Mazda Eunos Cosmo 20B: The Three-Rotor Wankel

The Mazda Eunos Cosmo (1990-1995) is one of the rarest and most technologically unique Japanese production cars ever built. It's the only production car that used a three-rotor Wankel engine — the 20B-REW — and it was sold exclusively in Japan through Mazda's short-lived Eunos luxury brand. Only a few thousand were produced across the entire 1990-1995 production run, and the 20B-REW variant is even rarer, making it a holy grail for rotary enthusiasts.

The Three-Rotor Engine

The 20B-REW was a 2.0L (2,000cc equivalent displacement) three-rotor Wankel engine with sequential twin turbochargers. Specifications:

• Layout: Three-rotor Wankel, sequential twin turbo (two Hitachi HT-12 turbos)
• Displacement: 2.0L equivalent (true displacement: 1,962cc)
• Output: 280 PS (Japanese gentleman's agreement)
• Actual output: 320+ hp based on dyno testing
• Torque: 300+ lb-ft
• Fuel system: Sequential port injection, dedicated rotary cooling

The 20B-REW's three-rotor configuration made it unique in production car history. No other manufacturer had built a production three-rotor since NSU's failed NSU Ro 80 in the 1960s.

The Cosmo Platform

The Eunos Cosmo was built on a large, luxury grand tourer chassis. Body styles included:

• 2-door luxury coupe: The standard version
• Available engines: 13B-REW (2.0L twin-turbo, ~250 PS) or 20B-REW (2.0L twin-turbo triple-rotor, 280 PS)

The Cosmo's design was modern and sleek by 1990 standards — long hood, short rear deck, and executive coupe proportions. Its interior was plush and luxury-focused, with dedicated Cosmo-specific leather and wood trim.

Cosmic Technology

The Cosmo was full of 1990s Japanese luxury features:

• GPS navigation: One of the first production cars with built-in GPS (a rarity in 1990)
• Color CRT display: For vehicle information and navigation
• Voice recognition: Primitive by modern standards but advanced for the era
• CD player: When most cars still used cassettes

Production Numbers

Total Eunos Cosmo production: approximately 8,875 units between 1990 and 1995. Of those, only about 2,000 used the 20B-REW three-rotor engine (others used the 13B-REW twin-rotor). The 20B-REW variant is therefore the rarer collectible.

Today's Market

The Eunos Cosmo has become a cult collectible:

• Clean Cosmo 13B-REW: $25,000-$40,000
• Clean Cosmo 20B-REW: $50,000-$80,000
• Mint low-mileage 20B-REW: $100,000-$150,000+

Legacy

The Mazda Eunos Cosmo 20B is a monument to Mazda's rotary ambition. Three-rotor production cars don't exist anywhere else — not before, not after, not during. When Mazda killed the Eunos brand in 1996 and later shelved rotary production entirely (2012 with the RX-8), the Cosmo's three-rotor engine became the final chapter of production triple-rotor automotive engineering.

For rotary enthusiasts, the Cosmo 20B is one of the most important rotary cars ever built. It's the only production car you can own that uses a three-rotor Wankel — a technology that will probably never be produced again by any major manufacturer.