Mazda (RX7) Rotary Engine Problems: Is The Engine Reliable?

Why are Mazda Rotary engines bad? Find the answer through my in-depth guide

Popularly known as the Wankel engine, the Mazda Rotary 13B engine is such a reliable one if properly maintained. Launched initially in 1973, you will hardly find an engine of this type around, having spent more than four decades in existence.

However, despite its wide adoption, users have complained about a few things relating to the functionality of the engine.

Here are the most common Mazda Rotary 13B REW engine problems:

  1. Catalytic Converter Problem
  2. Cracked Turbo Manifold Problem
  3. Excessive Oil Consumption

Before I start discussing these problems, it is pertinent that I remind you that the Mazda Rotary 13B engine is one of the engines you can rely on with regular maintenance. However, all engines, at one point during their lifetime, develop faults due to age or other factors.

I will, however, be explaining the common problems of these engines, the signs, and symptoms to watch out for, including how to fix these problems in this article.

What Are The Most Common Mazda Rotary Engine Issues?

1. Catalyst Converter Problem

The Mazda Rotary 13B’s converter sits between the engine and the exhaust muffler. The engine runs on two catalytic converters and the first one is found within the downpipe, while the other second “main” unit is found after the first one.

Generally, engines produce emissions, especially aged ones. Thanks to the 13B rew catalytic converter that ensures it reduces these emissions for environmental safety.

Since the twin-turbo system is prone to generating heat from the engine excessively, the first catalytic converter burns up while also clogging up the main catalytic converter.

Due to this effect, the exhaust airflow will not be prevented, causing the air to return into the engine, as well as increasing the engine temperature exhaust gas temps (EGT’s). Once this happens, it makes the catalytic converter become worse and will cause the engine to produce higher emissions.

The foremost sign you will notice about clogged main is a high level of EGT’s. While it can make the engine’s internal temperature rise, it can also shut the engine down indefinitely. Some users try to prevent these issues by installing a catless downpipe.

Apparently, we can agree as we’ve noted that the catalytic converter issue is not fundamentally design related. The natural question to ask is: what is responsible for a failing catalytic converter of the Mazda Rotary 13B REW engine problem?

We’ll find out in the next sub-topic below:

What Causes Catalytic Converter To Fail

  • Malfunctioning Oxygen Sensor: If the catalytic converter of your engine is failing to do its job, it’s likely that the oxygen sensor is not functioning properly. The sensor is responsible for taking and sending exhaust gasses.
    However, once it becomes faulty, the oxygen sensor will only send the wrong readings to the vehicle computer. The remote consequence is excessive or lean fuel mixture.
    If you have the fuel mixture too rich, the catalyst can meltdown; if it’s too lean, the catalyst won’t do its job. Your vehicle won’t pass the emission test once a lean or rich mixture condition occurs.
  • Incomplete Combustion: Sometimes you’ll notice that unburned fuel gets its way into the exhaust system. The consequence is a bad catalytic converter. The entire fuel in your vehicle is supposed to completely burn up in the combustion chamber.
    Unburned fuel escapes from the chamber into the exhaust system and then into the catalytic converter. Once it gets to the converter, the fuel can ignite, leading to an overheated converter. When this happens, the converter will meltdown and get bad.
  • Clogged Exhaust System: The presence of oil or antifreeze in the exhaust system forms some carbon deposits. These deposits create some blockade in the way of the air passages in the ceramic honeycomb of the catalytic converter.
    Once the passages are clogged, the converter can’t release harmful emissions from the exhaust. The other thing is that the clogged pores won’t function properly, leading to increased backpressure. All of this can cause overheating, as well as internal engine damage.
  • Failed Spark Plugs: The primary function of the spark plugs is to provide enough sparks to the engine. Once they fail in their responsibility of firing or misfiring, the spark plugs leave room for unburned fuel to make its way into the exhaust system.
    Once the unburned fuel in the converter ignites, the converter becomes pretty hot. The consequence is a complete or partial meltdown of the ceramic catalyst as a result of the excessive heat and hotness of the catalytic converter.

