A Wankel engine, also known as a rotary engine, is an internal combustion engine that uses a rotary design instead of conventional pistons. Developed by Felix Wankel in the 1950s, this engine features a unique triangular rotor that rotates within an oval-shaped housing. The Wankel engine is known for its compact size, high power-to-weight ratio, and smooth operation due to the continuous rotary motion, which eliminates the reciprocating parts found in traditional piston engines. This design offers several advantages but also presents unique challenges in terms of durability and fuel efficiency.

A Wankel engine works by using a triangular rotor that rotates within an oval-shaped housing. As the rotor turns, its three apexes maintain continuous contact with the housing, creating three separate combustion chambers. Each chamber undergoes the four stages of the combustion cycle—intake, compression, power, and exhaust—as the rotor completes its rotation. This rotary motion allows for a more compact and lightweight engine design compared to traditional piston engines, with fewer moving parts, leading to smoother operation and a higher power output relative to engine size.

The Wankel engine's rotary design differs significantly from traditional piston engines. Instead of pistons moving up and down, a Wankel engine uses a triangular rotor that rotates within an oval housing. This design eliminates the reciprocating motion of pistons, reducing vibration and allowing for a more compact, lightweight engine. The continuous rotary motion also simplifies the engine's structure, with fewer moving parts, leading to smoother operation. However, the unique design can present challenges, such as higher emissions and potential issues with rotor seal durability compared to piston engines.

Wankel engines offer several advantages over traditional piston engines, including a compact and lightweight design, which allows for better vehicle packaging and a higher power-to-weight ratio. The rotary motion of the engine provides smoother operation with fewer vibrations, and the simplicity of having fewer moving parts leads to potentially lower manufacturing costs. Additionally, Wankel engines can produce high power output from a smaller displacement, making them ideal for applications where space and weight are critical. However, these benefits are offset by challenges in fuel efficiency, emissions, and long-term durability.

The lifespan of a Wankel engine can vary, but it is typically shorter than that of traditional piston engines, with major overhauls often required between 80,000 to 120,000 miles. The primary limiting factor is the durability of the apex seals, which are crucial for maintaining compression within the engine. These seals are subject to significant wear due to the continuous rotary motion and high temperatures, leading to potential loss of compression and power over time. Proper maintenance, including timely replacement of seals and careful monitoring of oil levels, can help extend the engine's lifespan.

Common issues with Wankel engines include apex seal wear, which can lead to compression loss and reduced engine performance. These seals are crucial for maintaining the engine's efficiency but are prone to wear due to the high temperatures and stresses involved in the rotary motion. Additionally, Wankel engines tend to have higher oil consumption and may suffer from poor fuel efficiency and higher emissions compared to traditional piston engines. Cooling can also be a challenge, as the unique design requires careful management of engine temperatures to prevent overheating and maintain reliability.

Wankel engines are no longer produced in large volumes for mainstream vehicles, but they are still in development and used in niche applications. Mazda, the most well-known manufacturer of Wankel engines, discontinued the RX-8, its last Wankel-powered car, in 2012 due to emission challenges. However, Mazda has continued to explore the potential of rotary engines for hybrid and range-extender applications. In aviation, small Wankel engines are still used in some light aircraft and drones, valued for their compact size and power-to-weight ratio.

Apex seals are critical components in a Wankel engine, located at each corner of the triangular rotor. These seals maintain contact with the inner surface of the engine housing, ensuring that the combustion chambers are properly sealed during each phase of the rotary cycle—intake, compression, power, and exhaust. Apex seals prevent the escape of gases, maintaining compression and engine efficiency. However, they are subject to significant wear due to the constant friction and high temperatures, making them a common point of failure in Wankel engines, often requiring periodic replacement.

The Wankel engine was invented by German engineer Felix Wankel in the 1950s. Its first commercial application was in the 1960 NSU Wankel-Spider. Mazda adopted the technology in the 1960s, becoming the most prominent manufacturer of rotary engines. Mazda's RX series, particularly the RX-7 and RX-8, popularized the Wankel engine for its compact size and high-revving nature. Despite its advantages, challenges such as fuel efficiency and emissions limited its widespread adoption. Production of Wankel-powered cars ended in 2012, but research continues, particularly for hybrid and range-extender applications.

The triangular rotor in a Wankel engine is the heart of its unique rotary design. As it rotates within the oval-shaped housing, the rotor's apexes maintain constant contact with the housing's inner surface, creating three separate chambers. These chambers go through the four stages of the combustion process—intake, compression, power, and exhaust—as the rotor completes each rotation. The rotor's shape and motion allow for continuous and smooth power delivery, unlike the intermittent power strokes of traditional piston engines, contributing to the Wankel engine's distinctive performance characteristics.

Wankel engines are renowned for their compact size and high power output relative to their displacement. The rotary design allows the engine to be smaller and lighter than traditional piston engines, making it easier to package within a vehicle. Despite their small size, Wankel engines can produce significant power due to the continuous rotary motion, which provides a more consistent and smoother power delivery. This high power-to-weight ratio makes Wankel engines ideal for applications where space and weight are critical, such as in sports cars, motorcycles, and light aircraft.

