Mazda RX8: Revving Near Redline Explained

Mazda's reputation today is largely built on stylish SUVs and the ever-popular MX-5 Miata. However, the Japanese manufacturer holds a significant place in automotive history for its pioneering work with rotary engines. In fact, until 2019, Mazda stood alone as the only Japanese automaker to triumph at the gruelling 24 Hours of Le Mans, and they achieved this feat with a rotary-powered machine. While the Mazda RX-7 cemented its legendary status, its successor, the Mazda RX-8, struggled to capture the same adoration, largely due to the inherent complexities and quirks of its rotary heart.

The Enduring Legacy of the Mazda RX-7

The RX-7's journey began as a successor to Mazda's earlier rotary-powered vehicles, building upon a lineage that included the Cosmo sports car. Rotary engines, often referred to by enthusiasts as 'spinning Doritos' due to the shape of their rotor, offer distinct advantages over traditional piston engines. They are generally lighter, smoother in operation, and possess a simpler mechanical design. Crucially, they can produce more power relative to their displacement, allowing for more compact engine packaging. This translated into the first-generation 'FB' RX-7 (1978-1985) boasting a low centre of gravity and an almost perfect 50:50 weight distribution, characteristics that were carried forward and refined in the second-generation 'FC' (1985-1992) and the highly acclaimed third-generation 'FD' (1993-2002).

The FC RX-7 was a significant step forward, featuring a 1.3-litre turbocharged 13B rotary engine that produced 189 horsepower. The 'Turbo II' variant further enhanced performance with an updated turbocharger and an air-to-air intercooler, pushing output to 200 horsepower. Its prowess was recognised when it was named MotorTrend's Import Car of the Year in 1986, with the Turbo II also earning a coveted spot on Car and Driver's 10Best list. However, it is the FD RX-7 that many consider the pinnacle of the RX-7 lineage. Hagerty reports that the FD's 1.3-litre 13B rotary was equipped with twin sequential turbochargers. A smaller turbo spooled rapidly to provide immediate low-RPM torque, while a larger turbo kicked in at higher revs to maximise power, resulting in a total output of 252 horsepower. Furthermore, as noted by users on the r/cars subreddit, the FD emerged during Japan's 'Bubble Era,' a period of economic prosperity that allowed for robust engineering. This meant the 13B engine was often over-engineered and highly receptive to tuning for increased power. Its appearances in popular culture, such as the anime 'Initial D' and the 'Fast and Furious' film franchise, further cemented its desirability and led to many being modified.

The RX-8: A Promising Successor with Caveats

Building on the RX-7's success, Mazda introduced the RX-8 in 2003, continuing its commitment to rotary power. Despite featuring a naturally aspirated 1.3-litre rotary engine, dubbed 'Renesis,' producing a respectable 232 horsepower, the RX-8 never quite matched the legendary status of its predecessor. Mazda's decision to cease production of rotary engines after 2019 further highlighted the challenges faced by this unique technology.

Understanding the RX-8's Renesis Engine Issues

The primary challenges with the RX-8's Renesis engine stemmed from differences compared to the RX-7's 13B. Reports from Jalopnik suggest that the Renesis engine's housing was not as robust and could be prone to warping over time. Additionally, Mazda had to make modifications to the exhaust system to meet increasingly stringent emissions regulations, which may have impacted performance. However, the most critical issue revolved around the apex seals. As explained by Popular Mechanics, rotary engines utilise a triangular rotor that spins within a housing, creating three distinct chambers for intake, combustion, and exhaust. Engineering Explained's Jason Fenske elaborates that the integrity of the apex seals is paramount, not only for separating these chambers but also because one side of the rotor is consistently hotter than the other. This inherent thermal gradient places significant stress on the apex seals, constantly trying to warp them. Unfortunately, the apex seals in the Mazda RX-8 were designed to be lighter and thinner than those in the RX-7, making them more susceptible to premature wear and failure. The extent of these issues led to 2004-2008 Mazda RX-8s experiencing numerous engine-related problems, prompting Mazda to extend warranties and reimburse owners for repairs, as noted by Autoblog.

The RX-7's Own Set of Challenges

It's important to acknowledge that the FD Mazda RX-7's 13B rotary was not without its own vulnerabilities. Like all rotary engines, the 13B was noticeably less fuel-efficient than comparable piston engines. Hagerty also reports that improper treatment could lead to apex seal failure. The sequential-turbo setup on the FD also presented its own set of complications. The intense heat generated by the twin-turbocharged 13B could, in some instances, cause the catalytic converter to overheat and even melt, as reported by The Straight Pipes. A built-in warning light was even incorporated to alert drivers to excessive exhaust temperatures. This extreme heat not only could make the cabin uncomfortably warm but also had the potential to degrade vital engine components. High temperatures could cause vacuum hoses, radiator hoses, and wiring harnesses to become brittle, leading to performance degradation, fluid leaks, and electrical issues. Furthermore, the RX-7, much like the RX-8, was susceptible to problems arising from owners who were not fully aware of its unique maintenance requirements.

