Rotary engines remain a relatively uncommon choice for modern vehicles, despite their impressive advantages and the inherent coolness of the technology. Boasting fewer moving parts and a circular motion instead of the typical back-and-forth movement, these engines offer smoother operation and a lower likelihood of parts failure compared to reciprocating engines.
If you have a keen interest in rotary engines, these cars equipped with rotary engines should definitely pique your curiosity. Additionally, it’s worth noting that beyond cars, some helicopters and planes also harness the efficiency of this engine design.
Another noteworthy aspect is the compact physical size of rotary engines, which sets them apart from most reciprocating engines. This smaller size not only contributes to efficiency but also provides extra space within the vehicle for additional equipment and features.
From high-speed racing motorcycles to airplanes and even some lesser-known cars, a variety of cool and intriguing vehicles feature rotary engines, and surprisingly, they’re most affordable.
What Are Rotary Engines?
Rotary engines, also known as Wankel engines (named after their inventor, Felix Wankel), are a type of internal combustion engine distinct from the more common piston engines. Unlike conventional engines that use pistons moving up and down inside cylinders, rotary engines use a triangular rotor that rotates inside an epitrochoidal (roughly oval-shaped) housing. This design allows for a smoother and more continuous power delivery.
Key Components
- Rotor: The triangular rotor is the primary moving part within the engine. It has three convex faces, each acting like a piston in a conventional engine. The rotor’s motion is what creates the engine’s power.
- Housing: The epitrochoidal-shaped chamber in which the rotor moves. It contains the rotor and provides the space for the combustion process.
- Eccentric Shaft: This is the rotary engine’s equivalent of a crankshaft. The rotor moves around this shaft, which translates the rotor’s motion into usable power.
- Spark Plugs: Just like in a piston engine, spark plugs ignite the air-fuel mixture within the rotor’s chambers.
- Ports: Instead of valves, rotary engines use intake and exhaust ports to allow air and fuel to enter and exhaust gases to exit.
Working
The rotary engine completes the four-stroke combustion process (intake, compression, power, and exhaust) in each of its chambers. Here’s a step-by-step look at this process:
- Intake: As the rotor moves, it creates a vacuum in one of its chambers, drawing in an air-fuel mixture through the intake port.
- Compression: The rotor continues to move, compressing the air-fuel mixture in the chamber as the space within the housing decreases.
- Power: The spark plug ignites the compressed air-fuel mixture, causing an explosion that pushes the rotor, creating rotational force.
- Exhaust: The rotor moves again, expelling the burnt gases through the exhaust port as the space within the chamber increases.
Advantages
- Compact Size: Rotary engines are smaller and lighter than equivalent piston engines, making them ideal for vehicles where space and weight are critical.
- Smooth Operation: The continuous rotation of the rotor results in less vibration and smoother operation compared to the reciprocating motion of piston engines.
- High Power-to-Weight Ratio: Due to their design, rotary engines can produce a significant amount of power relative to their size and weight.
Disadvantages
- Fuel Efficiency: Rotary engines tend to be less fuel-efficient than piston engines due to their larger combustion chamber surface area, which can lead to higher fuel consumption.
- Emissions: The same large surface area also means more heat loss and less efficient combustion, leading to higher emissions of pollutants.
- Durability and Maintenance: Rotary engines can be more prone to wear and tear, especially in the seals between the rotor and the housing, requiring more frequent maintenance.
With no pistons in sight, spinning vigorously and emitting a distinctive sound like no other, the Rotary has garnered a devoted following over the decades. And why not?
While some rotary-powered vehicles might have fallen short, others emerged as masterpieces of their era. Here’s a compilation of our top 7 picks for rotary-powered vehicles.
1. Mercedes C 111
This vehicle stands out as an uncommon car not originally intended for consumer use or regular driving outside of a testing environment. The C 111 was conceived as a research project. Its distinctive stylish design and futuristic elements remain standout features, contributing to its enduring presence in our cultural awareness.
Equipped with a three-rotor Wankel engine, the C111 boasted an impressive top speed for its time, ranging from 168 to 186 mph depending on the chosen version of the vehicle.
However, the C111 faced challenges that hindered its practicality on the road, notably its inability to meet US emissions standards. Ultimately, these issues led to the discontinuation of the C111 from production.
2. Citroen GS Birotor
As previously mentioned, Citroen collaborated with NSU on rotary engine development, and this collaboration found expression in a few of Citroen’s cars, including the uniquely French GS Birotor.
Positioned as Citroen’s mid-range vehicle, the GS aimed for economic efficiency while standing out with enhanced luxury features, cutting-edge technology for its era, and a smooth driving experience.
