Although it was well-received, the Mazda RX-Vision sports car concept that debuted at the 2015 Tokyo motor show hasn't been green-lit for production, Automotive News reports. A team of 50 Mazda engineers have worked tirelessly for the past eight years to find the breakthrough needed to overcome the inherent shortcomings of the rotary engine. That breakthrough, however, has proven elusive.

"We have a dream that one day, this design with a rotary engine will achieve a level that customers will accept," Mazda CEO Masamichi Kogai told reporters through an interpreter. "We have rotary engine fans and they will not be satisfied if we have the same exact rotary engine from before."

Despite their simplicity of design, rotary engines are typically less fuel efficient and less reliable than piston engines. They also tend to produce higher emissions. In order to avoid putting pressure on its engineers, Mazda hasn't set a target date for a rotary-powered sports car.

The RX-Vision concept uses a modified version of the 16X rotary engine developed last decade that was used in the Mazda Taiki concept shown in 2007. Although the engineering team has yet to find the breakthrough needed to meet the engine's performance targets for a production sports car, the automaker refuses to give up on development of the engine.

If that breakthrough happens, the automaker would use a modified and reinforced version of the Miata's front-engine rear-drive chassis for the rotary-powered sports car. Kogai called the Miata's chassis "close to perfection."

"These 50 engineers want to develop the rotary engine, therefore they joined Mazda," said Kiyoshi Fujiwara, head of Mazda's research and development. "If I stop the rotary engine, probably they want to leave." Fujiwara said the small team is fiercely dedicated to the project.