Until 1995, Mazda built the popular Rx-7 with a 13B-REW engine (and until 2002 in Japan). Mazda finally released the eagerly awaited Rx-8 in 2012, nine years after it was first announced. While the Rx-7 was lauded for its ability to be tuned, the Rx-8 was disappointingly underwhelming in terms of raw power.
The 13B Renesis, also known as the 13B-MSP (multi-side-port) rotary engine, powers the Mazda Rx-8. There were no twin turbochargers in the 13B-predecessors, REW’s so it had a naturally aspirated 1.3L engine. With 238 hp and 159 lb-ft of torque, it was 42 hp and 72 lb-ft less powerful than the 13B REW, which had the highest output.
The 13B engine in the Rx-8 had a difficult-to-tune ECU in addition to its lower horsepower numbers. When you add the lack of forced induction to the mix, it’s no wonder enthusiasts weren’t thrilled with the 13B’s performance.
Despite its lackluster performance, the Rx-8 was a joy to drive thanks to its lightweight design and superior suspension and handling. The Rx-8 was a great platform despite its power limitations, winning the 2003 international engine of the year award, the 2004 best sports car award, and the Car and Driver’s Ten Best list from 2004-2006. The 2010 Best-Handling Cars Under $100,000 list ranked it third overall, demonstrating the car’s value as a thrill-seeking sports car.
Mazda Rx-8 13B Engine Problems
The 13B Renesis engine in the Rx-8 is not known for its sturdiness. The 13B engine had a slew of issues, and it frequently needed a rebuild before it reached the 100,000-mile mark. The following are the most frequently encountered issues with the Rx-8’s engine:
- Leaking Apex Seals
- Ignition Coil Failure
- Engine Flooding
- Catalytic Converter Failure
- Starter Failure
Other Noteworthy 13B Rx-8 Problems
- Excessive Oil consumption
- Clutch Master & Slave Cylinder Failure
1. 13B Leaking Apex Seals
The 13B RX-8 engine’s most vulnerable component is the apex seal. Two rounded triangle-shaped rotors make up the 13B rotary engine. These rotors rotate inside an oval-shaped rotor housing. Rotor contact is limited to the triangle’s three points, which are encased in plastic. These are known as the apex points, and an apex seal is located at each one to keep compression contained within the combustion chamber.
The seals are pushed against the rotor housing by a spring. Because the housing and seals are both metal, oil is used to keep them from corroding.
Why Apex Seals Go Bad
Apex seals can fail for a variety of reasons. To begin, all three phases of a rotary engine’s operation circulate within the same housing. Thus, the apex seals are constantly exposed to temperature fluctuations. As the temperature changes, the seals may become brittle and begin to crack.
To begin with, the pre-ignition can create enough back pressure on the seals to force them from the rotor and onto the housing. After that, the seal devours the rotor housing like a ravenous animal.
Small compression leaks can occur as well as a result of the spring force weakening over time. High friction between the brake rotors and housing caused by low engine oil can cause severe damage to both.
It’s a fact of life that metal on metal will eventually fail. Seals wear out more quickly in an engine spinning at 9,000 rpms than they would on a lower revving engine. Because the 13B has two rotors, there are a total of six apex seals, increasing the likelihood of a leak.
Symptoms of 13B Apex Seal Failure
- Loss of compression
- Significant power losses
- Hard starts or no starts
- Engine stalling while running
- Constant misfires
The rotor housing loses compression when the seals start leaking or fail completely. Due to the fact that compression is a key component of combustion, any loss in compression results in a significant drop in performance.
Total seal failures are common on the Rx-8. Small leaks, on the other hand, are almost certain on any 13B with a long service life. By the 100,000-mile mark, the seals are usually corroded and in need of replacement. If the rotor seals come loose and fall into the housing, the metal on the rotor and housing will be completely eaten away, necessitating an engine replacement over a rebuild.
Apex Seal Replacement Options
The 13B engine’s apex seals usually send it to the graveyard. When the seal breaks, one of two things happens:
- For leaking seals, you have two options: rebuilding the engine or getting new seals. Despite the fact that it appears to be the simplest option, pulling and completely disassembling the engine makes this a costly and time-consuming task.
- For this reason, when the seals come out of the rotor, they must be removed from the housing or else the rotor will chew through it and destroy the metal, requiring new housing. While you can fix the problem by replacing the housings and rotors, the cost forces most people to buy a new car and toss the old one.
When it comes to apex seals, aftermarket options claim to be more reliable than OEM ones.
