The third generation of the RX-7, FD (with FD3S for Japan and JM1FD for the USA VIN), featured an updated body design. The 13B-REW was the first-ever mass-produced sequential twin-turbocharger system to export from Japan, boosting power to 255 PS (188 kW; 252 hp) in 1993 and finally 280 PS (206 kW; 276 hp) by the time production ended in Japan in 2002.
In Japan, sales were affected by the fact that this series RX-7 no longer complied with Japanese Government dimension regulations, and Japanese buyers were liable for yearly taxes for driving a wider car compared to previous generations. As the RX-7 was now considered an upper-level luxury sportscar due to the increased width dimensions, Mazda offered two smaller sports cars, the Eunos Roadster, and the Eunos Presso hatchback.
The sequential twin turbocharged system, introduced on this series in 1992, was a very complex piece of engineering, developed with the aid of Hitachi and previously used on the exclusive to Japan Cosmo series (JC Cosmo=90–95). The system was composed of two turbochargers, one to provide boost at low RPM. The second unit was on standby until the upper half of the rpm range during full throttle acceleration. The first turbocharger provided 10 psi (0.7 bar) of boost from 1800 rpm, and the second turbocharger was activated at 4000 rpm to maintain 10 psi (0.7 bar) until redline. The changeover process occurred at 4500 rpm, with a momentary dip in pressure to 8 psi (0.6 bar), and provided semi-linear acceleration and a wide torque curve the throughout the entire rev range under “normal operation”. However, under performance driving the changeover process produced a significant increase in power and forced technical drivers to adjust their driving style to anticipate and mitigate any over-steer during cornering. Many owners modified their turbo control systems into a parallel system by removing the exhaust manifold Turbo Control Valve and the turbo coupling “y-pipe” Charge Control Actuator and valve in order to remove the changeover process and to simplify the control system for reliability. Turbo lag was greatly increased below 4500 rpm, but smooth and linear boost could be obtained. The stock 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 to complexity and the inherent high temperatures of the rotary engine.Discover more on Wikipedia