Rotaries can be exhilarating to drive, but they have a notorious reputation for being unreliable. Whether you’re behind the wheel of a Mazda RX-7 or any other rotary-powered vehicle, you’re sure to encounter a range of issues that can leave you stranded on the side of the road. The reason why rotaries are unreliable goes beyond the typical wear-and-tear of a high-performance engine. There are inherent flaws in the rotary design that make it vulnerable to failure.
For starters, rotaries are notorious for burning oil. Unlike traditional piston engines, rotaries use a unique Wankel design that relies on triangular rotors instead of pistons. This design inherently leads to oil consumption, which can cause a range of problems over time. Additionally, the unique design of rotaries requires tight tolerances between the components, which make them susceptible to damage from overheating, detonation, and other issues.
Despite these challenges, rotary enthusiasts remain dedicated to this unique engine design. They’re willing to overlook the flaws and take on the challenges of keeping a rotary-powered vehicle running reliably. And for those who do manage to maintain their rotaries, there’s nothing quite like the thrill of driving an engine that is as unique as it is challenging. Whether you love them or hate them, there’s no denying that rotaries are one of the most polarizing engines on the road.
Rotary engine types
When it comes to rotary engines, there are three main types that are commonly used in automobiles:
- Single-rotor engines
- Two-rotor engines
- Three-rotor engines
Single-rotor engines are the simplest form of a rotary engine, with only one combustion chamber. This results in lower power output and lower fuel efficiency than the other two types. Two-rotor engines are the most common and are often found in sports cars and high-performance vehicles. They offer good power output and fuel efficiency, but can still suffer from reliability issues due to their unique design. Three-rotor engines are the most powerful and efficient of the three types, but are also the most complex and expensive to produce.
Rotary engine design
The rotary engine, also known as the Wankel engine, is a unique design that differs from traditional reciprocating engines. The engine was developed in the 1950s by a German engineer named Felix Wankel and was introduced in the Mazda RX-7 in the 1970s. The rotary engine design is known for its lightweight and compact design, as well as its smooth and rev-happy power delivery.
- The rotary engine operates on a triangular rotor that rotates inside an oval-shaped housing called the stator. The rotor has three sides, which create three separate chambers as it rotates.
- The motion of the rotor compresses the air and fuel mixture, which is ignited by a spark plug, generating power in each chamber.
- The rotor continues to rotate, creating three power strokes for each rotation, resulting in a high power-to-weight ratio and smooth power delivery.
Why are rotaries unreliable
Although the rotary engine has numerous benefits, it is notorious for being unreliable. The unique design of the engine leads to several issues that can cause it to fail prematurely. Here are some reasons why the rotary engine is unreliable:
- Apex seals: The most common issue with rotary engines is the apex seals, which seal the combustion chamber. The seals are under constant heat and pressure, leading to wear and tear over time, resulting in poor compression and loss of power.
- Oil consumption: Another issue with rotary engines is their high oil consumption. The engine burns oil as part of the combustion process, causing excessive oil use and potentially leading to engine failure if the oil level isn’t regularly checked and maintained.
- Overheating: The rotary engine runs at high temperatures and can be prone to overheating. If the engine runs too hot, it can cause premature wear and tear, leading to engine failure.
Additionally, the unique design of the engine makes it challenging to repair and maintain, as it requires specialized knowledge and parts. This leads to high repair costs and a limited number of qualified mechanics who can work on the engine.
| Pros | Cons |
|---|---|
| Compact and lightweight design | High oil consumption |
| Smooth power delivery | Overheating issues |
| High power-to-weight ratio | Apex seal failures |
Despite its drawbacks, the rotary engine is still popular among automotive enthusiasts who appreciate its unique design and smooth power delivery. However, to ensure longevity, owners of rotary engine vehicles must be diligent in their maintenance and regularly check for any signs of wear and tear.
Lack of Fuel Economy
One of the most significant drawbacks of rotary engine cars is their poor fuel economy. Rotaries have a reputation for being thirsty, which is one of the reasons why they are not as commonly used in cars as traditional piston engines.
There are several reasons why rotaries are less fuel-efficient, including:
- High RPMs: The rotary engine operates at much higher RPMs than a traditional piston engine. The faster the engine runs, the more fuel it consumes. This means that rotaries require more fuel to produce the same amount of power compared to a piston engine.
