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Mazda has been pursuing the research of side exhaust porting for its rotary engine in an effort to improve the engine's fuel efficiency and exhaust emissions characteristics. The side exhaust porting configuration provides greater flexibility in setting port timing and shape, as compared to the peripheral exhaust porting configuration, which is in use in the current-generation rotary engines; the side exhaust porting configuration enables the selection of a port timing more favorable to reduced fuel consumption and exhaust emissions. The side exhaust port rotary engine used in this research has its exhaust port closure timing around the top dead center (TDC) and has no intake-exhaust timing overlap. As a result, burnt gasses entering the next cycle of combustion are reduced, thus enhancing combustion stability; also, the air-fuel ratio can be set leaner for improved fuel consumption.

Many sports cars have recently appeared on the market, and people's interest in and requirements for the cars are continuing to grow. The RX-7 was developed to be a first-class sports car that Mazda can be proud of worldwide as a trend leader for sports cars in the '90s. Among many innovations, its engine is the fruit of all the efforts Mazda has done to realize a “pure RE sports car” that takes every advantage of the rotary engine. This paper describes the aim of the development, main specifications, performance characteristics and major new technologies of the engine.

In today's automobile markets, there has been a strong and growing demand for higher output and better fuel economy engines. In order to improve rotary engines to satisfy this market demand, Mazda has devoted much effort to turbocharging system development and achieved the Sequential Twin Turbo System, which overcame the problems typical of conventional turbocharging systems; insufficient torque at low engine speeds and turbo lag. This system, which has two turbocharging units that operate in accordance with engine speeds (one unit at low engine speeds and both units at high engine speeds), features; (1) Compact and reliable turbo operation control system (2) Reduced temporary torque drop occurring when the second turbo starts With this new turbo system, Mazda's rotary engines have achieved an output performance equivalent to large displacement engines and smooth driving performance, while maintaining their light weight, compact size and better fuel economy.

Recent market trends show growing demands for automobile engines to attain better fuel economy and higher output while meeting the emission standards. To cope with these demands, Toyo Kogyo has made numerous improvements year by year on the rotary engine (1)*. A new engine that guarantees well-balanced fuel economy and vehicle performance has been developed. This engine uses a new induction system which incorporates the following technologies: 1) A variable intake port mechanism called the 6-Port Induction system (2). 2) A newly-developed intake passage which improves volumetric efficiency, utilizing the induction pressure variation generated in the intake manifold. This new induction system is simple in design, lightweight, and low in cost. It allows considerable improvement in performance over the entire engine speed range, without trading away fuel economy in normal vehicle operation.