20B Engine – From 13G Racing to 20B-REW Production Rotary Engines

[Zack Norman]

Rotary engines, particularly the 20B engine, offer a unique driving experience, distinct from conventional piston engines due to their design, leading to inherently lower torque. Mazda's solution to this challenge was forced induction, significantly improving the engine's output. The 13B engines, despite their popularity, especially in models like the RX8, often leave enthusiasts craving more power due to their modest torque output. This has led to a significant aftermarket industry focused on enhancing the power of these engines through various modifications, including forced induction kits.

The discussion around engine displacement is crucial when addressing the low-end torque issue. Increasing the rotor count within a rotary engine is equivalent to adding more cylinders in a piston engine, which Mazda explored with their prototypes, like the 4-rotor 26B used in the 787B for the 24 Hours of Le Mans, marking a historic win with a non-piston engine.

The 20B rotary engine, less known than the 26B, found its place in the Mazda 767B and was deemed a good balance of power, reliability, and cost by Mazda. This led to its use in the mass-production road car, the JC Eunos Cosmo, the only 3-rotor drivetrain vehicle produced for the road.

The Eunos Cosmo highlighted Mazda's engineering prowess, offering luxury features alongside its powerful 20B-REW engine, capable of producing 300 horsepower and 403 Nm of torque. Despite being sold with a 4-speed automatic transmission, it distinguished itself from the RX7, offering a smooth and powerful driving experience.

Mazda's 20B engines, including the 13G racing engines and the 20B-REW, demonstrate the versatility and potential of rotary engines for both racing and road use. The 20B-REW, in particular, is sought after for its balance of power and smoothness, making it a favorite among enthusiasts for engine swaps in RX7 or RX8 models. However, sourcing a 20B-REW can be challenging and expensive, given its exclusivity to the JC Eunos Cosmo and its production solely in Japan.

The evolution of the 20B engine from racing prototypes to a mass-produced version underscores the ongoing interest in rotary engines within the automotive enthusiast community. Despite challenges such as maintenance costs and the complexity of modifications, the 20B engine remains a coveted choice for those seeking a unique driving experience with the distinct sound and performance characteristics of a rotary engine.

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