- Less Efficient Combustion: In a rotary engine, the fuel-air mixture is compressed and ignited within a small cavity, which isn’t as efficient as the combustion process in a piston engine. This results in a less efficient use of fuel, and therefore, lower fuel economy.
- Less Time Spent in the Ideal RPM Range: Rotaries are notorious for not producing torque at low RPMs, which means they must be revved up to their higher RPM range to get the most power. However, this results in the engine spending less time in the ideal RPM range for fuel efficiency, which leads to less fuel economy.
In addition to these factors, rotary engines tend to suffer from poor sealing, which can lead to fuel consumption and a lack of fuel efficiency. The rotor seals in a rotary engine tend to wear out faster than the piston rings in a traditional piston engine, which results in more internal leakage and a decline in fuel efficiency.
| Model | MPG (City) | MPG (Highway) |
|---|---|---|
| Mazda RX-8 | 16 mpg | 22 mpg |
| Mazda RX-7 | 15 mpg | 23 mpg |
| Mazda Cosmo | 12 mpg | 20 mpg |
As the table shows, most rotary engine cars get significantly worse fuel economy compared to traditional piston engine cars. This is due to the reasons mentioned above, making rotaries unreliable in terms of gas mileage.
High Emissions
One of the biggest drawbacks of rotary engines is their high emissions. Due to their design, rotary engines tend to produce more pollution than traditional piston engines. Here are some reasons why:
- Unburned fuel – Rotaries have a tendency to emit more unburned fuel than piston engines. This is because the fuel does not have enough time to completely burn before it is expelled from the exhaust.
- Poor fuel economy – Because rotary engines have a higher fuel consumption rate than piston engines, they produce more emissions per mile driven.
- Increased NOx – Rotaries tend to produce more oxides of nitrogen (NOx) than piston engines due to their high combustion temperatures. NOx is a major contributor to smog and respiratory problems.
As a result of their high emissions, rotary engines have fallen out of favor with regulators in many countries. In fact, Mazda discontinued the RX-8 rotary sports car in part due to its inability to meet emissions regulations in some markets.
Shorter lifespan
One major reason why rotaries are considered unreliable is their shorter lifespan compared to traditional piston engines.
The main reason for this is the unique design of the rotary engine, with its spinning triangular rotor that creates a lot of internal heat and pressure. This puts a lot of stress on the engine components, which can wear out and fail more quickly than in a piston engine. Additionally, the highly engineered tolerances required for optimal performance also mean that any small issues can quickly spiral into major problems.
- Rotary engines have a tendency to consume oil, which can lead to dirty and clogged engine components over time.
- The apex seals, which maintain pressure and prevent leakage between the combustion chamber and the oil system, are a weak point of rotary engines and can fail easily, leading to major engine damage.
- The unique design of rotary engines also means that they require more frequent maintenance and specialized expertise to repair, which can be time-consuming and expensive.
Overall, while rotary engines have some unique advantages, their shorter lifespan and higher maintenance requirements make them less practical for everyday use and more suited to specialized applications where their capabilities can be fully utilized.
| Pros | Cons |
|---|---|
| High power-to-weight ratio | Shorter lifespan compared to traditional engines |
| Smooth operation | Higher maintenance requirements |
| Higher RPM capabilities | Limited availability of parts and expertise |
While the pros of rotary engines are certainly impressive, their cons cannot be overlooked, and they may not be the best option for those seeking a reliable and durable engine. As with any type of engine, it is important to carefully consider your needs and priorities before making a decision.
Difficulty with Repairs
Rotaries are known for their unique design and performance, but this also means that they are more complicated to repair than traditional engines. Here are some of the reasons why:
- Rotaries have a simpler design in some ways, such as fewer moving parts, but this also means that a single problem can affect multiple systems. As a result, repairs can be more time-consuming and costly.
- The design of the rotary engine creates some challenges when it comes to diagnosing and fixing problems. For example, disassembling the engine to access certain components can be difficult, requiring specialized tools and expertise.
- Rotary engines have a reputation for being sensitive to maintenance and parts quality. Using the wrong type of oil, for example, can cause damage and lead to costly repairs.
