If there ever was a persistent complaint about the RX8, it’s that the RENESIS engine powering it is lacklustre. It’s the same problem that many Japanese sports car face, the powertrain doesn’t invigorate the driver.
That includes cars such as the MX-5, GT86 and most other Japanese-built sports cars. Japanese philosophy to building a sports car emphasizes driving purity. This means that the power figure tends to take a back seat most of the time. Hence, you’ll notice that many modern-day Lexus sports cars are still naturally-aspirated, and even the new NSX balances power with control.
However, because of that, Japanese sports cars don’t perform as well in sales when compared to their peers. People like the feel of a neck-snapping supercharged American V8 that the Hellcat offers (Also swapped in to Miata’s). In Europe, people put 700 horsepower into a station wagon. Even the once shockingly rapid GTR is getting a bit long in the tooth.
But these Japanese sports cars have a tendency of being popular modified cars. The classic Japanese sports car more so. So if you own an RX8, thinking it’s a bit down on power, you’re in luck. There’s room for upgrades to improve the power output of the RENESIS.
Turbocharging The RX8
People exclaimed their disappointment in the RENESIS. Overlooking its reliability woes for a second, it just didn’t make enough power. The proposal to market the RX8 as more attainable and driver-friendly, along with stringent emissions regulations limited the RENESIS.
It’s often compared to the engine it’s supposed to replace – the 13B-REW. The sequential twin-turbocharged rotary engine that powered the RX7. The turbochargers may have compromised emissions while increasing weight and complexity, but they were effective.
In fact, found in the most extreme state of tune, the 13B-REW could produce 276 horsepower and 314 Nm of torque. That’s compared to the RENESIS which makes 232 horsepower and 216 Nm of torque maximum. So the disappointment in rotary fans wasn’t unfounded.
However, it’s not the power that’s the culprit. In fact, it’s mighty impressive that Mazda managed to extract this much power from the RENESIS. It’s the torque and the quality of torque delivery. With the sequential turbocharging of the 13B-REW, the RX7 never felt ’empty’, even when stock.
Forced induction mitigates the rotary engine’s inherent lack of torque. Hence, soon after the RENESIS’s debut, many tuners went to work attempting to extract more power from the RENESIS. Of course, turbocharging the RENESIS is a difficult task.
For one, it’s developed from the factory without forced induction in mind. The RENESIS was never meant to be turbocharged, so all modifications Mazda made to it was to extract power naturally. So any turbo kit had to be developed from scratch to fit the engine compartment and not blow the RENESIS up.
Thankfully, experimentation and development period overtime meant that it’s possible to turbocharger the RENESIS. Tuners found mostly positive results at turbocharging the RENESIS. It’s by no means easy, and it will probably be more money than you expect. But, if you want a turbocharged RX8, this might be the way to go for you.
RX8 turbo kits
Do take note that this only serves as a guideline. There are no turbo kits that are easy and bolts in directly. The RENESIS is a difficult engine to turbocharge, so perform your due diligence at researching prior to actually purchasing a kit.
Prepare to set aside $10,000 for the whole ordeal. Properly made turbo kits are expensive, and you need supporting mods to avert catastrophic engine failure. Also, before you even attempt to mod your RX8, make sure the engine is healthy. The only way to know is through a proper rotary engine compression test. Turbocharging a near-dead RENESIS will only end expensively.
RX8Performance Turbo Kit ($6,395)
Perhaps one of the most popular RX8 turbo kits around. After all, where better to buy a major modification kit from than people who specialise in your exact model? Based in Florida, RX8Performance started with an RX8 it bought and developed parts from there.
It’s also a popular turbo kit amongst RX8 enthusiasts. If you’re targeting for a responsive engine with a bit more power, then this kit is for you. It’s developed from the ground up to be the kind of turbocharged RX8 Mazda might build.
The kit is developed with drivability in mind. This means that the RENESIS’s approachability must be maintained. A well-behaved turbocharged RENESIS that delivers punchy torque yet sustain track abuse. And for such a kit to be successful, actual owners’ feedbacks have been taken into account.
