The RENESIS rotary engine installed on the Mazda RX-8 symbolizes Mazda’s technological core. The history of rotary engine development and the growth of Mazda are intertwined and inseparable. Today, Mazda is the only company in the world that produces and sells rotary engine models. In 1961, Mazda engineers were deeply attracted by the potential advantages of rotary engines and decided to actively pursue the continuous development of rotary engines. Six years later and countless hours of hard work, in 1967, engineers proudly installed the world's first twin-rotor engine on the Cosmo Sports. Of course, the ongoing effort to perfect this unique engine never stops. To date, Mazda has produced nearly two million rotary engine-powered vehicles. The 24 Hours of Le Mans in Paris is a car competition that tests the limits of vehicle performance and endurance. In 1991, the Mazda 787B, powered by a rotary engine, became the first Japanese car to win this event. This unprecedented victory marked a glorious chapter in Mazda's automotive history. More importantly, this victory proves the company's mature technology in rotary engines. Rotary engines are often described as "stylish", "creative" and "dynamic". These three words can also be used to define Mazda's brand image and its unique technology. A Forty-Year Pursuit Ever since Mazda began researching and developing the perfect rotary engine, the company has successfully exploited the inherent lightweight, compact structure and high power performance of this engine while gradually overcoming its relatively low fuel consumption and exhaust emission levels. High disadvantages. On the 13BREW turbocharged rotary engine developed for the Mazda RX-7, Mazda has reached a technical peak in terms of maximum power in the development of rotary engines. But the passion and dreams that drive Mazda's rotary engine development never end. Engineers began working to make the powerplant more compact and improve its intake and combustion efficiency. These efforts were fully reflected in the MSP-RE, and this engine was installed on the RX-01 concept car launched at the 1995 Tokyo Motor Show. The naturally aspirated MSP-RE was subsequently mass-produced as the power system of the Mazda RX-8 and renamed RENESIS, which stands for "The RE (rotary engine)'s GENESIS" (meaning "The Genesis of the Rotary Engine"). RENESIS rotary engine. This naturally aspirated rotary engine is capable of producing a maximum power of 184 kW (250 PS) at 8,500 rpm (for Japanese high-power models). The compact and lightweight body makes the Mazda RX-8 It is able to adopt an advanced front-mid powertrain layout. Compared with the previous RX-7S, the engine position is lower and further back. Due to RENESIS' smooth performance, compact size and unique driving characteristics, the all-new Mazda RX-8 was named the International Engine of the Year in June 2003, shortly after its launch. As the only rotary engine manufacturer and a sports car manufacturer highly regarded by drivers around the world, Mazda continues to work hard to turn the company's dreams into reality. It is this dream and the passion we invest in the development of sports cars that makes Mazda customers have high expectations for the innovative RENESIS engine. A new generation of rotary engines The structure and working principle of the Wankel-type rotary engine Over the past 400 years, many inventors and engineers have wanted to develop a continuously operating internal combustion engine. It is hoped that one day the reciprocating piston internal combustion engine will be replaced by an elegant prime mover engine, whose trajectory should be very close to one of mankind's great inventions: the wheel.

In fact, the term "continuously operating internal combustion engine" first appeared in publications at the end of the 16th century. James Watt (1736-1819), the inventor of the connecting rod and crank mechanism, also studied rotary internal combustion engines. Especially in the past 150 years, inventors have made many proposals for the structure of rotary engines. In 1846, the geometry of today's rotary engine studio was sketched and the first concept engine using an externally rotating wheel line was designed. However, none of these concepts became practical until Dr. Felix Wankel developed the Wankel rotary engine in 1957. Dr. Wankel found the optimal shape of the trochoidal casing by studying and analyzing the feasibility of various rotary engine types. He has a deep understanding of the rotary valves used in aircraft engines and the airtight sealing mechanisms of superchargers. The use of these mechanisms in his design made the Wankel rotary engine practical. Modern rotary engines consist of a cocoon-shaped casing in which a triangular rotor is housed. The space between the rotor and the housing wall serves as an internal combustion chamber, and the pressure of the gas expansion drives the rotor to rotate. Like an ordinary internal combustion engine, a rotary engine must complete the four working processes of intake, compression, combustion and exhaust in its working chamber. If a triangular rotor is placed in the center of a circular casing, the working chamber will not change in volume as the rotor rotates inside the casing. Even if the mixture of air and fuel is ignited there, the expansion pressure of the combustion gas only acts on the middle of the rotor and does not cause rotation. This is why the inner circumference of the housing is designed as a trochoidal shape and is assembled with the rotor mounted on the eccentric shaft. Therefore, the volume of the working chamber changes twice per revolution, thereby realizing the four working processes of the internal combustion engine. On a Wankel-type rotary engine, the apex of the rotor moves with an elliptical casing around the inner circumference of the engine casing while maintaining contact with the output shaft gear on an eccentric orbit around the center of the engine casing. The orbit of the triangular rotor is defined using a phase gear