Genesis for the Rotary.
The Rotary engine was doomed to never fulfill its immense potential. This is the story of one of the automotive worlds biggest 'what ifs?'
1951. Neckarsulm. Germany. Felix Wankel is developing his concept for a new engine. Instead of pistons, reciprocating in cylinders, his new engine will use an almost triangular rotor, rotating in an epitrochoid (oval) housing. Where a traditional engine has pistons continuously and rapidly changing direction, the rotary engine, as it would become known, had its rotor(s) rotating in one constant direction.
Felix Wankel. Godfather of the Rotary. (Image Credit to Wikimedia Commons.
So, in theory the 'Wankel Engine' would revolutionise the motoring industry. A rotary could have a far greater specific output - power per litre; a much better power-to-weight ratio; a higher redline and much smoother power delivery when compared to traditional combustion engines. Furthermore the rotary design was modular, rotors could be stacked in their combustion chambers almost infinitely in theory - single, twin, triple or quad rotor setups were all possible. And some maintain more is possible, though it has never been deemed viable.
Back to the story; it was 1957 before Wankel's first prototype would run, dubbed internally as the DKM engine. It produced 21 HP (16 kW), not masses, but the Wankel engine was now cemented as a real possibility. NSU engineer Hans Dieter Paschke created a second prototype the same year, with the goal of simplifying the concept. Where Wankel's engine would require a full teardown for something as routine as a spark-plug change, Paschke's KKM engine was far simpler and easier to maintain. The simplicity robbed the engine of performance and character, however. With Wankel later remarking to Paschke "you have turned my racehorse into a plough-mare."
Wankel's DKM Prototype. (Image Credit to Wikimedia Commons)
Wankel's design was chosen for further development, and over the next four years various iterations were made on Wankel's formula, and in 1961 the biggest and most famous name in the Rotary world would enter the fray.
Mazda signed a joint development contract with NSU. And the two rivals worked together with the goal of getting a Rotary engine car to the market. Despite developing the technology jointly, they were competing for the honour of bringing the new engine to open market. And despite Mazda's later dominance of the Rotary Market; they didn't win the rotary launch race, even if they would go on to win the Rotary War.
1964. The world is introduced to the concept of a Wankel engine, in the NSU Spider. Based on the NSU Sport Prinz Coupe, but with a retractable soft-top and a Rotary powerplant. The Spider was a small, lightweight sports car in the same vein as the MG Midget. The rear mounted 500CC Single Rotor produced 54HP (40kW). This wasn't huge but in a car that weighed only 750KG it was no slouch for the time. 0-60 was around 14 seconds - pedestrian by todays standards, but not hopeless back then. The Rotary was revvy too, allowing up to around 7,000 RPM - though prolonged high revs could prove catastrophic (The safe rev-limit was a few hundred revs lower).
The First ever Rotary Powered car. The NSU Spider. (Image Credit to Wikimedia Commons)
As revolutionary as the Spider was, it didn't last long. Selling in low volumes was always the intention, but after three years and 2,375 units the Spider was retired. And though not a runaway success; the Rotary concept worked. And the Wankel technology had definite potential in racing. As was proved by Al Auger in California. With a standard Spider, fitted with a mandatory roll cage and racing tyres, Auger entered into SCCA road races in California. Competing in a class populated by 850cc powered, purpose built racing machinery due to the organisers' lack of knowledge about the Rotary he finished second in the championship for both 1966 and '67 in his production NSU. No small feat.
With the retirement of the Spider, came the next advancement for Rotary technology. The Ro 80. For the first time a family car would be powered by a Twin-Rotor Wankel engine. The 1 Litre powerplant developed 115 HP (85 kW), a brilliant specific output and a more than respectable tally for the late sixties. The Ro 80 was met with a glowing reception. Loved by reviewers for its smoothness, handsome exterior, all round disc brakes and its semi-automatic transmission. The Ro 80 won Car of the Year in 1968. But despite early promise, all was not well.
NSU's second attempt at the Rotary Car. (Image Credit to Wikimedia Commons)
NSU's new car created the whole image of the unreliable Rotary., and while they undoubtedly are, the Ro 80's catastrophic unreliability may well have scared other manufacturers away from the technology. More manufacturers and development might just have made the Rotary viable, but alas that is neither here nor there.
Such was the Ro 80's unreliability that new engines would be needed every 24,000-32,000 miles. Poor understanding of the engine technology by dealers and technicians, combined with the Wankel derived design being so complex, meant the unreliability problem was exacerbated. The crux of the issue, as many of us now know was the apex seals. The seals on the vertices of the rotor would wear, and different parts of the seals would wear at different rates. This allowed the products of combustion to leak from the combustion chambers, eventually destroying the engine.
An allegory for the catastrophe of the Ro 80 was a practice owners took up in the 70s. When two Ro 80s crossed paths the owners would stretch their hands out of the window and signal how many of their egines had ended up on a scrapheap. The Ro 80 destroyed NSU through a mangled reputation and an avalanche of warranty claims. Two years after Ro 80 launched, VW bought NSU and merged them with Auto Union to form what we now know as Audi.
The Twin Rotor in the last NSU. (Image Credit to Flickr)
With NSU's demise Mazda became the Rotary's sole vendor. Mazda's Cosmo reached market in 1967, the same year as Ro 80. From there the Rotary went on to reasonable successes under the Japanese marque. The Cosmo stayed in production until 1996. Culminating with the JC Eunos Cosmo. Powered by a twin turbo Three-Rotor. The 20B-REW. 300HP (224 kW) was impressive and despite being too costly the last Cosmo was a great technical achievement for Mazda.
The Ultimate Iteration of Mazda's first Rotary. The 20B Eunos Cosmo. (Image Credit to Wikimedia Commons)
Mazda are also responsible for the most successful Rotary Powered car of all time. The RX-7. The Twin-Turbo, Twin-Rotor sports car lived a long life - 22 years over three generations. The FD Spirit R being the culmination of 50 years of Rotary development for the road. Sequentialy twin-turbocharged and with 280 HP the RX-7 was fast, free revving and well-mannered in the bends. The new millennium brought the RX-8. A four-door coupe with many of the same characterisitics as the RX-7. But with the RX-8's death in 2012 came the death of Rotary technology in general. Despite Mazda's persistence the reliability, high oil and fuel consumption and unacceptable emissions were never solved. No one else took Rotary power seriously and it seems now that the Rotary has passed the point of no return.
The Culmination of 50 Years of work. The FD RX-7 Spirit R.
Wankel's creation had so much potential, but was doomed to an ignominious early death. The quirky alternative power unit was never developed to its full potential and as such Rotary cars filled a niche market and missed out on major glory. Aside from one weekend in 1991. When the ear-splitting Four Rotor 787B won the 24 Hours of Le Mans. The summit of a story that would ultimately end in tragedy.
The Fastest Rotary. The ear-splitting 787B. (Image Credit to Wikimedia Commons)
Thank you for reading, I hope you enjoyed the article. If you did a like would be greatly appreciated, and feel free to comment opinions about the Rotary Engine.