What Symptoms To Watch Out For

I wouldn’t want you to just blow things out of proportion by thinking you have a faulty catalytic converter without noticing the following signs below:

  • Start Problem: A faulty or clogged catalytic converter keeps exhaust gases in the engine which causes stalling from increased exhaust pressure. Some users may find this appropriate at an early stage, but once the engine begins stalling, it is suggesting a faulty catalytic converter.
  • Poor Fuel Efficiency: Should your gas mileage not be good as usual, it may indicate catalytic converter failure. The lower the oxygen that gets to the engine, the more difficult the engine will work, which results in higher fuel consumption.
  • Poor Acceleration: If you notice poor acceleration in your car, a faulty catalytic converter could be responsible. A catalytic converter reduces the general performance of your engine.
    It may also be accompanied by certain signs, including jerking and stalling when you try accelerating which is caused by insufficient fuel from getting into the engine.

What Fix To Apply

Overall, solving the problem I have discussed is simple and may require you to spend less. As opposed to what many people believe, fixing you may fix a clogged catalytic converter using DIY experience without buying a new one.

In many cases, a broken catalytic converter will cause the engine to produce rattling noise. When this happens, you may need to buy a new one for its replacement. However, you may only need to clean the catalytic converter of your 13B REW engine if it’s dirty.

2. Cracked Turbo Manifold Problem

The exhaust manifold in the 13B REW is responsible for connecting the turbochargers to the exhaust system and ensuring air goes out via the exhaust system. By design, the intake manifold is responsible for conducting the air-fuel mixture, using the pistons.

In addition, the manifold also holds the coolant and distributes it evenly to the sections that it, using the valves through the engine.

Cracked manifold is a common Mazda rotary engine problem that happens as a result of heat cycles just as you will find in other traditional engines. Heat cycles refer to heating and cooling the parts of the engine which takes place when you ignite the engine and turn it off to cool.

Metals can expand under heat and contract when cool and since the 13B rew engine is made of metal, it can easily expand.

The metal can crack due to timely contraction and expansion with connection to engine vibrations. Cracks, however, can vary in size depending on the level of exposure to heat.

Small cracks in the manifold may not impede the engine’s performance but with time, the cracks continue to expand while causing the engine to deteriorate. The formation of larger cracks will cause air to escape from the cracks, leading to pressure reduction in the engine.

The reduction of pressure causes turbochargers less effective, forcing them to work for the production of the exact power amount.

What Causes Excessive Cracked Intake Manifold

  • Excessive Heat And Pressure: One of the reasons you can have a cracked intake manifold is when it’s subject to too much heat and pressure. In other words, extreme and constant temperature change can force the manifolds to break.
  • Sustained Contraction And Expansion: The continued increase of the strain, the considerable contraction and expansion under which the manifolds work could cause them to crack.
    This is largely due to intense metal fatigue orchestrated by the cooling back and heating up of the manifolds.
  • Gasket Leaks: The problem with the exhaust manifold gaskets also significantly affects the intake manifold.
    By virtue of its position – it sits between the engine block and the manifolds- the gasket is supposed to form a seal for the petit vacuum between the manifold and engine block.
    However, when pressured due to extreme heat, the gaskets will crack and leak. When this happens, it forces the intake manifolds to crack.

What Symptoms To Watch Out For

Since we now understand what cracks in the manifold are, let’s briefly discuss some symptoms to watch out for.

  • Poor Engine Performance: The engine begins to lose power as you accelerate. It may sometimes be accompanied by the engine not taking off from a stoplight as usual. These symptoms will also require a hard pressing of the pedal to reach the next gear.
  • High Fuel Consumption: A continuous visit to the gas station may indicate a crack in the manifold. Fuel efficiency drops as the exhaust is not staying pressurized as it is supposed to be.
  • Tapping Sound: A cracked manifold will lead to creating a tapping sound around the back of the engine bay. When you observe these symptoms, it’s an indication that there is improper compression holding in the engine.
  • Coolant Leak: Naturally, a crack will create leaks in any system. From the word go, one can insinuate without being told that a crack intake manifold will cause the coolant and other fluid to leak away from their respective bays into other parts of the engine.
    Don’t forget, the intake manifold gaskets are in place to seal the coolant from leaking or escaping.
    However, if the gasket cracks or fails in its job, coolant will leak and get into the engine, causing serious mechanical issues. When this happens, you may see the engine overheating.

