Mazda 20B Engine for Sale | 20B-REW Triple-Rotor Sequential Twin-Turbocharged Rotary Engine | Direct Fit JDM Eunos Cosmo (1990 to 1995)

Mazda 20B Engine for Sale: The Ultimate Triple-Rotor Powerhouse

What happens when you push Mazda’s rotary engineering to its peak? You get the Mazda 20B engine. Equipped with a rare and unique triple-rotor design, this 20B engine for sale here is the epitome of Mazda’s automotive innovation. The motor surpasses piston engines of similar configuration when it comes to power-to-weight ratio, and the iconic roar of three rotors spinning to redline is bound to send a chill down your spine. Do not hold your project car back , check out the Mazda 20B engine for sale here and unleash one of the rarest production rotary engines ever made.

The Legendary Mazda 20B: A Triple-Rotor Marvel

The Mazda 20B engine is a unique piece of automotive engineering. Manufactured from 1990, this legendary engine originally powered the Eunos Cosmo , Mazda’s JDM-only flagship grand touring coupe. The 20B-REW shares its design philosophy with the legendary 13B-REW (used in the RX-7 FD) but adds a third rotor to the architecture, dramatically increasing displacement and power potential.

This engine has also proven its worth in motorsport and engine swap applications. The 20B is widely regarded as the “holy grail” for rotary enthusiasts and performance builders alike, particularly those building RX-7 FD or FC swap projects where the additional displacement and power of the 20B make a tremendous difference in real-world performance.

Important Specification Notes

We want to provide honest, transparent specifications for the 20B engine, which can vary by source:

The official factory rating of 280 PS reflects the Japanese gentleman‘s agreement that capped domestic-market production car ratings at 280 PS during the 1990s. Mazda was legally required to advertise 280 PS for the Japanese market, but actual measured output was approximately 300 HP. After-market dyno tests of healthy 20B engines typically read 280 to 305 HP depending on supporting modifications.

For practical buying purposes, expect a healthy 20B to produce 270-300 HP and 280-300 lb-ft of torque, with significant tuning potential beyond that.

Engine Overview: The Eunos Cosmo and the 20B-REW

The 20B-REW was developed for and used in only one production vehicle: the Eunos Cosmo.

The Eunos Cosmo (also called the Mazda Cosmo internationally) was:

• A flagship JDM-only luxury grand touring coupe produced 1990 to 1995

• Mazda’s premium offering during the JDM bubble economy era

• Approximately 8,875 total units produced over the 5-year run

• Featured the world’s first production GPS navigation system

• Available with the 20B-REW as the top-tier engine option (a 13B-REW twin-turbo was the lower option, similar to the RX-7 FD)

• Never officially sold in the United States , all 20B engines in North America were imported through specialty channels

The 20B vs Other Mazda Rotaries

To understand the 20B’s position in Mazda rotary history:

The 20B-REW remains the most powerful production rotary engine Mazda ever produced.

Why the 20B is the Holy Grail for Rotary Enthusiasts

Several factors make the 20B the most desired rotary engine for performance builders:

• Three Rotors Equals More Power: Three rotors produce 50% more displacement than the 13B, with corresponding power potential

• Sequential Twin-Turbo System: Same proven sequential twin-turbo architecture as the 13B-REW but flowing more air through the larger engine

• Three-Rotor Exhaust Note: The signature 20B exhaust note is even more distinctive than the 2-rotor RX-7 , a higher-pitched, more complex sound that has cult following

• Rarity: Only used in the JDM-only Eunos Cosmo, total production approximately 8,875 cars with 20B as the top engine option , far fewer 20B-equipped Eunos Cosmos exist

• Engine Swap Appeal: Fits in the RX-7 FD engine bay with custom fabrication , a popular high-performance upgrade from the stock 13B-REW

• Tuning Potential: With bigger turbochargers and supporting modifications, 20B engines can produce 500-800+ HP

Engine Swap Applications

The 20B is most commonly used for engine swaps into:

• Mazda RX-7 FD (1992-2002): The most popular 20B swap target. Requires custom engine mounts, modified subframe clearance, custom exhaust manifolds, often a different transmission, and significant supporting modifications. A successful 20B-into-FD build is one of the most coveted rotary builds.

• Mazda RX-7 FC (1986-1991): Less common than FD swaps but still done. Engine bay is similar but smaller; more extensive fabrication required.

• Mazda RX-3 and RX-4: Classic rotary platforms where 20B swaps create extraordinary performance cars.

• Custom Drift and Time Attack Cars: The 20B is popular in custom drift cars and competition vehicles where the power-to-weight ratio and exhaust note are advantages.

Features of the Mazda 20B Engine

• Triple-Rotor Configuration: Three rotors arranged inline, each rotor 654 cc nominal displacement, total 1,962 cc combined (advertised as 2.0L)

• Sequential Twin-Turbocharger System: Primary turbo for immediate low-RPM response (spools by approximately 2,500 RPM), secondary turbo activates around 4,500 RPM for sustained high-RPM power

• All-Aluminum Housings: Rotor housings and side housings made from aluminum for weight reduction

• Iron Rotors: Heavy-duty iron rotors with apex seals at each apex

• Two Spark Plugs per Rotor (6 total): Leading and trailing plugs per rotor for complete combustion

• Electronic Sequential Fuel Injection: Precise fuel metering for each rotor

• Liquid Cooled with Charge Air Cooling: Twin-turbo charge cooling system for sustained high-output operation

• 8,000 RPM Redline: High-revving like all Mazda rotaries

• Reliability: Known for rugged construction within the rotary engine context , properly maintained 20B engines have proven service histories in Eunos Cosmo applications

Common 20B Service Items (Honest Disclosure)

Honest disclosure of 20B-specific characteristics and considerations:

• Oil Consumption is Normal: Like all rotary engines, the 20B burns engine oil by design for apex seal lubrication. Expect 1 quart per 1,500-3,000 miles in regular service. With three rotors, oil consumption may be slightly higher than 2-rotor engines.

• Apex Seal Service: 20B apex seals (three rotors, three apex seals each, nine seals total) typically last 60,000-100,000 miles. Service is expensive due to the rare nature of the engine and limited replacement part availability.

• Sequential Twin-Turbo Complexity: The sequential twin-turbo system has many vacuum and pressure control lines that can develop leaks at high age (these engines are now 30+ years old). Common failure point is the secondary turbo control system.

• Premium Fuel Required: 91 octane minimum, 93 recommended. Never use regular gas.

• Rotary Engine Specialist Required: Service and rebuild work should ONLY be performed by qualified rotary specialists. General mechanics rarely have rotary expertise.

• Parts Rarity: Some 20B-specific parts are extremely rare and expensive (apex seals, eccentric shaft, side housings). Plan for higher parts costs than 13B service.

• Compression Critical: Compression test results are the best indicator of 20B health. Strong compression across all three rotors indicates a healthy engine.

Why Choose a Used 20B Engine?

A 20B engine purchase is a significant investment with proper consideration:

• Cost vs reman: $12,999 used vs $18,000-$30,000 reman plus core (when available)

• Rarity premium: 20B engines hold value due to limited production

• Engine swap appeal: Perfect base for an RX-7 FD or FC swap project

• Triple-rotor experience: The 20B’s signature exhaust note and power delivery are unlike any other engine

• Tuning ceiling: With supporting modifications, 500-800+ HP is achievable

• Limited supply: Eunos Cosmo production was small; 20B engines are increasingly rare

FAQs

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