth of the Rotary Car - And the Czechs did it
Contrary to popular belief it wasn’t NSU or Mazda who first dumped a rotary-engine under the hood of a car, it was Skoda.
An unknown number of 1000 MBs was fitted with single-rotor rotary engines in the early 1960’s and used for experimental purposes.
The cars were never sold to customers, and after the end of the experiments they were most likely scrapped.
The NSU Wankel Spider - Getting the Wankel into Mass Production
The Wankel Spider, made by the German car manufacturer NSU (later became part of Audi) was the first production-car to be fitted with a rotary-engine.
The 700kg light two-seater convertible carried a 497,5ccm single-rotor rotary engine in the rear, delivering 37kw at 6000 rpm (customers could chose a “sports package” for 48kw, 10 of which were sold).
To counter the engines weight the fuel-tank and radiator went into the front, leaving two tiny luggage-compartments.
The engine was powerful enough to push the car to 155 kph, not at all a bad top speed for the time.
2.375 cars were made, about two-thirds are said to be still around.
The Curtiss-Wright Mustang - A Rotary-Powered Muscle Car
In 1965 the American company Curtiss-Wright presented a Mustang which they had fitted with a massive 3.932ccm twin-rotor rotary engine, basically two enlarged license-build NSU-engines mounted together.
The engine put out 138kw at 5.000 rpm, easily enough to make the Mustang move appropriately.
When the car failed to generate the desired positive feedback (which is understandable) Curtiss sold the rights to the NSU-engine, making the red Mustang the only car with a US-made rotary engine.
It changed hands a few times, the last information placing it in “The National Automotive and Truck Museum of the United States” in Auburn, Indiana in 2012.
So I guess us car guys shouldn’t be upset about V8-fitted RX7s, because after all that swap was done the opposite way first.
The Mazda Cosmo - The Japanese enter the Rotary-World
When Mazda unveiled the Cosmo (called the 110S for export) in 1967 they became the first company to sell a mass-produced car with a twin-rotor rotary engine.
It is somewhat ironic that they beat NSU’s Ro 80 by a few days, unveiling a car powered by a license-built version of the Ro 80’s engine.
The engine in the Cosmo had a displacement of 982ccm (2x491ccm) and produced 81kw, with the engine’s small size allowing a very aerodynamic design.
The name Cosmo was meant to remind customers of the “space race”, supposedly making the car appear very futuristic.
Nowadays the Cosmo is highly sought-after, with decent survivors having recently reached average prices of 100.000$.
The NSU Ro 80 - The Germans catch up
Shortly after Mazda unveiled the Cosmo NSU started selling the Ro 80, a 4-seater sedan for the upper middle class (comparable to today’s Audi A6 and Mercedes E-Class).
The engine is identical to the Cosmo, putting out just 4kw more due to different carburettors.
Many customers chose the Ro 80 for its low interior noise, modern design and/or because they wanted to drive an innovative car without having to trust an Asian car (which, by the way, was never made in left-hand-drive).
However, the Ro 80 soon got bad publicity, with engine failures due to failing apex-seals happening as soon as a week after the customer purchased the car.
That engine-trouble is why there were almost twice as many engines made as there were Ro 80s made, and only 4 “matching numbers”-cars being known (two of which went straight to museums).
Despite the fact that it is a very special car prices have remained rather low, partly because many oldtimer-fans don’t like the car for looking too modern for a car from around 1970.
Pininfarina presented a potential successor, the “Ro 80 2 Porte +2” as early as 1971, but NSU decided to retire the rotary engine when the Ro 80 stopped production in 1976.
The Mazda R100 - The Cosmo's practical Sibling
Wanting to sell rotary engines to a larger audience Mazda took the Mazda 1000/1300 (called the “Familia” in Japan), and fitted it with the Cosmo’s engine, simplified by using only one carburettor, reducing the output to 74kw.
The result was sold as the “Mazda Familia Presto Rotary” within Japan and as the R100 in a few European countries (including France and the UK) as well as the USA (with round rather than rectangular headlights).
The 982ccm rotary was widely liked in Japan, since owners of cars with under 1000ccm of displacement had to pay far less taxes.
That led to a few other Mazda-cars getting sold with the rotary engine as an optional equipment in the following years.
The Citroën M35 - The French Experiment
Not wanting to miss out on the market for the innovative engine Citroën presented the M35 in 1969.
The car was based off the Ami 8, but fitted with hydropneumatic suspension and its own body.
The only parts “off the shelf” were the front fenders, the front indicators, the lights and the steering wheel.
The engine was, simply put, half the engine from the NSU Ro 80, producing 36kw from 497.5ccm of displacement in a single chamber.