What Fix To Apply

Small cracks in manifold won’t get the required attention until it becomes bigger, which allow a reasonable amount of air to escape. At this point, it is best to replace the manifold. The replacement may cost a thousand dollars. It could cost less if you have DIY experience.

3. Excessive Oil Consumption

When you check the rotary engine pros and cons, you will find out that one of the concerns from users is excessive oil consumption.

Generally, rotary engines are designed with injections for the lubrication of the seals and due to this, their designs consume oil excessively.

Oil in engines serves a major purpose – lubricating parts of the engine for its effectiveness and smooth running. When your engine consumes too much oil, you’ll need to top the oil from time to time.

However, certain reasons may be responsible for the excessive consumption of oil in the Mazda Rotary 13B REW engines.

Some of the causes may include worn-out seals. If you have worn-out or damaged crankshaft seals, it may lead to high oil consumption.

This problem, however, needs quick attention to prevent further Mazda rotary engine problems. Once you begin to have a leaking valve gasket or a failing crankshaft, there will be a drop in your oil level.

What Causes Excessive Oil Consumption

By design, two things are generally responsible for the excessive oil consumption and loss in the Mazda Rotary 13B REW engine and other turbo engines. They are the design of the Mazda rew engine and the conditions under which the engine operates.

Here are the specific causes of surplus oil consumption:

  • Age: The older the Mazda Rotary gets, the weaker it becomes and the more oil it will constantly consume. Naturally, the Mazda engine doesn’t consume much fuel when it’s new or in its early 10 to 15 years. Interestingly, it is a solid, durable engine with an incredibly long life.
    However, engine inefficiency will start to set in due to old age. The gasket and seals will start to crack and break, leading to an oil leak.
  • Damaged Piston Rings: Once the pistons fail, there’s a higher chance that oil will trickle out through them and enter the internal combustion chamber.
    The consequence is dire on the engine as the escaping oil will burn and leave some clogging carbon deposits on the piston rings and the cylinder.
  • Worn Gaskets: It cannot be overemphasized that worn seals or gaskets are the main causes of oil consumption.
    Don’t forget, the gaskets are integrated into the engine and positioned between the intake manifold and the engine block to provide a seal. However, once it cracks oil, coolant, and antifreeze will start to seep out.

What Symptoms To Watch Out For

Now that we have an insight into fuel consumption in Mazda 13B engine, let’s take a look at the symptoms to watch out for.

  • Oil Leak: Oil dropping around the engine can be one of the reasons responsible for high oil consumption. In as much as you have worn-out seals without fixing, this problem may persist for a longer time. Excessive oil consumption may also be due to leaks in hoses or pipes.
  • Burning Smell: When there is a leak and touches a heated part of the engine, it melts and results in a burning smell. When you notice this, it signals a leak within your engine.

What Fix To Apply

Fixing this problem can be costly or less expensive, depending on the cause of the leak. You may, however, attempt to change the oil brand as low-quality oil tends to drain quickly. If it’s a mechanical fault, you may need the service of your mechanic to fix it.


1. Is The Mazda Rotary 13B A Reliable Engine?

Absolutely! The Mazda B13 engine is a reliable engine given its strong and durable components. However, it requires thorough maintenance and you may not get the efficiency you desire if you don’t take care of the car.

2. How Many Miles Can A Rotary Engine Cover?

On average, rotary engines can go up to 100,000 miles on average. If you’re lucky and with proper maintenance, your rotary engine can last up to the 200,000-mile mark.

3. What Are The Specifications Of The Mazda Rotary 13B REW?

Features: Specs:
Peak Horsepower (@RPM) 545 bhp @ 6,400 RPM (2008)
Torque, lb-ft 463 lb-ft @ 5,800 RPM (2008)
Valves/Springs/Retainers 24 Valves, Variable valve timing
Ignition System Coil-on-plug
Camshafts Two per head, Chain-driven
Fuel Injectors Top Feed, High Impedance, 570 cc/min (x6)

Final Thoughts

Catalytic converter and manifold are some of the most common Mazda rotary engine problems.

However, replacing these components with after-market parts will set the engine on the path to instant shutdown. After-market parts are less effective and can be dangerous to the engine.

You may, however, only choose to use them if you are sure of their effectiveness. Replacing 13B’s components is always the best choice to make as they help extend the lifespan of engines without developing problems.


Written by Kane Dan

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