mechanism. The phase gear includes an internal ring gear mounted on the inside of the rotor and an external gear mounted on the eccentric shaft. If the rotor gear has 30 teeth on its inside, the shaft gear will have 20 teeth on its outer circumference, giving a gear ratio of 3:2. Due to this gear ratio, the speed ratio between rotor and shaft is limited to 1:3. Compared with the eccentric shaft, the rotor has a longer rotation period. The rotor rotates once and the eccentric shaft rotates three times. When the engine speed is 3000 rpm, the rotor speed is only 1000 rpm. Comparison with traditional reciprocating engines Both reciprocating engines and rotary engines rely on the expansion pressure generated by the combustion of the air-fuel mixture to obtain rotational power. The mechanical difference between the two engines is the way in which expansion pressure is used. In a reciprocating engine, the expansion pressure generated on the top surface of the piston pushes the piston downward, and mechanical force is transmitted to the connecting rod, driving the crankshaft to rotate. In a rotary engine, expansion pressure acts on the sides of the rotor. This pushes one of the three faces of the triangular rotor toward the center of the eccentric shaft. (See PG in the picture). This movement is caused by two separate forces. One is the centripetal force pointing to the center of the output shaft (see Pb in the figure), and the other is the tangential force (Ft) that causes the output shaft to rotate. The interior space of the housing (or trochoidal chamber) is always divided into three working chambers. During the movement of the rotor, the volumes of these three working rooms are constantly changing, and the four processes of air intake, compression, combustion and exhaust are completed in the cycloidal cylinder. Each process takes place at a different location in the cycloidal cylinder, which is clearly different from a reciprocating engine. The four processes of a reciprocating engine are all carried out in one cylinder. A new generation of rotary engines The exhaust volume of rotary engines is usually expressed in terms of unit working chamber volume and the number of rotors. For example, for a twin-rotor engine model 13B, the displacement is "654cc × 2". The unit working chamber volume refers to the difference between the maximum and minimum volumes of the working chamber; while the compression ratio is the ratio of the maximum and minimum volumes. The same definition is used on reciprocating engines.

Changes in operating volume of a rotary engine, as shown in the figure on the previous page, and comparison with a four-cycle reciprocating engine. Although the chamber volume changes steadily in a wave-like pattern in both engines, there are clear differences. The first is the rotation angle of each process: a reciprocating engine rotates 180 degrees, while a rotary engine rotates 270 degrees, which is 1.5 times that of a reciprocating engine. In other words, in a reciprocating engine, the crankshaft (output shaft) makes two revolutions (720 degrees) in four working cycles; while in a rotary engine, the eccentric shaft makes three revolutions (1080 degrees) and the rotor makes one revolution. In this way, the rotary engine can achieve longer process times and produce smaller torque fluctuations, resulting in smooth and smooth operation. In addition, even at high speeds, the rotor rotates quite slowly, allowing for looser intake and exhaust times, which facilitates the operation of systems that can obtain higher power performance. Characteristics of the Wankel rotary engine ● Small size and light weight The rotary engine has several advantages, the most important of which is reduced size and weight. In terms of quietness and smoothness of operation, the twin-rotor RE is equivalent to an inline six-cylinder reciprocating engine. Under the premise of ensuring the same output power level, the design weight of the rotary engine is two-thirds that of the reciprocating engine. This advantage is extremely attractive to automotive engineers. Especially in recent years, requirements in terms of crashworthiness (crash safety), aerodynamics, weight distribution and space utilization have become increasingly stringent. ● Simplified structure Since the rotary engine directly converts the expansion pressure generated by the combustion of the air-fuel mixture into the rotational force of the triangular rotor and eccentric shaft, there is no need to set up connecting rods. The air inlet and exhaust port rely on the movement of the rotor itself to open and Closed; there is no need for a valve train, including timing belts, camshafts, rocker arms, valves, valve springs, etc., which are an essential part of a reciprocating engine. In summary, the components required to form a rotary engine are significantly reduced. ● Uniform torque characteristics According to the research results, the rotary engine has a fairly uniform torque curve across the entire speed range. Even in the two-rotor design, the torque fluctuations during operation are at the same level as the in-line six-cylinder reciprocating engine. The three-rotor arrangement is smaller than that of the V-type eight-cylinder reciprocating engine. ● Quieter operation and less noise For reciprocating engines, the piston movement itself is a source of vibration, and the valve train also produces annoying mechanical noise. The smooth rotational motion of a rotary engine produces very little vibration, and its lack of a valve train results in smoother and quieter operation. ● Reliability and durability As mentioned before, the rotation speed of the rotor is one-third of the engine speed. Therefore, when a rotary engine is running at 9000 rpm, the rotor is rotating at about one-third of that speed. In addition, because the rotary engine does not have those high-speed moving parts, such as rocker arms and connecting rods, it is more reliable and durable in high-load movements. The victory at Le Mans in 1991 fully proved this point.