Originally Citroën and NSU had planned to produce rotary-engines together under the name “Comotor”, but Citroën failed to finish the factory in time leading to NSU sending partly assembled engines from their factory in Neckarsulm, Germany.
Instead of a normal production Citroën planned to have long-time customers apply to be allowed to buy one of just 500 M35s.
Customers were less eager than expected, though, and only 267 M35 were made.
Over the next two years Citroën collected data during routine inspections, before planning to buy the cars back for what the customers originally paid, in order to get some more information before scrapping the cars to avoid having to provide spare-parts.
Six M35s are said to have survived Citroën’s attempt to get them back and have them scrapped, with rumors saying that one was destroyed in Germany a few years ago when the warehouse it was stored in was torched and burned down.
The Mercedes-Benz C111 V1 - The SLS that never was
Just like Citroën Mercedes didn’t want to miss out on the “Wankel trend”, unveiling the Mercedes-Benz C111 Version 1 at the 1969’ IAA in Frankfurt, Germany.
In the months before the presentation journalists had repeatedly managed to take photos of a mysterious Mercedes-made supercar with gull-wing doors reminiscent of the famous 300SL.
The C111 Version 1 was a 1.125mm low two-seater supercar consisting of a welded steel-base carrying the drivetrain, fuel-tanks, interior and a rollcage, with a riveted-on glass fibre reinforced plastic body.
The gull-wing doors were necessary due to two fuel-tanks in the flanks, which supplied a triple-rotor rotary engine that made 206kw from 1800ccm (3x600ccm), enough to push the car to a confirmed 262kph.
Despite potential customers sending blank checks to Mercedes, wanting to buy whatever production-car they would turn the C111 into.
But Mercedes denied all offers.
The triple-rotor rotary was disliked for delivering too little torque, a later fitted quad-rotor rotary wasn’t reliable enough.
The plastic body, made for Mercedes by a company specializing in railway-cars, caused problems too, being said to have never reached the quality-standard Mercedes expected from a car carrying their badge.
Mercedes eventually “changed their aim” to turbo-diesel engines, running tests without any indication of planning a road-going car.
The Chevrolet Corvette XP-897GT - A Car Chevrolet wants you to Forget
Eight years after the Curtiss-Mustang another American car with a rotary-engine was unveiled at the 1973 IAA in Frankfurt, Germany.
The Chevrolet Corvette XP-897GT (because why use a simple name) is a very interesting car, mainly because it is mostly not a Corvette.
The car was powered by a huge Chevrolet-made 4.359ccm twin-rotor rotary mounted behind the seats, sending 134kw to an automated gearbox at the rear, developed for the upcoming 1980’ Chevrolet (“X-Body”) Citation.
The car was built within six months by Pininfarina, using a Porsche 914’s chassis.
While the design was meant to show where future Corvette-generations were going, it is unknown if Chevrolet was serious about the rotary-engine of if that was just “something special” for the show car.
After the IAA the car disappeared, before it was assumed to be lost in a fire in California in 1977.
It reappeared when a gentleman called Tom Falconer got a call from a friend in 1982, saying he spotted “a strange Corvette” at a scrap yard.
It turned out Chevrolet had “made the car disappear”, wanting to erase any trace of having ever had a Wankel in the beloved V8-powered car, or a mid-engined Corvette.
Mister Falconer first restored the car in the silver paint-job it had received since its presentation, fitting a Vauxhall Cavalier’s engine just to get the car moving, before fitting a Mazda 13B rotary engine (the engine first used in the Cosmo), a Cadillac automatic gearbox meant for FWD-cars, and applying a new paint-coat in the original Candy-Apple Red in 1997.
The car, then looking the way you see it above, was still owned and driven by Mister Falconer in 2010, which is the latest reliable status.
The Citroën GS Birotor - A Failure as the Result of an Experiment
Based off the information gained from the M35 a few years before Citroën presented the Citroën GS Birotor in 1973.
The car largely resembled the normal piston-engined GS, save for a few details and, of course, the drivetrain.
The engine, made by the company “Comotor” (see the M35’s entry for information) is a reworked version of the NSU Ro 80’s engine, a twin-rotor rotary engine producing 77kw from 995ccm.
The car also featured a much better standard equipment compared to the normal GS, as well as five-bolt rather than three-bolt wheels, disc-brakes all around and a three-speed semi-automatic gearbox.
Somewhat unfortunately, the car was expensive (costing more than the much larger Citroën DS) and went on sale just when the 1973 oil crisis hit.
