The Definitive Guide to Mazda RX-8 Performance Mods. The Mazda RX-8 can be a lot of fun to own and operate despite its engine issues. It is a fun street or track car for any car enthusiast because what it lacks in engine, it makes up for in handling and quickness. Used Rx8s are inexpensive, making them a desirable performance vehicle for any income. However, even though 100k kilometers may not seem like much for most vehicles, it is a lot for the 13B rotary engine in the RX-8.
The finest performance modifications for the Mazda RX8 will all be covered in this guide. A few additional horsepower goes a long way on these engines at just 3,000 pounds. But before we get started with the modifications, it is important to note that the Rx8 is an expensive vehicle to alter and that the power increases are only moderate without adding a turbocharger or porting the engine.
Additionally, the 6-port 13B engines that were fitted to RX8s with manual transmissions will be the main emphasis of this guide. The 4-port motor used in automatic transmission vehicles has less power out of the box and is therefore less suited for tuning. Get a manual instead of an automatic if you want your RX8 to have reliable propulsion. On the 4-port engines, the expense does not outweigh the power gains.
Mazda RX-8 Maximum Strength
In the US, a standard RX-8 13B rotary engine generates 232 horsepower and 159 lb-ft of torque. A little less impressive than its 13B-REW forerunner right away. A standard RX-8 will produce between 180 and 185 whp and 140 wtq on a dyno.
Around 225 whp can be produced by a normally aspirated Rx8, which is regarded as its maximum output. Bolt-on upgrades can bring your power up to about 210 whp. It will take more costly modifications, like engine porting, to increase power from 210whp to 225whp.
Any power output over 225whp will necessitate forced induction using a turbocharger. At 300 whp, reliability is ok, but at these power levels, you probably won’t get more than 10,000–15,000 miles out of the motor. A turbine can produce 400 whp, but this will require an upgraded engine and engine block.
The RX8 engine isn’t very tuner friendly generally. Adding power to an engine that already exhibits dependability issues only makes things worse. Reaching the bolt-on power limits of around 210 whp is fairly expensive, and aiming for anything greater is both very expensive and highly unreliable.
If that doesn’t concern you, though, check out our comprehensive guide to RX8 performance engine modifications.
Performance Modifications & Upgrades for the Mazda RX-8
The following are some of the top Mazda RX8 13B upgrades:
- Absorption of cold air
- Custom or flash song
- Catalytic converter
- Portable metronome
- Outflow and intake piping
- Superchargers and turbochargers
Every modification that can make the Rx8 more powerful will be the center of this guide. Other possibilities include switching to a 3-rotor configuration, swapping the LS, upgrading from 4- to 6-ports, switching to 13B-REW configurations, etc. All of these are bolt-on modifications that are doable for any novice, with the exception of modifying the intake and exhaust ports and adding forced induction.
This list, which is numbered from 1 to 9, does not necessarily reflect a ranking of the top mods. However, since porting and turbos are more significant modifications that call for extensive study before beginning, they are placed at the end.
1. Improvements to the RX-8 cold air intake
Cold air intakes boost output in two different ways. First, they eliminate the restriction caused by the original intake box and add more air to the engine through a bigger filter. More power is produced as a result of higher air pressure in the combustion chamber and intake system due to the increased air movement. Second, it moves the filter lower on the motor, allowing colder air to be drawn in. Power also rises because colder air is more flammable.
The power increases made aren’t quite as impressive, though, because the RX8 is a naturally aspirated engine. Nevertheless, when coupled with a tune-up and other exhaust changes, an upgraded intake will increase horsepower on the Rx8 by about 3–4 whp. The Rx8’s stock intake is actually quite excellent, so adding just an intake without any other modifications is probably not going to result in any power gains.
A K&N drop-in filter is an alternative to a complete intake system. Gains of about 1whp have been demonstrated for drop-in filtration. We typically only advise installing an intake system if you intend to add a tune and other bolt-on modifications because the cost of an intake system is quite costly compared to the power gains it offers.
Advantages of Rx8 Cold Air Intake
- 3–4 whp more
- Gains of 1-2wtq
- Pleasant swallowing noises
- Improved accelerator sensitivity
Improvements for the best RX8 cold air intake
- Speeding Rhythm
2. RX-8 ECU and Firmware Tuning
The most effective bolt-on modification for your RX-8 in terms of power increases will be a flash tune or ECU tune. To boost output and tame the power band, ECU tuning modifies the fueling, timing, and numerous other engine variables. The Cobb Accessport is the top product available for the Rx8.
