JDM Mazda 20B-REW 3-Rotor Twin-Turbo Engine – Eunos Cosmo JC Complete Longblock

The Mazda 20B-REW is a 2.0-liter, triple-rotor twin-turbocharged Wankel rotary engine, widely regarded as the most powerful and desirable rotary engine ever produced for a production vehicle. Produced exclusively for the Eunos Cosmo (JC series) from 1990 to 1995, this engine features three rotors (654cc x 3 = 1,962cc), a factory sequential twin-turbo system, and a level of smoothness and torque that no two-rotor can match . With only approximately 3,550-4,000 units ever produced, the 20B-REW is the holy grail of Mazda rotary engines .

The 20B-REW is fundamentally a 13B with an additional rotor added to the eccentric shaft. This required a split-shaft eccentric shaft design using taper joints secured with half-moon keys – the same technology proven in Mazda's Le Mans-winning 767 and 787B race cars

• Triple-Rotor Configuration: Three 654cc rotors provide 50% more displacement than the 13B-REW, delivering exceptional smoothness and a unique, deep exhaust note that no two-rotor can replicate .

• Factory Sequential Twin-Turbo System: The 20B-REW was among the first Japanese production engines to feature a sequential twin-turbo setup. A smaller primary turbo spools quickly for low-end response, while a larger secondary turbo seamlessly takes over at higher RPM for sustained top-end power .

• Massive Low-End Torque: With over 380 N·m (280 lb-ft) of torque available at just 1,800 RPM, the 20B-REW launches with authority unmatched by any two-rotor . Peak torque arrives at only 3,000 RPM.

• 9.0:1 Compression Ratio: Lower than the Renesis (10.0:1), the 20B's compression ratio is ideal for forced induction and high-boost applications.

• Six Spark Plugs (2 per rotor): Leading and trailing spark plugs per rotor chamber ensure complete combustion across the long rotary flame front.

• 2 Injectors per Rotor: Factory electronic fuel injection with dual injectors per rotor for precise fuel delivery under all conditions.

• Electronic Boost Control: Factory ECU-managed boost control for consistent power delivery.

• Cast Iron Side Housings with Aluminum Rotor Housings: Robust construction capable of supporting 500-800+ horsepower with proper modifications.

The 20B-REW was only available with a 4-speed electronically controlled automatic transmission from the factory (EC-AT) . The transmission features three modes:

• Normal: Standard automatic operation

• Power: Holds gears longer for performance driving

• Hold: Manumatic mode for manual gear selection

For manual transmission conversions, the 20B bolts directly to the RX-7 FD's 5-speed manual transmission (bellhousing pattern is shared) . However, a standalone aftermarket ECU (Haltech, Link, Adaptronic, Microtech, MoTeC, etc.) is required for manual conversion, as the factory Cosmo ECU is tuned exclusively for automatic operation .

• 1x Mazda 20B-REW Complete Longblock (3-rotor assembly with rotor housings, side housings, and irons)

• 1x Intake Manifold with throttle body

• 1x Complete Sequential Twin-Turbo System (Hitachi HT-12 primary and secondary turbos)

• 1x Cast Iron Exhaust Manifolds (twin entry)

• 1x 4-Speed Automatic Transmission (EC-AT with torque converter) – if specified

• 1x Engine Wiring Harness (Cosmo JC specific – if included)

• ECU, alternator, starter, ignition components, intercooler, and accessories.