Essential Rotary Engine Maintenance

With careful and correct maintenance, both the Mazda RX-7 and RX-8 can be remarkably reliable vehicles. Jean-Pierre Derdeyn, from rotary specialist shop Derwin Performance, informed Hagerty that rotary engines, when properly cared for, can achieve well over 150,000 miles without significant issues. One crucial aspect of rotary care is to avoid shutting down the engine when it's still cold. This practice, known as 'cold-flooding,' can thin the oil on the rotor housing walls, leading to excessive wear on the seals. Conversely, revving a Mazda RX-8 near its redline can actually be beneficial. Owners on RX-8 forums report that this helps to burn off excess carbon buildup within the engine. This carbon accumulation, if left unchecked, can lead to internal engine damage and corrosion.

Perhaps the most significant difference between rotary and piston engines lies in oil consumption. Rotary engines naturally consume oil as part of their combustion process, a characteristic that standard synthetic oils are not ideally formulated to handle. Derdeyn recommends using a conventional oil with a high zinc content. Some owners even opt to modify their vehicles to accept two-stroke oil, a practice commonly seen in racing applications. In terms of oil changes, instead of the typical 7,500-mile interval for piston engines, it is preferable to change the oil in a rotary every 3,000 to 5,000 miles.

Addressing the RX-8's Perceived Drawbacks

Despite the reported issues, a properly maintained Mazda RX-8 offers compelling advantages over the RX-7, particularly in terms of affordability. While top-condition stock Mazda RX-7s can command prices up to $34,500 according to Hagerty, an RX-8 is significantly more accessible. One example recently sold on Bring a Trailer for a mere $10,750, and this was for the more performance-oriented R3 model. Furthermore, unlike the RX-7, the RX-8 is a genuine four-seat sports car, capable of comfortably accommodating four adults on longer journeys, as highlighted by Car Throttle. Its handling dynamics are also considered by many to be even more refined than those of the FD RX-7.

For those considering an RX-8, Grassroots Motorsports suggests opting for a 2009 model or later. Mazda implemented improvements to the Renesis engine's fueling and oil metering systems in these later models and equipped them with a more robust six-speed manual transmission. The only other notable weakness commonly cited is the somewhat fragile OEM ignition coil system, though this is a relatively straightforward fix with readily available aftermarket components. For instance, Black Halo Racing offers an upgraded system that even comes with a warranty.

The Verdict: Is the RX-8 Worth Considering?

While the Mazda RX-7 rightfully holds its place as an admired automotive icon, the RX-8, despite its challenges, does not deserve the widespread criticism it sometimes receives. Its unique rotary engine, combined with its practical usability and engaging driving dynamics, makes it a compelling proposition for enthusiasts looking for something a little different. Understanding and adhering to its specific maintenance needs is key to unlocking its potential and enjoying its distinctive character. So, to answer the question: revving your Mazda RX-8 near redline, in moderation, is generally considered beneficial for clearing carbon deposits. However, as with any high-performance engine, responsible driving and diligent maintenance are paramount to ensuring longevity and enjoyment.

Frequently Asked Questions

Q1: Is it true that revving a Mazda RX-8 near redline is good for it?
Yes, it is generally considered beneficial for rotary engines like the one in the RX-8 to occasionally rev near redline. This helps to burn off carbon deposits that can accumulate in the combustion chambers and exhaust ports, which can otherwise lead to engine issues.

Q2: What type of oil should I use in a Mazda RX-8?
Rotary engines consume oil as part of their combustion process. It's recommended to use a conventional oil with a high zinc content. Some owners also use specific rotary-blended oils or even modify their cars to accept two-stroke oil. Avoid standard synthetic oils not formulated for oil-consuming engines.

Q3: How often should I change the oil in my Mazda RX-8?
Due to the oil consumption and the nature of rotary engines, it's advisable to change the oil more frequently than in a typical piston engine, ideally every 3,000 to 5,000 miles.

Q4: What are the main differences between the RX-7 and RX-8 engines?
The RX-7's 13B rotary engine was twin-turbocharged and generally considered more robust, though it had its own issues like heat management. The RX-8's Renesis engine was naturally aspirated, designed for better emissions and smoother power delivery, but its apex seals and housing were considered less durable than the RX-7's.

Q5: Are Mazda RX-8s reliable if properly maintained?
Yes, when maintained correctly, Mazda RX-8s can be reliable. Key to their longevity is regular oil changes, using the correct oil, avoiding cold-shut downs, and occasionally revving the engine to clear carbon buildup. Addressing common issues like ignition coils with aftermarket parts also significantly improves reliability.