How does Rotary engine (Wankel engine) Work

Crafted by Felix Wankel, the Wankel rotary engine is a departure from conventional piston engines, boasting unusual designs that eliminate the need for complex mechanisms. Unlike the two-stroke,four-stroke cycle of a piston engine with its myriad of moving parts, the rotary engine simplifies the process. It features a triangular rotor housed within oval-like housings, with curved sides creating an epitrochoid shape. This configuration negates the necessity for valves, timing gears, con-rods, pistons, and crankshaft, reducing the number of moving parts significantly.

Fuel and air enter the intake port as the rotor spins, moving through pinched-in sides during compression. The combustion stroke occurs as the mixture ignites, generating power directly on the output shaft. 

This streamlined process ensures a continuous flow of combustion events, delivering power without the interruption of reciprocal motion found in a traditional combustion engine. With fewer components and simplified mechanics, the Wankel engine achieves impressive rpm and power output, revolutionizing the landscape of motor vehicles with its efficient and innovative design.

Rotary Engine Work

Rotary engines, famously known as Wankel engines, possess an inherent eccentric design that sets them apart from conventional piston engines. The cylindrical shape of the rotor defines its operation. Unlike traditional engines, the rotary engine accomplishes the four-stroke cycle within a single revolution of its rotor. This streamlined process eliminates the reciprocating motion of pistons found in typical engines, resulting in smoother operation with fewer moving parts.

Inside the Wankel Engine

When delving into the intricacies of the Wankel engine, one is immediately drawn to its innovative design. At its heart lies a unique component: the rotor. Resembling a three-sided piston, this rotor revolves within a rotor housing. This housing, along with an endplate, forms a chamber with curved lobes, akin to a figure of eight.

During operation, the rotor undergoes a continuous rotation, creating a cycle that enables the engine to generate power. The combustion process occurs within this chamber, where a fuel-air mixture is timed and ignited by a spark plug. As the gasses expand, they exert force on the rotor, propelling it forward.

This rotary motion replaces the conventional reciprocating motion found in traditional piston engines. Consequently, the output shaft receives power impulses without the need for pistons, crankshafts, or complex gearing systems. This streamlined design not only reduces vibrations but also ensures smooth-running performance.


The journey of the Wankel engine is as fascinating as its operation. Conceived by Felix Wankel, the idea gained appeal during World War Two, when Wankel began researching compressors. Post-war, he teamed up with NSU, a German car manufacturer, to realize his vision of a practicable internal combustion engine.

The culmination of this partnership was the NSU Wankel Spyder, a small rear-engined sports car that captured the public’s imagination. With its twin-rotor engine, the Spyder boasted impressive performance figures, including a top speed of 110mph. This achievement solidified the success of the rotary engine concept and garnered widespread acclaim.

As the technology advanced, modern Mazda cars became synonymous with Wankel engines, showcasing the continuous development and refinement of this groundbreaking innovation. Today, the legacy of Felix Wankel lives on in the smooth power delivery and distinctive engine note of Mazda’s rotary-powered vehicles.


A notable departure from traditional reciprocating engines lies in the design of the Wankel engine. Instead of valves, the engine relies on ports within the rotor housing and endplate for intake and exhaust. This compact arrangement eliminates the need for ancillaries like a starter, generator, and cooling system, resulting in a lighter and more efficient power plant.

Moreover, the absence of reciprocating components such as camshafts, pushrods, and rockers further reduces weight and complexity. The result is a powertrain that excels in terms of installation flexibility, vibration mitigation, and overall reliability.

In vehicles like the NSU Ro80, the smooth-running characteristics of the Wankel engine are especially pronounced, offering a driving experience free from the inherent vibrations of traditional piston engines. With balanced rotors and housings, coupled with precise timing and fuel delivery, the Wankel engine continues to stand as a testament to ingenuity and engineering excellence.

Principles of a Rotary Engine

  • Operation based on rotational motion, not reciprocating.
  • Utilization of a triangular rotor within a combustion chamber.
  • Pressure and forces drive the rotor’s continuous cycle.
  • Expansion and contraction of gas volumes for combustion.
  • Efficient conversion of combustion energy into rotational motion.
  • Reduction in moving parts, vibrations, and noise.

Mazda RX-8

  • Mazda’s pioneering role in rotary engine technology.
  • Success of the RX-8 as a prime example of rotary-powered cars.
  • Achievement of International Engine of the Year award in 2003.
  • Performance of the naturally aspirated, two-rotor engine.
  • Balanced design for exceptional handling and driving experience.
  • Personal experience as a Mazda RX-8 owner.
  • Information available on Mazda’s website about the RX-8 and its rotary engine.

The Parts of a Rotary Engine

The Rotary engine, also known as the Wankel engine, is a marvel of engineering ingenuity. Its design deviates from the conventional piston engine, offering a surprise with its unique approach to combustion. Understanding its intricacies starts with dissecting its core components.

Rotor: The Heart of the Rotary Engine

At the center of the rotary engine lies the rotor, akin to the piston in a traditional engine but with a distinct configuration. Shaped like a triangular prism, the rotor revolves within an oval housing, its metal blade-lined faces traversing a precise path dictated by internal gear teeth. This motion creates pockets where the air/fuel mixture resides, ready for ignition in the combustion chamber.