In a departure from traditional piston engines, Citroen incorporated a 2-rotor Wankel rotary engine into the GS. While this innovation delivered impressively smooth and reasonably powerful performance, it suffered from reliability issues and excessive fuel consumption, rendering it impractical. Production of the GS Birotor spanned from 1973 to 1975, yielding only 837 units.
3. Mazda 787B
Mazda has gained recognition for its expertise in crafting vehicles equipped with rotary engines, distinguishing itself as one of the manufacturers successful in implementing this engine type across various models.
Initially conceived as a racing vehicle, the 787B faced a slower start compared to some of its competitors in the early stages of the race. However, the true strengths of this vehicle became evident later on, as it surpassed other race cars in performance during the latter part of the race.
Notably, the 787B earned a reputation for remarkable reliability, a noteworthy feat for a race car, especially considering its utilization of a rotary engine.
4. Mazda Cosmo
The Cosmo marked Mazda’s debut into the realm of rotary-engine cars and stood as the company’s flagship for an extended period. Mazda persisted with the Cosmo until it became evident that consumer interest had waned, overshadowed by the more streamlined and alluring RX-7.
Regrettably, this shift occurred despite the JC Cosmo, the final iteration, evolving into a technological marvel far ahead of its time. While the JC and early versions like the L10A/B and the CD garnered more attention, the HB Cosmo tends to fly under the radar.
Despite being less coveted than its counterparts, the HB possesses a distinct 1980s design, featuring bold interiors and the iconic pop-up headlights. Although it may not be hailed as the epitome of beauty, the HB Cosmo exudes a delightful retro charm in today’s perspective.
5. NSU Ro 80
NSU holds the distinction of being the first Western car manufacturer to produce a car powered by a rotary engine, specifically with the 1964 Spider. Unfortunately, we were unable to obtain sufficiently large images of this model.
Instead, we are showcasing a later creation, the 1967 Ro 80, a four-door sedan designed for families in the former West Germany. Equipped with the Comotor-built Wankel engine, boasting a displacement of 995cc, it delivered a robust 106bhp to the front wheels.
Over the ensuing decades, NSU was gradually integrated into Audi. However, the manufacturing facility in Neckarsulm, where these innovative vehicles were crafted, continues to be operational under Audi’s management.
Presently, the site is responsible for the production of Audi’s A4, A5, A6, A7, and A8 models, and it serves as the base for Audi Sport.
6. Citroen M35
Surprisingly, Citroen ventured into the realm of rotary engines, a fact not widely known. The French automaker crafted a mere 267 units of the Wankel-powered M35 during the brief period from 1969 to 1971.
The M35, a petite coupe, boasted a compact 995cc longitudinally-mounted rotary engine capable of generating 37kW and 68Nm. Its diminutive size earned it a charming appeal. Notably, the engine’s smooth and hushed operation led Citroen to install an alarm that would sound when the car approached the redline.
Adding to its allure, the M35 featured Citroen’s renowned hydropneumatic suspension system, ensuring the utmost comfort. — Tom Fraser.
7. Mazda RX-8
For those seeking a contemporary vehicle equipped with a rotary engine, the 2003 RX-8 presents itself as a viable option. Despite its 4-door configuration, it maintains a reputation for reliability and safety, offering an affordable choice within the realm of rotary engine vehicles.
Although production ceased in 2012, the RX-8 continues to hold up well even by today’s standards. Notably, it was introduced with a range of advanced safety features, making it a relatively secure choice for contemporary driving.
This car stands out as a distinctive option for rotary enthusiasts and serves as an appealing choice for anyone in the market for a used Mazda, irrespective of the unique engine design.
FAQ
What is a rotary engine?
A rotary engine, also known as a Wankel engine, is a type of internal combustion engine that uses a unique rotary design instead of the traditional piston-cylinder arrangement.
Which car manufacturers produce vehicles with rotary engines?
Historically, Mazda is the most notable car manufacturer associated with rotary engines. Models like the RX-7 and RX-8 featured these distinctive powerplants.
How does a rotary engine work?
Unlike traditional engines with reciprocating pistons, a rotary engine has a spinning triangular rotor that completes the four-stroke combustion process within a chamber, resulting in continuous, smooth rotation.
What are the advantages of a rotary engine?
Rotary engines are known for their compact size, high power-to-weight ratio, and smooth operation. They also produce fewer vibrations compared to traditional piston engines.
Final Thought
Cars with rotary engines are known for their unique design, featuring a spinning triangular rotor instead of traditional pistons. Mazda, notably with models like the RX-7 and RX-8, has been a key player in popularizing this distinctive engine type.
While appreciated for their compact size and smooth operation, rotary engines also come with challenges, including potential maintenance complexities and historically, emission concerns.
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