This is a low-mount kit, meaning that the turbo is tucked away neatly, around where the RENESIS’s stock extractor is. A low-mount design keeps the heat to the hot-side. That’s in contrast to top-mount kits, which increases under-hood temperature and can cook fragile plastic parts.
With a low-mount kit, reliability is improved, but space is at an absolute premium. All of the turbocharger exhaust design is kept low and centred to maintain the chassis balance. Even with a turbocharger, the original Mazda intake management and oil metering are kept intact. No serious chassis alterations are necessary too.
RX8Performance has also taken advantage of the RENESIS’s unique exhaust flow characteristics. The exhaust manifold is designed to take advantage of the centre housing exhaust port which has a high gas velocity to improve spool response.
A Synapse diverter valve is utilised to recirculate charged air back into the turbo air inlet. This helps to avert the sudden pressure spike when you shut the throttle valve. Hence, it can improve turbocharger response at part-throttle. Albeit it’s not a significant impact.
The main beating heart, and most of the money, is spent on the turbocharger itself. It’s a dual ceramic ball bearing Precision Turbo CEA 6266 with a billet compressor wheel. It’s very much a time-proven turbocharger. While it’s capable of providing up to 700 horsepower worth of airflow, when adopted for low-boost use it can be markedly responsive.
The exhaust side is .82 A/R with a V-band clamp design. Boost is managed by a 46mm Precision Turbo wastegate that by default discharges into the 3″ downpipe. A direct atmospheric wastegate vent is optional.
With this kit, the stock battery location, factory hoses and pulleys are maintained. The stock MAF sensor is used thanks to the implementation of proper air straighteners. This reduces the headache when it’s time to tune your turbocharged RX8.
It’s a big kit, therefore many parts are optional. It all depends on your goal. The intended power level from RX8Performance is approximately 350 RWHP, but with such a versatile system you can push way further. However, caution is advised as you can most definitely blow your RENESIS up when you make too much power.
GReddy RX8 Street Turbo Kit (US $5,300)
This is an old discontinued kit, so availability is getting dubious. However, if you can source one, it’s one of the more affordable kits you can find. If your intent is a mildly boosted RX8 with enough poke to inspire you, then the GReddy kit might just be what you need. UK Buyers look here.
GReddy is a Japanese tuning legend, so explanations of the brand’s worthiness aren’t necessary. Similar to the RX8Performance kit, it’s a low-mount kit that features a very modest GReddy T618Z turbocharger. Which is, by all means, a ‘soft’, near-OEM application turbo only.
This means that you can expect about 270 WHP running the GReddy kit. You may be able to squeeze a bit more, but the turbo will be straining by ~0.8 bar of boost. What it has going for it is instantaneous boost response. It covers for the RENESIS’s lack of low-end torque while providing an appreciable bump in power in the upper rev range.
It’ll turn the RX8 into a relatively brisk car without compromising handling characteristics. Intriguingly, the kit also includes GReddy’s own pre-programmed E-Manage that supposedly offsets the need for a tune. However, it’s a piggyback system that’s flawed at compensating for such a major modification. A standalone management system is recommended as an upgrade if possible.
Out of the box, the turbo is designed to run at only 5 psi of boost from its internal wastegate actuator. This is good for achieving GReddy’s projected power gains with a mild headroom for improvements. It’s plenty for those intending to run a daily RX8 though.
However, there are flaws with this kit. It mainly lies in the turbocharger itself. Being a rather archaic turbocharger design, it’s only oil-cooled. This is good at lowering costs and to prevent raising the coolant temperature of an engine that already runs hot.
This paired with the high heat retention cast iron exhaust manifold means that the oil within the bearing housing cooks easily. Turbocharger reliability is thus compromised. However, you can always opt for an improve turbocharger, or even purchase a kit upgrade from MazdaManic or BNR Supercars.
The good thing about this kit is that many have installed it before, and thus, information is readily available. You should definitely take a read through here and here to better understand the kit. Here’s a build thread using the GReddy kit with improvements.