The Wankel engine's compact design offers significant benefits for vehicle packaging. Its small size and low weight allow it to be positioned lower in the chassis, improving the vehicle's center of gravity and handling dynamics. The engine's compactness also frees up space within the engine bay, providing more room for other components, such as cooling systems, turbochargers, or hybrid-electric components. This space efficiency is particularly valuable in sports cars and other high-performance vehicles, where maximizing power-to-weight ratio and optimizing handling are crucial.

The key components of a Wankel engine include the rotor, housing, and apex seals. The rotor is a triangular-shaped part that rotates within the oval housing, creating three chambers that undergo the combustion cycle. The housing contains the rotor and features an inner surface that the rotor's apexes contact, forming the combustion chambers. Apex seals, located at the corners of the rotor, are crucial for maintaining the seal between the rotor and housing, preventing gas leaks and ensuring efficient combustion. Other important components include the eccentric shaft, which converts the rotor's motion into usable power.

Wankel engines manage fuel intake and combustion differently from piston engines due to their rotary design. In a Wankel engine, the fuel-air mixture is drawn into the engine as the rotor rotates, filling one of the three chambers formed by the rotor and housing. As the rotor continues its rotation, the chamber compresses the mixture, which is then ignited to produce power. The exhaust gases are expelled as the rotor moves to the next phase. This continuous rotary motion creates a more even power delivery compared to the intermittent combustion cycles in piston engines, enhancing smoothness and responsiveness.

Wankel engines have been used in various automotive and aviation applications. In the automotive industry, they gained prominence in Mazda's RX series, including the RX-7 and RX-8, where their compact size and high-revving nature were prized for sports car performance. In aviation, Wankel engines have been used in light aircraft and drones, where their high power-to-weight ratio and compact design offer advantages in space-constrained environments. Despite their niche use, Wankel engines have remained popular in applications where size, weight, and smooth power delivery are critical factors.

The Wankel engine's design presents challenges in fuel efficiency and emissions. The rotary motion and the large surface area of the combustion chamber can lead to incomplete combustion, resulting in higher fuel consumption and increased emissions compared to piston engines. Additionally, the apex seals can allow some fuel to escape during the combustion process, further reducing efficiency. These factors, combined with the difficulty in meeting modern emission standards, have limited the widespread use of Wankel engines in mainstream vehicles, despite their advantages in size and power output.

Maintaining and servicing Wankel engines can be challenging due to their unique design. The apex seals, crucial for maintaining compression, are prone to wear and require periodic replacement, which can be labor-intensive and costly. The rotary design also demands specialized knowledge and tools for effective servicing. Additionally, the engine's higher oil consumption necessitates more frequent oil checks and changes. Cooling and lubrication systems must be carefully monitored to prevent overheating and ensure long-term reliability. These factors contribute to higher maintenance costs and complexity compared to traditional piston engines.

The Wankel engine's unique combustion process can impact its reliability and longevity. The rotary motion leads to uneven heat distribution and higher stress on the apex seals, which are essential for maintaining compression and preventing gas leaks. Over time, these seals wear down, leading to reduced performance and potential engine failure. The engine's higher operating temperatures and oil consumption can also contribute to accelerated wear of internal components. While Wankel engines offer smooth and powerful performance, their longevity is often shorter than traditional piston engines, with frequent maintenance required to ensure reliability.

Wankel engines require specialized cooling and lubrication due to their rotary design and high operating temperatures. The cooling system must be effective to prevent overheating, often employing a combination of liquid and air cooling. The unique engine geometry necessitates careful management of heat distribution. For lubrication, Wankel engines use a high-capacity oil system to ensure adequate lubrication of the rotor and apex seals. Specialized oil formulations help to reduce wear and maintain proper engine function. Regular maintenance is crucial to manage oil consumption and ensure the longevity of the engine.

Sachs rotary engines were primarily used in small motorcycles and light aircraft. Notably, the Sachs 186 engine powered the renowned Zündapp KS 175 motorcycle and other models. These engines are characterized by their compact design and low weight, making them ideal for applications requiring efficiency and power in a small package. Sachs rotary engines were known for their simplicity and reliability, contributing to their popularity in the motorcycle industry during the mid-20th century, especially in Europe.

The Wankel rotary engine is an internal combustion engine that uses a rotary design to convert pressure into rotating motion. Instead of traditional pistons moving up and down, the Wankel engine features a triangular rotor that orbits within an epitrochoidal housing. This design results in fewer moving parts, a compact size, and smooth operation, leading to high power-to-weight ratios. Although Wankel engines are renowned for their performance and unique engineering, they often face challenges with fuel efficiency and emissions compared to conventional piston engines.

The Mazda Wankel engine is commonly referred to as the "Mazda Renesis." This engine is an evolution of the original Wankel design and is notable for its use in the Mazda RX-8 sports car. The Renesis engine features improvements such as a revised intake and exhaust system, enhancing power output and efficiency while reducing emissions. Known for its smoothness and high-revving nature, the Renesis exemplifies Mazda's commitment to innovative rotary technology, making it a unique offering in the automotive market.