Last year, Mazda celebrated forty years of rotary-engine zoom. We ate cake, fantasized that a new rotary might soon resuscitate the RX-7, and then began compiling these cool facts related to Felix Wankel’s wonder motor.
Herr Wankel (1902-88) endured major hardship. His father was a World War I casualty. Poverty denied him an apprenticeship and a university education. During his twenties, he was a member of the Hitler Youth. The Nazis imprisoned Wankel in the 1930s, and the French locked him up again in 1945.
Throughout his life, Wankel never held a driver’s license. Munich’s technical university presented him with an honorary doctorate degree in 1969.
At seventeen, Wankel dreamed that he drove a car he had constructed to a concert. To friends in the dream, he bragged, “My car has a new type of engine, half turbine, half reciprocating. It’s my invention!”
Five years later, Wankel opened a shop in Heidelberg to commence work on his dream machine. His first patent was issued in 1929. Before and during WWII, Wankel worked on rotary valves and seals for aircraft engine makers, including BMW and Daimler-Benz.
Wankel’s experimental engine ran in 1957, producing 21 hp. Both the rotor and its housing rotated in this early design.
Wankel’s rotary engine is the only internal-combustion engine invented in the twentieth century to achieve production status.
Mazda president Tsuneji Matsuda signed a study contract with Wankel’s development partner, NSU, in 1961. Mazda’s first experimental rotary engine fired up later that year.
Kenichi Yamamoto became chief of Mazda’s rotary research department in 1963. After problems with apex seals were solved, experimental engines were capable of running 300 hours at high speed.
More than a dozen automotive, motorcycle, marine, and industrial manufacturers signed license agreements to develop rotary engines. Alfa Romeo, AMC, Citroën, Ford, GM, Mercedes-Benz, Nissan, Porsche, Rolls-Royce, Suzuki, and Toyota all joined the rotary club.
Mazda and NSU raced to produce the first rotary-powered automobile. NSU won with its $2979, 64-hp, single-rotor Spider two-seater introduced in 1964. Mazda countered with a display of two- and four-rotor engines at that year’s Tokyo Motor Show.
Following the Cosmo Sport 110S’s introduction at the 1966 Tokyo show, Mazda began selling its first rotary car the following year. Only 1176 two-rotor coupes were produced through 1972.
After NSU’s two-rotor Ro80 luxury sedan bowed in 1967, owners traditionally saluted one another on the road with fingers raised showing how many times the apex seals in their engines had been replaced. NSU merged with Audi in 1969, and the Ro80’s Wankel was shelved in ’77.
The rotary engine’s competition baptism came in 1968, when a Cosmo Sport finished fourth overall in the eighty-four-hour Marathon de la Route endurance race at the Nürburgring.
Rotary engines were attractive to some makers striving for exhaust-emissions compliance, because they produced lower NOx pollution than piston engines. Poor thermal efficiency and sealing challenges ultimately thwarted the engine’s popularity.
Rotaries are simpler, lighter, and more compact than piston engines of comparable power. Unlike reciprocating engines, their moving parts are in perfect balance. Since no valve train components are present, friction is substantially lower.
While there are only three major moving components – two rotors, one eccentric shaft – in a Mazda rotary engine, nearly 100 seal-related parts are also required.
Each rotor forms three working chambers inside the figure-eight-shaped trochoid housing. Rotors turn one-third as fast as the eccentric shaft that takes power out of the engine. As a result, each chamber delivers torque over 270 of the 1080 degrees required to complete the combustion process, versus 180 out of 720 degrees for a piston engine. This long-duration torque delivery underlies the rotary’s smooth operation.
The first racing victory for a rotary engine on American soil occurred in 1973, when Patrick Bedard, an editor at Ann Arbor’s other car magazine, drove a Mazda RX-2 to a noisy win at a Lime Rock IMSA RS event.
In 1974, a Mazda RX-3 set a 160-mph Bonneville record. Three subsequent records, topped off by a 242-mph two-way average in 1995, were set by one normally aspirated and two turbocharged Mazda RX-7s.
The California rotary-engine-tuning emporium, Racing Beat, was founded in 1971 by engineer Jim Mederer and business manager Ryusuke Oku. Racing Beat constructed all the engines and three of the race cars cited in items 18 and 19. Mederer built the 930-hp, twin-turbo rotary for the RX-7 he drove to the C-Blown Modified Sports land-speed record at Bonneville in 1995.
Other Racing Beat accomplishments include the NHRA Modified Eliminator championship in 1978 and the IMSA GTU title in 1980. Racing Beat rotaries have powered midget racers, NASA research planes, private aircraft, IMSA GTP cars, Jim Russell single-seaters, off-road trucks, seismic drilling rigs, and several drag racers.
Hercules, Norton, Suzuki, and Van Veen sold rotary-powered motorcycles during the 1970s and ’80s. A shrieking Norton won the British F1 series in 1989.