2. RX-8 Ignition Coil Failure
Even though it’s not the most serious issue, the Rx-8 is known to go through ignition coils like candy. The coil-near-plug ignition system in the Rx-8 connects the ignition coils to the spark plugs via spark plug wires and is used in vehicles like the Rx-8. During combustion, the spark plugs require a lot of electricity, which the ignition coils provide by converting battery power into high-voltage electrical currents.
Piston engines use ignition coils that fire every other revolution of the engine. Every revolution of a rotary engine fires a rotor. There are a lot more ignition coils firing on a 9,000rpm engine because of the higher redline speed.
Electrical components such as ignition coils naturally degrade over time. Wear and tear reduces the converter’s capacity, and as a result, spark plugs lose their ability to ignite.
The Rx-8’s ignition coils usually need to be replaced after 30,000 miles. For safety reasons, it is always best to replace ignition coil and spark plug wiring when performing an ignition coil replacement. Fortunately, OEM replacements aren’t prohibitively expensive these days, and swapping them out is a simple do-it-yourself project.
RX8 Bad Ignition Coil Symptoms
- Rough idling
- Hard starting
- Poor acceleration
- Check engine light
3. 13B RX-8 Engine Flooding
It’s not a good idea to take your Rx8 through a flooded area. Engine flooding, on the other hand, has nothing to do with water entering the engine from the outside.
In terms of air pollution, the RX8 is a poor choice. Emissions were the real reason for the vehicle’s discontinuation from the UK market in 2010. Warm engines emit fewer pollutants than cold engines. As a result, various cold start cycles are offered by various manufacturers in an effort to warm the engine as quickly as possible.
As part of the cold start cycle, the 13B Rx-8 injectors dump a large amount of fuel into the combustion chamber while also pumping more air through the system to help burn the exhaust gases even more and heat the catalytic converter more quickly.
A flooded engine can occur if a Rx8 is turned off too early during the cold start cycle. Spark plugs can’t ignite the fuel, so the engine won’t start because of a buildup of gasoline inside the combustion chamber.
RX8 Flooding Symptoms
- The vehicle’s engine won’t start.
- When attempting to start the engine, I could smell gasoline.
- An engine’s whining while it tries and fails to start
In short, your car won’t start. Even though flooding your engine can damage your spark plugs, it’s not going to be a big deal.
How to Prevent 13B Engine Flooding
Stopping the engine before it has finished its cold start cycle causes flooding. Before turning off your 13B rotary engine, make sure it’s nice and warm. Let it warm up first so that the extra fuel being poured into the combustion chamber can be used up before the engine is shut off.
Moving your car to the driveway without first turning it off is a big no-no. To burn the fuel, let the car idle for a few minutes before turning it off. Then, quickly rev the engine to 3,000 rpms several times to get it going again. However, when the engine is cold, don’t over-rev it.
How to Unflood an RX8 Engine
The fuel injectors are disabled when the 13B engine is run with the throttle all the way open. Unflooding the engine is as simple as cranking it while the accelerator pedal is depressed all the way. Put the car in park or neutral before you begin.
While pressing the accelerator pedal all the way down, turn the engine on for up to 20 seconds. If that doesn’t work, try cranking the engine for another 20 seconds without pressing the accelerator pedal. Keep doing this until the engine starts working again, then repeat the process. Restart the process after waiting 5 minutes to give the starter a chance to cool down.
4. RX-8 Catalytic Converter Failure
On the majority of modern automobiles, the most critical emission control system is the catalytic converter. Palladium and platinum are used to make the interior of a “cat,” as it is commonly referred to.
The metals are arranged in a honeycomb structure, and chemical reactions help to reduce emissions. By reacting with the catalytic converter’s metals, harmful exhaust gases are converted to less harmful ones like carbon dioxide.
Catalytic converter failure in an RX8 is most commonly caused by faulty spark plugs, spark plug wires, or ignition coils.
When the catalytic converter heats up to 500 degrees or higher, it becomes extremely dangerous to operate the vehicle. The spark plug will not light if any of these three ignition components are damaged, resulting in a buildup of fuel in the combustion chamber. Afterward, the extra fuel is discharged into the exhaust system, where it can ignite the honeycomb structure of the catalytic converter.
Melted metals in the catalytic converter clog the exhaust system, resulting in a significant amount of back pressure. When the engine is under this much back pressure, it has a hard time making power and turning.
As a result, struggling to rev the engine past a certain level is the most common sign of a bad cat in a Rx8. Usually, it won’t go beyond, say, 8,000 rpms before rapidly degrading until it won’t go beyond 4,000.
Bad Catalytic Converter Symptoms – 13B Engine
- Engine will not rev past a certain level and becomes stuck in the rev range
- There has been a large drop in power.
