In the early 1960s,
during the initial development stage of the rotary engine, Mazda
designed and investigated three types of rotary engine: those with
two rotors, three rotors, and four rotors. The single-rotor version,
prototypes of which were completed by NSU, could run smoothly at
high speeds, but in the low speed range it tended to be unstable,
with high levels of vibration and a lack of torque. This is due to
the fact that a single rotor engine has only one combustion phase
per revolution of
the output shaft, resulting in a large torque conversion, which is a basic characteristic of this engine format.
the output shaft, resulting in a large torque conversion, which is a basic characteristic of this engine format.
Mazda then decided to
develop a two-rotor engine, in which the torque fluctuations were
expected to be at the same level as a 6-cylinder 4-stroke
reciprocating engine.
The first two-rotor test
engine, the type L8A (399cc single chamber volume), was an original
Mazda design and was mounted in a prototype sports car (type L402A,
an early prototype of the Cosmo Sport) designed specifically for the
rotary engine.
In December 1964,
another two-rotor test engine, type 3820 (491cc single chamber
volume) was designed. It soon evolved into the mass-production
trial-type L10A. The 60 Cosmo Sport prototype cars in which
this engine was installed were driven for over 600,000 kilometers in
Japan, during which Mazda collected critical data that was used in
the preparation of the series production model. Once in production,
the L10A designation given to the prototype became the type
designation of the 1968 Cosmo Sport.
Moreover, in recognition
of the large potential of the rotary engine, Mazda invested heavily
in imported and exclusive machine tools, and proceeded with the
trial manufacturing of multi-rotor rotary engines, including three
and four-rotor versions. Those prototypes were installed on a
prototype mid-engine sports car, the Mazda R16A. Test drives were
carried out on a high speed test circuit at Miyoshi Proving Ground,
completed in 1965. The course was the most advanced in Asia at that
time.
World�s First Two-Rotor Rotary
Engine
On May 30th, 1967, Mazda
began selling the world�s first two-rotor rotary engine car, the
Cosmo Sport.
It featured a
110-horsepower type 10A engine (491cc single chamber volume)
equipped with newly
developed apex seals made with pyro-graphite, a highstrength carbon material, and specially processed aluminum sintering. This apex seal was the result of Mazda�s independent development work and proved durable through 1,000 hours of continuous testing. Even after a 100,000 km test drive, it showed only slight wear of just 0.8 mm and an absence of chatter marks.
developed apex seals made with pyro-graphite, a highstrength carbon material, and specially processed aluminum sintering. This apex seal was the result of Mazda�s independent development work and proved durable through 1,000 hours of continuous testing. Even after a 100,000 km test drive, it showed only slight wear of just 0.8 mm and an absence of chatter marks.
The intake system
featured a side-port configuration coupled with a two-stage
four-barrel carburetor, to keep combustion stable at all speeds. For
the ignition system, each rotor was equipped with two spark plugs so
that stable combustion could be maintained in cold and hot weather
conditions alike, as well as on urban streets and expressways.
The Cosmo Sport was
road-tested over a 6-year period and more than 3 million kilometers.
The year
after it went on sale, Mazda entered Cosmo Sport in the gruelling endurance race, �Marathon de la Route� of 1968. The car finished fourth in the race against formidable competition from Europe, and its futuristic styling and superb driving performance delighted car buffs throughout the world.
after it went on sale, Mazda entered Cosmo Sport in the gruelling endurance race, �Marathon de la Route� of 1968. The car finished fourth in the race against formidable competition from Europe, and its futuristic styling and superb driving performance delighted car buffs throughout the world.
