in Japan in 2002. The chief designer was . Another key designer was Wu-huang Chin (), a Taiwanese automotive artist who also worked on the Mazda MX-5 Miata. In Japan, sales were affected by this series' non-compliance with Japanese dimension regulations and Japanese buyers paid annual taxes for the car's non-compliant width. As the RX-7 was now considered an upper-level luxury sports car due to the increased width dimensions, Mazda also offered two smaller offerings, the Eunos Roadster, and the Eunos Presso hatchback. The sequential twin turbocharging system, introduced in 1992, was extremely complex and was developed with the aid of Hitachi. It was previously used on the exclusive-to-Japan Cosmo JC Series. The system used two turbochargers, one to provide of boost from 1,800 rpm. The second turbocharger activated in the upper half of the rpm range, during full throttle acceleration — at 4,000 rpm to maintain until redline. The changeover process occurred at 4,500 rpm, with a momentary dip in pressure to , and provided semi-linear acceleration from a wide torque curve throughout the entire rev range under normal operation. Under high speed driving conditions, the changeover process produced a significant increase in power output and forced technical drivers to adjust their driving style to anticipate and mitigate any over-steer during cornering. The standard turbo control system used 4 control solenoids, 4 actuators, both a vacuum and pressure chamber, and several feet of preformed vacuum/pressure hoses, all of which were prone to failure in part due to complexity and the inherent high temperatures of the rotary engine. A special high-performance version of the RX-7 was introduced in Australia in 1995, named the RX-7 SP. This model was developed to achieve homologation for racing in the Australian GT Production Car Series and the Eastern Creek 12 Hour production car race. An initial run of 25 cars were made, and later an extra 10 were built by Mazda due to demand. The RX-7 SP was rated at and of torque, a substantial increase over the standard model. Other changes included a race-developed carbon fibre nose cone and rear spoiler, a carbon fibre fuel tank (as opposed to the tank in the standard car), a 4.3:1 final drive ratio, 17-inch wheels, larger brake rotors and calipers. A "three times more efficient" intercooler, a new exhaust, and a modified ECU were also included. Weight was reduced significantly with the aid of further carbon