Instead of thousands of cars only 847 units were sold before Citroën retired the model in 1975, attempting to (once again) buy back all the cars.
This time, it is reported that Citroën was so eager to get the cars off the streets that they even offered more money than the cars had originally cost.
Depending on which source you chose 4-7 Birotors exist today, which, for decades, couldn’t be sold since there was no title for them, along with other missing paperwork.
As far as Citroën was concerned, the car didn’t exist, and a car that doesn’t exist can’t be sold.
The Mazda Rotary Pickup - An interesting Oddball
Obviously ignoring one of the most important features of pickup-trucks Mazda presented the Rotary Pickup, based off the second-generation Mazda B-Series, in 1974.
Somewhat strangely, the car was apparently only offered in the USA and Canada.
The 2650mm long pickup can be visually distinguished from the piston-engined versions by flared fenders, the battery having been relocated to a position under the bed, a different dashboard and front grille as well as round taillights.
The original tailgate also had “ROTARY POWER” written across it with tape.
The car uses the 13B engine known from the Mazda Cosmo with two rotors adding up to 1308ccm producing 82kw and 158 newton meters of torque.
Road & Track was impressed with the car’s “smooth, quiet power” and nice interior, but, like many, criticised limited torque.
The car appeared in the showrooms in 1974, with prices starting at about 3.500$ (about 16.800$ in today’s money).
Due to the energy-crises cars sold badly at first, and Mazda had dealerships return unsold 1974’ cars.
They were re-stamped with an “S” in the VIN-number, designating them as 1975’ models, before going back to the dealerships.
The car ran from 1974 to 1977, with a subtle facelift for the last year, selling just over 15.000 times.
Larger success was probably limited by the unusual (and not very reliable) engine as well as a lot of people preferring an American over an Asian car out of tradition.
A small number of cars survived, and good examples are very sought-after by enthusiasts.
The Mazda Parkway - The Rotary trying to be too practical
Continuing their tradition to stick a rotary engine in everything they could get their hands on for long enough Mazda Presented the Parkway in 1974.
The 25-seats minibus (plus one driver) was driven by an enlarged version of the 13B-engine, producing 100kw and 179 newton meters of torque.
Since the engine (which was mounted mid-ships under the floor, driving the rear wheels) was struggling with the 2885kg of bus (with things getting worse as soon as passengers were on-board) a conventional 1000ccm piston-engine was placed behind the rear axle to power the air condition and electrical systems.
The poor performance paired with the high fuel-consumption led to the bus not being very successful, being only sold 44 times from 1974 to 1976.
About a third of the busses are said to be still in working condition, and usually get inherited rather than sold.
The Hercules W 2000 - The Rotary goes motorbiking
1974 also saw the rotary find its way into mass-production bikes, with the German company Hercules presenting the W 2000.
The bike was powered by a single-rotor rotary engine that produced 20kw from 294ccm (a scaled down license-built NSU-engine), with the engine driving the 176kg heavy bike through a 6-speed manual gearbox.
Hercules rushed the bike into production in order to beat Suzuki, Honda, Yamaha and MZ, paying for that with poor quality in early bikes.
Hercules was the first company to sell a rotary bike in most of the world, with only the US-market getting the Suzuki RE5 first.
The bike (nicknamed the “hoover” due to the large radiator in front of the engine) wasn’t very successful through its 5-year run, partly because of the poor quality and partly because of the high price (prices started at 4550 German Mark, almost twice as much as the competition).
The poor sales, combined with Hercules producing bikes even without orders, led to some of the 1.800 W 2000s made surviving past the year 2000 without ever being registered.
Needless to say that those “sleeping beauties” are the most expensive ones today.
The Mazda Road Pacer AP - The Australian-Asian Rotary
Mazda’s next notable rotary-powered car was the 1974 Mazda Road Pacer AP, and it’s mainly notable for not being a Mazda.
Mazda was looking for a new sedan for the upper middle class, and wanting to cut down costs they partnered with GM’s Australian company Holden.
Holden would build Holden Premiers in Australia, and then ship the complete (but engine-less) cars to Japan.
Mazda installed their trusty 13B rotary engine under the hood, delivering 1308ccm from two chambers.
While the low noise and smooth power delivery were praised the engine had to fight to get the 1600kg heavy car moving, leading to slow acceleration and a fuel consumption as poor as 8.5 miles to the gallon.
The car came with heaps of standard equipment, but still sold very poorly (with the oil-crisis not exactly helping), leading to only 799 cars being sold in 5 years.