The miniature OS-Graupner rotary engine for model planes weighs less than a pound, revs to 18,000 rpm, and produces 1.3 hp. Manufactured in Japan, it has been sold since 1970 with few design changes.
Mazda‘s RX-7 is the most successful car in IMSA history, with more class wins than any other model. RX-7s scored twelve Daytona 24-Hour GTU victories in a row beginning in 1982, ten successive GTU championships, and their 100th victory in 1990. Rotaries currently power RX-8s in the Grand-Am GT series and formula racers in the Star Mazda series.
Mazda RX-7s earned finishes at the 24 Hours of Le Mans in 1980 and 1982. Group C victories followed in 1983 and 1984.
MazdaSpeed (originally Mazda Auto Tokyo’s motorsports department and later the factory’s racing team) began campaigning for an overall Le Mans victory in 1988, with a mighty four-rotor engine in a car designed and developed in-house. On the fourth attempt, in 1991, a 700-hp 787B driven by Bertrand Gachot, Johnny Herbert, and Volker Weidler took the checkered flag. Teammates finished sixth and eighth overall.
Mazda built and sold three generations of rotary-powered RX-7s for twenty-five years beginning in 1978. There is hope that a new fourth-generation sports car might appear in 2011.
At the current RX-8 sales rate, Mazda will build its two-millionth rotary engine next year.
Characteristics that hamper the rotary’s fuel efficiency enhance its suitability for hydrogen fuel. Mazda began studying hydrogen-combustion rotaries in 1991. In 2006, a few RX-8s capable of running on either gasoline or hydrogen were offered for lease in Japan.
Mazda’s Premacy (known as the Mazda 5 in the United States) hydrogen-fueled, rotary-powered hybrid concept vehicle presented at last year’s Tokyo Motor Show seats five, accelerates to 62 mph in eleven seconds, and has a 125-mile range. It uses a rotary engine to power a generator that supplies current to both an AC drive motor and a lithium-ion battery pack.
Racing Beat’s newest rotary (shown below with Ryusuke Oku and Jim Mederer) produces more than 300 hp, revs over 10,000 rpm, and weighs only 180 pounds. Intake and exhaust ports are both peripheral. A Motec engine-management system controls fuel injection and ignition. Regrettably, this racing rotary is not viable for road use.
Kenichi Yamamoto, whose sister was an A-bomb victim, joined Toyo Kogyo, the firm that became Mazda, in 1946. Initially skeptical of the rotary engine, he realized its development was crucial to his firm’s independence in the face of efforts to consolidate the Japanese auto industry. Yamamoto, who implored his engineers to think rotary thoughts day and night, kept paper and pencil at his bedside.
By 1973, over half of Mazda’s production was rotary-powered. The first oil crisis and the resulting frenzy over fuel efficiency drove Mazda into debt. Yamamoto, deemed a “war criminal” by management for espousing rotaries, kept the faith. As managing director, he spurred work on the RX-7 and new piston-powered small cars to restore Mazda’s vitality.
Yamamoto became Mazda’s president in 1984 and chairman in 1987. Two notable nonrotary moves during his watch included building an assembly plant in Flat Rock, Michigan, and introducing the Miata. Upon retirement in 1992, Yamamoto commenced an advisory role with Mazda.
Takaharu Kobayakawa studied mechanical engineering before joining Mazda in 1963 to work on rotary engines. Following eight years of development assignments under Yamamoto, he was dispatched to the United States in 1971 to monitor the rotary’s vitality here.
Called back to Japan, Kobayakawa worked in public relations before assisting with the engineering of the second-generation RX-7. While managing development of the twin-turbocharged third-generation RX-7 launched in 1991, he also guided Mazda’s Le Mans effort. Rounding out his thirty-seven-year career, Kobayakawa later headed corporate communications, global design, and U.S. R&D efforts. Inexplicably, he became an automotive journalist upon retirement from Mazda.
Work on a new rotary engine began in earnest last year. What Mazda calls the Renesis 16X is 23 percent larger in displacement and 20 percent lighter, thanks to a switch from iron to aluminum for the three side housings. More eccentricity (the rotary’s version of stroke) is aimed at shifting peak torque lower in the rev range. Direct fuel injection and additional displacement should boost output to 275 hp or more.
Mazda engineer Seiji Tashima, who was instrumental in developing the side exhaust ports for the RX-8’s Renesis 13B engine, now heads 16X development.
Miniature Wankels have been used to operate seatbelt pretensioner devices in Mercedes-Benz and Volkswagen cars. When sensors determine that a crash is imminent, an electrical signal triggers the release of pressurized gas into a sealed chamber, causing the take-up reel to spin. Each unit provides up to three cycles of rotation.
Your author and Automobile Magazine’s resident rotor head played a role in items 18 and 19. The 238-mph record Don Sherman set at Bonneville driving a 530-hp RX-7 turbo in 1986 still stands. The first-generation RX-7 he treasures has logged a mere 21,764 miles over thirty years of ownership.