- Engine light on and sluggish performance
Preventing and Replacing Failed Catalytic Converters
Cat failure can be caused by faulty plugs, wires, or coils, as previously stated. To avoid this problem, replace these parts as soon as you notice that they are beginning to go bad. Long-term use of a faulty catalytic converter can result in engine damage due to the hot exhaust gases being returned to the combustion chamber.
To fix a bad cat, replace your ignition system first, and then your cat. Replacement with an OEM cat is an option, but these can be expensive, so it isn’t always recommended. The second option is to buy a catless or catted midpipe from a third party aftermarket supplier.
Catless midpipes are less expensive than catted ones, but they are also illegal. Alternatively, you can slit open the cat and remove all of the metal from the inside, effectively transforming it into a catless midpipe, which is also against the law.
5. Mazda Rx8 Starter Failure
For starting an engine, a starter uses an electric motor that draws power from a battery. Combustion is impossible without rotating rotors. Starting the engine requires moving these components, and the starter is responsible for doing just that.
In cold weather, the RX-8’s starter performs appallingly. In colder weather, the ignition system also performs poorly, requiring the already-weak starter to crank the engine for longer before it will start.
Mazda merely utilized a subpar starter motor in these models to save money. Older cars are still susceptible to this problem, even after a recall in 2006 and a change in the motors. However, this is less common than in 2004-2006 models. A failed starter motor is the result of a bad starter and an ineffective ignition system.
Starter Motor Failure Symptoms
- Hard starts
- No starts
- Engine won’t crank at all
- Grinding noise during crank
- Starter engages but won’t crank
If you hear a clicking sound, the battery, not the starter, is malfunctioning. If your starter is defective, your only option is to have it replaced.
Other RX8 Problems
It takes a lot of work to keep the RX8 running smoothly. Taking good care of it is critical if you want it to last a long time. While the major issues with the 13B engine have already been mentioned, there are a few others that should be mentioned as well.
RX8 Oil Consumption
Contrary to popular belief, excessive consumption of engine oil on the 13B is not a bad thing. When oiling the apex seals, it’s necessary to rotate the engine so that oil burns naturally.
Increased oil consumption is possible if you have a problem with leaking apex seals, but adding 1 quart of oil every 1,000-1,500 miles is not unusual. Low oil levels can cause apex seal failure, and as a rotary owner, you must be fully aware of this. Don’t forget to keep oil in your trunk when you go out of town.
Clutch Master & Slave Cylinder
Manual RX8 clutches are notoriously unreliable for some reason. Both the slave and master cylinders are prone to failure. These parts failed on me twice in five years and 50,000 miles of driving. It’s easy to tell if a clutch is too soft or too easy to push in. Getting the clutch to engage is a major pain and results in a lot of gear grinding.
Manual Transmission Synchros
In manual transmissions, the speed shaft is adjusted by gear synchronizers before the engine reengages the transmission, synchronizing the collar and gear speeds. Manual Rx8 synchros frequently fail, resulting in gear grinding.
If you overshift or pull/push the shift knob, you run the risk of damaging your synchro. The synchro saver, which prevents you from shifting too far into gear, is a great $75 investment.
Make sure the oil is always at a sufficient level. Every 1,000-1,500 miles, top off the oil with a quart from your trunk. Oil should be changed at least once every 5,000 miles. Avoid allowing the engine to overheat or running out of oil.
My personal favorite: if you hit the redline once a day, you’ll stay away from the mechanic.
Redlining these engines actually benefits them because it removes carbon buildup.
Mazda RX-8 13B Renesis Reliability
The Rx-8’s 13B-MSP engine, on the other hand, has a history of failures. However, poor maintenance and owners who do not understand the requirements of rotary engines are the primary causes of reliability issues.
As a result, by the time they reach 100,000 miles, most of these engines will be suffering from compression loss or have completely lost compression.
80,000-mile engine failures are also common if the engine was not properly cared for during that time period. The engine on a well-cared-for 13B may last only 125,000 miles before needing a rebuild.
The 13B rotary Rx8 is prone to a number of other failures as well, including total failure. Despite being less expensive to replace than catalytic converters or ignition coils, starters, ignition coils, spark plugs, and clutch cylinders frequently fail.
There were a few other issues that came up during my time with the RX-8, such as broken door locks ($1,100 fix), waterlogged headlights, grinding synchros, and sway bar end link failure.
The RX8 is a blast to own and drive, but in today’s world, it’s unlikely you’ll come across one that’s still in good shape after a recent rebuild. To summarize, these cars can be had for half the price of a 1990s Miata and have twice the mileage.
What are your thoughts on the RX8?