The Audi 100 C2 Wankel - A Ro 80-Successor that did not happen
While NSU had retired the rotary-engine with the end of the Ro 80 their “successor” Audi (back then called the “Audi NSU Auto Union AG”) kept experimenting, fitting 25 Audi 100 C2 with a 132kw twin-rotor rotary-engine (based off the Ro 80’s engine) for a 1977 fleet-experiment.
While the cars were well-liked the engines were disliked, and needed and absurd amount of oil (helping to create the term “head to the fuel-station, check the fuel-level, refill the oil-tank”).
23 of the cars were scrapped, with one being owned by the “Autostadt” museum in Wolfsburg, Germany and one being lost over time.
The Mazda RX-7 - The JDM-Legend
I have no doubt that most of you reading this know this car, and some probably love the third generation of it which appeared in 1991.
The RX-7 (called the Savanna in Japan) rolled into the showrooms in 1978, just when the era of the rotary engine seemed to be over.
With Audi’s experiment failing there no longer was a car with the NSU-pattern engine around, which made Mazda the only producer of a rotary-engine.
They insisted on calling it that rather than a “Wankel”, since the name-rights to the Wankel were owned by Volkswagen.
The twin-rotor engine developed 95.5kw and 167 newton meters from 1.148ccm.
Mazda’s head of development Kenichi Yamamoto was responsible for the new engine, which had greatly improved reliability and fuel-consumption, at the cost of a higher regular oil-consumption.
Apart from the unique engine the main appeal of the RX-7 was the low price, with it starting 4.800 $ under its direct competitor, the Porsche 924.
Until 1985 Mazda managed to sell just over 471.000 cars of the first generation, with a minor face-lift in 1981 (“SA22C/FB2”).
The RX-7 lived for two more generations, before retiring the name with the “Spirit R”-edition of the famous RX-7 FD3S in 2002.
The Mazda Series JC Cosmo - The Rotary Unicorn
In 1990 Mazda presented the Series JC Cosmo (alternatively called the Eunos Cosmo), a large sports-coupé that featured a 1.962ccm triple-rotor rotary-engine producing 220kw and 403 newton meters with the help of two turbochargers.
It is the largest rotary-engine ever sold by Mazda.
In its native market the car was limited to 180kph, unlimited it could reach 255kph.
Maximum torque was already present at as little as 1800rpm, allowing for impressive acceleration in return for high fuel-consumption.
Between February of 1990 and September of 1995 8.875 cars were sold, although 60% of which were equipped with an optional smaller twin-rotor engine, making the “full” version quite rare.
The car was only sold in Japan, market chances in Europe were seen as too limited and the “Amati”-brand for the US-market never materialized.
Yet still a handful of cars have since found their way into the US and Europe, although specific numbers are unknown.
The Mazda 787B - A Rotary wins Le Mans
Okay, the 1990 Mazda 787B isn’t road-going as much as it is racetrack-going, but I believe that it still deserves a mention.
Two cars were built in 1990 (named the Mazda 787) to compete in the 24h-race at Le Mans.
The 830kg light car was driven by a purpose-built quad-rotor naturally aspirated rotary engine sending 515kw (a limited output, more would have been possible) through a Porsche-made 5-speed gearbox to the rear wheels.
The engine was highly efficient for a rotary engine, featuring three spark plugs per chamber and seals made of silicon nitride for better efficiency.
But when the car only finished in 20th place in 1990 Mazda returned to the workshop to make a few changes.
The resulting car, the famous 787B, was visually identical to the predecessor, still using a Porsche gearbox and a UK-made carbon fibre monocoque.
The main difference was a new variable intake-design, allowing to adapt to different conditions.
Three updated cars were made, with the two original cars being updated as well.
The effort paid off, with the Number 55 car winning the race, sending three Jaguars to the places 2-4.
It was the first and so far only Japanese car to win the famous race, as well as the only car to ever win without using a piston-engine.
The Moller Skycar M400 - A Rotary Car-Plane-Helicopter-Something
Next up is the oddest entry on the list, and the one that stretches the definition of “road going” the most.
The Moller Skycar M400 appeared in the 1990s, being meant to be a private aircraft you can drive from your garage to the runway.
Or, alternatively, just drive to your destination.
Development started back in the 1970s, with the design changing from a flying saucer to what you see above.
Paul Moller, the designer of the machine, has said to have invested over 100 Million Dollars into the project.
The Skycar is meant to fly autonomously as soon as the driver/pilot dials in a destination, but so far neither the automated system worked nor did the Skycar ever take untethered flight at all.
On the 18th of October 2009 Moller filed for personal protection under the Chapter 11 of the federal bankruptcy law.
The main power-source are four propulsion fans mounted on variable mounts, allowing them to face forwards for horizontal propulsion or upwards for hovering/vertical take-off and landing.