Of course, the cons with the GReddy kit is plain to see. It’s intended to be a straightforward kit to improve output by just a bit. This means that there’s not much versatility for power levels unless you intend to upgrade. There’s also no blow-off valve or boost gauge included, but the E-Manage provides some monitoring of the ECU data.
SFR RX8 Turbo Kit ($6,395)
Speed Force Racing (SFR) is a California based performance provider specialising in fabrication. Forced induction kits are their forte, and they’ve built cars from mildly boosted to serious 2000 horsepower monsters before.
Their RX8 turbo kit is intended for those who want a serious turbocharger kick. It’s a top-mount turbo kit very different from the aforementioned kits. The disadvantages is clear, more heat is introduced underneath the bonnet. This is detrimental to the durability of the plastic bits. Furthermore, the turbine is located close to the oil metering pump, which can be problematic without a workaround.
However, being a top-mount kit means SFR has a lot more engine bay real estate to work with. It also makes charge pipe routing more straightforward. The RX8 has a lot more space in front of the RENESIS, meaning that an adequately sized Turbonetics T60-1 turbocharger can be used.
It’s a ceramic ball-bearing turbo developed to improve upon the renowned Garrett T3/T4 design. Turbonetics has balanced the turbocharger for dimensions, response and output. While it’s capable of flowing enough to produce 600 horsepower, in this kit it’ll push the RX8 to a rated 330 WHP at ~0.6 to 0.7 bar of boost.
That said, someone has been documented to make ~370 WHP using this kit. You’re getting almost everything you need in the kit too, along with a 46mm Tial wastegate and 50mm Tial dump valve. Note that the battery has to be relocated for the kit though. Heat wrap is also included in the kit to reduce the engine bay temperature.
If you decide to go for this kit, it’s definitely necessary that you upgrade your RENESIS’s cooling system, ignition system and fueling system prior to handle it. Turbocharging supporting mods such as aftermarket engine management and boost monitoring is mandatory as well.
Of course, being a fabrication specialist, SFR offers the entire kit to be customisable. You’ll have to get in contact before you make your order and they’ll set you up with a kit appropriate for your goals. Everything in the kit is also nicely polished, which gives a show-car look when you open your bonnet.
If you have a bigger budget, don’t mind having to source accessories and multiple additional parts to get it running, then the SFR kit is generally well-received. Here’s a build thread using the SFR kit with good results.
These are kits that are either not popular enough to garner sufficient opinion, or controversial in reviews. They might not necessarily be bad, but you should pay extra caution if you decide to go with these kits. After all, turbo kits are just an assortment of parts that you can still fabricate or source yourself.
Turblown Engineering RX8 Turbo Kit ($6,164)
If you’re interested in making serious power with your RX8, then the Turblown kit is designed exactly for that. This is a top-mount kit for those aspiring to make 400+ WHP, and don’t mind making the sacrifices for it.
You’re flexible on which turbocharger you use, but the Turblown recommends using the Borg Warner EFR 8374 IWG turbo. It’s the BorgWarner internal wastegate alternative to the Garrett GTX3582R. When paired with E85 and at approximately 1.2 bar of boost, you can expect to make around 400 WHP already. Power increases exponentially with boost.
The great thing with this turbocharger is its internal wastegate design. This simplifies things considerably, as you don’t have an external wastegate to make room for, and no extra exhaust routing is required. Admittedly, it’s a compromise between simplicity and total flow volume, but the IWG turbo is plenty adequate in most applications.
For the S1 RX8s, the stock oil metering pump has to be deleted. This means that you need to premix 2-stroke oil at every fuel stop. The necessary modifications involved are included in the kit. You also need to relocate the battery and decide upon an aftermarket management system on your own.
While Turblown seems to be quite reputable, initially their reputation in the RX8 forums are questionable at best. There are definitely dyno graphs to validate their claim, but the reliability of the RENESIS afterwards is dubious. Its workmanship was also once controversial, to say the least.