Housing: Embracing the Rotor’s Dance

Surrounding the rotor is the housing, sculpted in an epitrochoid shape to accommodate the rotor’s movements. This housing forms the walls of the combustion chamber and ensures sealed volumes as the rotor rotates. Through a carefully orchestrated intake, compression, combustion, and exhaust cycle, the housing guides the flow of gas with minimal contact resistance, optimizing efficiency.

Output Shaft: Translating Rotation into Power

As the rotor pirouettes within its housing, it imparts force onto the output shaft. This shaft, positioned off-center and eccentric to the rotor’s centerline, translates the rotor’s rotational spin into usable power. Unlike the linear motion of a piston engine, the output shaft follows a circular path, generating torque that drives the assembly forward with remarkable smoothness.

Crafting the narrative of how a Rotary engine operates is akin to unraveling a mystery, each component playing its role in harmony to deliver performance that defies recognition.

Rotary Engine Assembly

Assembled with precision, the Rotary engine reveals a fascinating complexity hidden beneath its seemingly simple facade. Picture layers of intricate machinery, meticulously pieced together to form a symphony of motion. At its heart lies the two-rotor design, a marvel of engineering ingenuity. These rotors, akin to the beating heart of the engine, rotate within the housing, their surfaces smooth as silk.

Coolant flows through passageways, ensuring optimal operating temperatures, while seals and bearings maintain the integrity of the assembly. The main ring bolts secure the sections together, creating a robust structure that houses the essence of power. Within this housing, the magic unfolds. The intake port, oval-shaped and purposeful, welcomes the air-fuel mixture into the heart of the machine, while the exhaust ports stand ready to release spent gases.

Rotary Engine Power

In understanding the power behind rotary engines, one delves into the essence of motion itself. Unlike traditional piston engines, rotary engines operate on a four-stroke combustion cycle but with a twist. The rotor, akin to a piston but with a circular lobe offset from the output shaft, is the catalyst for motion. As the rotor orbits within the housing, it undergoes the essential strokes: intake, compression, combustion, and exhaust.

With each revolution, the combustion strokes drive the output shaft into a frenzied dance, spinning with purpose and vigor. This spinning motion translates into power, propelling vehicles forward with a relentless determination. It’s akin to a carefully orchestrated dance, where every movement contributes to the overall spectacle. And just like a well-tuned winch, the rotary engine leverages its design to maximize efficiency and output.

Differences and Challenges

When comparing rotary engines to their piston counterparts, several differences emerge, each presenting its own set of challenges and opportunities. One notable dissimilarity lies in the number of moving parts. While piston engines rely on an intricate web of pistons, connecting rods, and camshafts, rotary engines boast a simpler configuration, with fewer components to manage.

This reduction in moving parts not only translates to smoother operation but also enhances reliability, a crucial factor in industries such as aviation where every component must function flawlessly. However, this simplicity comes with its own set of challenges, particularly in designing components that comply with stringent emissions regulations and optimizing thermodynamic efficiency to minimize fuel consumption.

Despite these challenges, the allure of rotary engines persists, captivating the imaginations of enthusiasts and engineers alike. With each revolution, they offer a glimpse into a future where power and efficiency coexist harmoniously, driving innovation ever forward.


In conclusion, the Wankel rotary engine stands as a testament to innovation and efficiency in the realm of internal combustion engines. Crafted by Felix Wankel, this revolutionary design simplifies the combustion process by utilizing a rotating triangular rotor within an oval housing, eliminating the need for numerous moving parts found in traditional piston engines.

 With its streamlined operation and fewer components, the Wankel engine achieves impressive power output and rpm, offering a smoother and more efficient alternative to conventional engines. From its inception during World War Two to its integration into modern Mazda vehicles, the Wankel engine continues to redefine the landscape of motor vehicles, showcasing the enduring legacy of ingenuity and engineering excellence.


What are the steps of a Wankel engine?

In a Wankel engine, one side of the triangular rotor completes the four-stage Otto cycle of intake, compression, expansion, and exhaust each revolution of the rotor.

What is the principle of a rotary engine?

rotary engine, internal-combustion engine in which the combustion chambers and cylinders rotate with the driven shaft around a fixed control shaft to which pistons are affixed; the gas pressures of combustion are used to rotate the shaft.

What is the difference between a rotary engine and a Wankel engine?

A Wankel is a type of rotary engine. It uses a large rotating mass as a piston to create the power. Piston driven rotary engines use a circular array of pistons to drive a crank. Those are like the engines you see on prop driven airplanes.

Why is it called a Wankel engine?

The rotary-engine (also known as the Wankel-engine) is an alternative to the classic piston-engine, developed in 1954 by the German mechanical engineer Felix Heinrich Wankel. Wankel’s main motivation was to create an engine that wouldn’t have the strong vibrations of a piston engine.

What is the purpose of the Wankel engine?

Rotary engines or Wankel engines are a type of internal combustion engine, most popularly used in the Mazda RX-7, which converts heat from the combustion of a high pressure air/fuel mixture into useful work for the rest of the car.

Why are rotary engines fast?

There are no valves in a rotary engine, which is a major reason a rotary has roughly 75% fewer moving parts than a piston engine. The lack of a valvetrain and less rotating mass allow a Wankel to rev more freely and to higher speeds, with some able to hit 10,000 rpm