Each of the four nacelles holds the rotor as well as two independent rotary engines made by a company called Freedom Motors, founded by an affiliate of Moller.
The purpose of eight engines is to still have at least four if any propeller’s engine fails.
The 530ccm engines are said to achieve 76kw when running on ethanol, while being able to run on any fuel, including both diesel and gasoline.
After filing for bankruptcy Moller has attempted to sell the prototypes on eBay, with both machines failing to sell.
They’re assumed to sit in storage, while Moller’s company has returned to the flying saucer design.
The latest status was an announced test flight in 2016, which has not taken place.
The Mazda RX-8 - Mazda's Farewell to the Rotary
Taking this post back to cars is Mazda’s RX-8, presented in 2003.
While the car was sold as the successor to the RX-7, it shares no parts with the predecessor.
The 2+2 coupé was available with either 141 or 170kw, the two versions differentiating in the design of the intake, the rev-limiter and a different ECU, with the more powerful version also getting a six-speed manual rather than the standard five-speed.
The engine was loosely based off the RX-7’s engine, but with a number of changes to reduce fuel-consumption by 20-30%.
Unfortunately, an RX-8 still needs about 30% more oil than comparable piston-engined powered cars.
The engine has a displacement of 1.302ccm, and revs as high as 9.000rpm in the more powerful version.
Mazda was very proud of being the last company to have a rotary-powered car on sale, which is reflected in the “Renisis”-symbol (a stylized rotor) being implemented into the car ten times, including the engine cover, the rear fog-light and the headrests.
In between 2005 and 2009 Mazda also sold a version of the RX-8 that could run on fuel or hydrogen, although it was probably more of a prestige-project than a car meant to earn money.
Mazda ceased production of the RX-8, and with that of rotary-engines, in 2012.
The basic platform lived on until 2015 in the Mazda MX-5 NC, which was used by a German dealership who sold a few dozen NCs with the RX-8’s drivetrain dropped in.
Mazda announced an RX-9 in late 2015, but no concrete information has been published since.
The Mazda Furai - A short-lived Beauty
The Mazda Furai (Japanese for “Sound of the Wind”) is a concept car presented by Mazda in January of 2008 as the last of their five “Nagare” concept cars that they had presented since 2006.
The 4.563mm long car weighted just 675kg thanks to a carbon-fiber chassis based off the C65 Le Mans race-car.
The car was powered by a triple-rotor rotary engine that produced 336kw from a combined displacement of two liters, made to run on bio-ethanol and said to be powerful enough to let the car reach 325kph.
The car carried the number 55 from the Le Mans-winning 787B, and Mazda considered participating in a Le Mans race with it.
After its appearance at the North American International Auto Show the car toured through a few magazines, before suddenly disappearing.
Only on the 29th of November 2013 did the public learn of the sad reason for the beloved car’s sudden disappearance.
The car had been shipped to Bentwaters Parks near London, England on the 19th of August 2008 in order to appear in an article in the Top Gear Magazine.
Mark Ticehurst, a professional race car driver, drove the car during a photography session when, at 11:52am, the engine bay caught fire while the car was moving at high speed.
Ticehurst was able to bring the car to a stop and bail out before the fire reached the cockpit, but due to the unfortunate location the fire-crews were initially unaware of the accident and took several minutes to reach the car.
By that point the car was engulfed in flames, with no hope to get away with repairable damage.
The fire was taken out within 8 minutes, and Mazda loaded up the charred remains and shipped them to their Advanced Design Studio in Irvine.
It is unknown where they went from there, it is assumed that they were simply disposed of.
The Audi A1 e-tron - A Return of the Rotary?
Ever since the end of the NSU Ro 80 in the 1970’s the rights to the Wankel engine were owned by Volkswagen, who put them to use in 2011 through Audi.
They presented the Audi A1 e-tron, an electric version of the A1 driven by a 75kw electric motor in the front.
Batteries placed in front of the rear axle can be charged through a cable, or via a small single-rotor 15kw Wankel engine that is located in the space usually occupied by a spare wheel.
The Wankel is actually a good choice for a range-extender, due to its small size, light weight and low noise.
The car was supposed to be sold starting in 2015, but was then delayed with no new release-date having been set yet.
All 30 cars made still exist, and are used by Audi at events for innovative cars or as a VIP-Shuttle on occasions like the German Television Award.
The list is by no means conclusive, especially in Japan a lot of cars were optionally fitted with small rotary engines due to them advantageous regarding the taxes.
All given data was researched to the best of my knowledge, if you find mistakes please let me know.