Additionally, because rotary engines are relatively rare, finding a mechanic with experience working on rotary engines can be challenging. This can add to the time and expense of repairs, particularly if you need to travel to find a specialist.
Here is an example of how this can play out in practice. Imagine that your rotary engine is making an unusual noise. A mechanic who is unfamiliar with rotary engines may misdiagnose the problem and replace the wrong component. This can lead to further damage, and you may need to bring the car to a specialist rotary mechanic to fix the original problem as well as the new issues created by the misdiagnosis.
| Difficulty with Repairs | Why |
|---|---|
| Specialized tools needed | Disassembly can be difficult |
| Sensitivity to maintenance and parts quality | Using the wrong oil or parts can cause damage |
| Mechanics with experience are hard to find | Can be time-consuming and expensive to locate a specialist |
In summary, while rotary engines offer unique benefits in terms of performance and design, they also have some drawbacks when it comes to repairs. Rotary engines require specialized knowledge, tools, and parts, which can make repairs more challenging and expensive than for traditional engines.
Increased Maintenance Costs
One of the main reasons why rotaries are often considered unreliable is the high maintenance costs associated with them. Rotaries tend to have a shorter lifespan than other engine types, which means they require more frequent maintenance and repairs to keep them running smoothly. Here are some of the reasons why rotaries require more maintenance:
- Seals and Bearings: The seals and bearings in the rotary engine are designed to withstand a lot of heat and pressure, but they can wear down quickly and need to be replaced more frequently than in other engine types.
- Oil Consumption: Rotary engines tend to burn more oil than other engine types. This means that owners need to keep a closer eye on oil levels and perform more frequent oil changes to avoid damaging the engine.
- Cooling System: The cooling system in rotary engines is often complex and can be prone to leaks or other problems. Regular maintenance is necessary to keep the cooling system working properly and prevent overheating.
Overall, the increased maintenance costs associated with rotaries can make them a less appealing option for some car enthusiasts. However, for those who are willing to invest in the necessary maintenance and repairs, a rotary engine can still provide a unique driving experience that is hard to find with other engine types.
FAQs: Why are Rotaries Unreliable?
1. What causes a rotary engine to be unreliable?
Rotary engines are known for their unique design, which can lead to a variety of issues that make them less reliable than other types of engines. The engine’s seals and Apex seals, in particular, are prone to wear and tear, which can result in compression loss and damage to the engine’s rotors.
2. Are rotary engines more expensive to maintain than other engines?
Yes, rotary engines can be more expensive to maintain than other types of engines, due to their unique design and the need for special parts. In addition, rotary engines are often more difficult to work on, which can also increase maintenance costs.
3. Why do rotary engines have a reputation for not lasting as long as other engines?
Rotary engines have a tendency to wear out faster than other types of engines, due to the high RPMs they run at and the stresses placed on their unique design. This can lead to reduced engine life and increased likelihood of failure.
4. Can rotary engines be made more reliable?
Yes, there are steps that can be taken to increase the reliability of a rotary engine, such as using higher-quality seals and Apex seals and performing regular maintenance. However, these steps can be costly and may not completely eliminate the issues associated with rotary engines.
5. Is it worth buying a car with a rotary engine?
It depends on your priorities and preferences. While rotary engines are known for their unique sound and performance capabilities, they are also less reliable and more expensive to maintain than other types of engines. If you value performance and are willing to deal with the potential maintenance issues, a rotary engine may be a good choice for you.
6. What are some common problems associated with rotary engines?
Common problems with rotary engines include compression loss, Apex seal failure, and oil leaks. These issues can result in reduced engine performance, increased exhaust emissions, and engine failure if not addressed.
7. Are there any benefits to having a rotary engine?
Yes, rotary engines are known for their high-revving capabilities, lightweight design, and unique sound. They also have a simpler design than other types of engines, which can make them easier to work on in certain cases.
Closing Thoughts: Thanks for Reading!
Rotary engines are a unique breed of engine that offer a high-revving, high-performance experience but can also be notoriously unreliable. While there are steps that can be taken to increase their reliability, owning a car with a rotary engine comes with its own set of challenges. Whether you’re a diehard rotary fan or just curious about this engine type, we hope this article has been informative. Thanks for reading, and please visit again soon for more automotive content!