However, since then, things have seemingly improved. Some remain doubtful of Turblown’s reliability as a kit builder, but there are people vouching for its kit quality. When you check its Facebook page out, ti seems like it puts out some pretty nice work indeed.
Therefore, it’s up to you to judge whether if Turblown is trustworthy enough. It also produces an RX8 low-mount turbo kit for those that want a milder setup. The target power output with the low-mount kit is around 330 WHP, so it depends on your goal. Once you have fitted your turbo dont forget to check out different body kit options.
Mazfix Stage 1 RX8 Turbo Kit ($10,500 Fitted AU)
If you want an all-encompassing kit, then Mazfix might be your best bet. However, the catch is that it’s based in Australia and only offers the kit in a drive-in basis. However, for the decidedly high-price, it provides a one-stop solution. You drive your RX8 in, they sort your car out in due time, and you drive your turbocharged RX8 out.
The stage 1 kit promises approximately 300 horsepower at the wheels. And given that Mazfix is a reputable performance shop familiar with rotary engines, I’d trust them to deliver a quality product. There’s not much you can change about the kit though.
Of course, to preserve the reliability of the RENESIS, the power output is generally limited to around 280 WHP. Little room for flexibility as a stage 1 drive-in kit. Being rotary engine specialists mean that they have plenty of upgrades available for your target. You just have to communicate with them prior.
You can see here for thoughts on driving a Mazfix powered RX8.
Should You Turbocharger Your RX8?
So, after considering your options, should you get a turbocharger kit for your RX8 at all? The RENESIS is difficult to be turbocharged and remain reliable. In fact, some states that a RENESIS would only last 30,000 miles being turbocharged.
However, the reliability of a turbocharger kit still comes down to proper installation and tuning. Both are equally critical. The amount of money and effort you’d have to spend increases exponentially with the amount of power you intend to make. You might want consider a complete engine swap or look specifically at an LS swap instead.
For the RENESIS, over 350 WHP on pump gas is considered serious power. Reliability and fuel consumption aren’t expected to be excellent here. With E85, you may be able to push 450 WHP out of an unopened RENESIS. But you’ll be pushing the limits of the RENESIS.
As the saying goes, modifications made are always a compromise between budget, reliability and high power. To turbocharge any naturally aspirated car, you’d have to make the supporting mods to stop your engine from blowing up.
With fueling mods, cooling system upgrades, proper aftermarket engine management, realistic targets and safety nets, even a turbocharged RENESIS can be robust. Of course, you should do ample research beforehand and read up on any turbo kits you intend to install.
If you just want a bit more power to spice up your RX8 driving experience, then the GReddy kit is just perfect. It’s very well documented about, and the results are proven by many. It’s such a staple turbo kit for the RX8 that people sell upgrade kits to fix the flaws in the kit.
There’s also the problem with the E-Manage piggyback system offered in the kit though. While it’s a pre-tuned to fit the application, it’s simply not ideal for a major engine modification. It’s recommended that you replace the E-Manage with a standalone management system.
If you have a bit more money to spare and a loftier target, then the RX8Performance Turbo Kit is a worthwhile consideration. It’s a known, quality turbo kit that offers ample headroom for power upgrades in the future.
A low-mount kit is generally considered to be milder and appropriate for performance street applications. But if you want the wow-factor when you open your bonnet, then the SFR Turbo Kit might be your best bet.
RX8 Turbo Kit Verdict
If you yearn for the feel of a turbocharged rotary, then there’s also the option of swapping in a 13B-REW. But it won’t be any easier of a job than turbocharging the RENESIS.
Got the time and resources? Then you might be better off assembling your own turbocharger kit. You’ll need to be handy with fabricating, but it should free up more of your budget for the additional mods you’ll have to make.
There are also multiple other ways for you to seriously improve the power output of your RENESIS. People have experimented with supercharging, nitrous and porting the RENESIS. Others just swap in a nicely rebuilt R3 engine. Therefore, you should consider your options before going with turbocharging.