To boost power, the Accessport merely plugs into your car’s OBDII port and re-flashes the ECU. It is detachable and plug-and-play. It comes with a selection of default songs designed for varying power objectives and installed modifications.
Despite having the same original ECU, not every 13B Renesis has the best tune. Because each engine differs marginally from the next, the factory tune behaves differently when installed on each engine. Some motors are simply not tuned properly at first. All of these factors will be adjusted by an Accessport tuner to work in harmony with your engine and produce a faster, more potent, and more dependable engine.
While your RX8 will gain some power when you plug in a regular Accessport, custom tuning will give you the biggest benefits. The effects of modifications on an engine’s operation, including fueling and AFRs, are numerous. The stock tunes that arrive with an Accessport may not be tailored for your engine and your custom modifications. Therefore, one of the greatest improvements you can make to your Accessport is to get a custom tune.
I advise having a custom tune only when it is absolutely essential given your mods or once you have finished adding mods to the vehicle. Every new mod you install changes how your engine operates, necessitating a new custom tune. It is the only tuner we advise because almost all custom tuning companies base their tuning on the Accessport.
Advantages of RX-8 ECU Tuning
There are advantages to modifying the RX8 13B rotary engine:
- Gains of 8–10 whp and comparable torque increases
- Better output curve
- Motor performs better and is consequently more dependable.
- Plug-and-play and quick to uninstall and modify
3. Upgraded Mazda RX8 Headers
The exhaust system’s headers are its first part. The exhaust gases are directed to the midpipe, which contains the catalytic converter, and they bolt directly to the block. Headers are solely an aesthetic modification for a stock RX-8 because they don’t add much performance to the engine. However, when combined with a complete exhaust system and a tune, headers can offer some respectable power increases.
More exhaust gas is produced as a result of the engine receiving more air and producing more electricity. As soon as air and electricity are present again, the stock headers become constrictive. As a result, the exhaust system experiences more backpressure, which can force exhaust vapors back into the combustion chamber and affect AFRs. A more modern header produces more power by reducing backpressure. It also brings down exhaust gas temperatures, which are already too high for these motors.
Short tube or long tube heads
One word of warning: headers make the Rx8 quite noisy. especially when paired with a full exhaust system and a midpipe without a cat. On my Rx8, which had original headers, I had a custom straight-piped exhaust, and it was brutal. There is nothing worse than driving a vehicle with 190 horsepower and hearing it sound like it should have 1000 horsepower.
Advantages of the RX8 Upgraded Header
The following benefits of RX8 header upgrades:
- Gains of about 5whp with extra modifications
- Increased exhaust sound
- Less backpressure in the tailpipe
4. RX-8 Midpipe Catless Modifications
The midpipe is the next component of the tailpipe after the headers. Because it contains the main catalytic converter, the midpipe is the most constrictive component of the exhaust system. The only way to upgrade the midpipe if you want to increase power is to use a catless midpipe. Even though it’s strictly against the law, there are some advantages.
Since the stock cat does an excellent job of reducing noise, getting rid of it will make the car noticeably louder. The straight conduit is option A, which I don’t advise because of how loud it will be. Purchasing a midpipe with a solitary resonator is option B. Purchase one with two resonators for the best sound quality and final choice. The raspy exhaust sound brought on by removing the cat will be lessened by the dual resonators. You will need a Cobb Accessport or other adjusting device to code out the CEL because this will result in a P0420 engine code.
Since they are forbidden today, catless midpipes are quite rare. Choosing a high-flow selection is the alternate choice. High-flow midpipes retain the original catalytic converter but switch it out for a less constrictive model. However, the RX8’s exhaust gas temperatures are so high that they ultimately burn through the catalytic converter, effectively rendering it catless. Cats in high-flow choices mean that they will yield smaller power increases.
In addition to being against the law, it also causes your exhaust to smell bad, which is obvious at idle.
Advantages of Catless Midpipe Performance
- Gains of 5-7whp
- Very little power increases
- Less backpressure in the tailpipe
- Increased exhaust sound
Excellent RX8 Midpipes
- Speeding Rhythm (dual resonated)
- Bureau Authority (dual resonated)
- BHR (single resonator) (single resonator)
- TurboXS (straight line or high-flow) (straight pipe or high-flow)
5. Modifications for RX8 Catback Exhaust
A complete header-back exhaust system will increase the RX-8’s power by 12–13 whp. Although the midpipe and headers account for the bulk of these gains, the cat-back section of the exhaust does contribute a small amount of exhaust horsepower when used in conjunction with the midpipe and headers. A cat-back will only add sound to an entirely stock vehicle and won’t actually increase power.
are the two available choices. The power gains from long tube headers will be marginally superior, but they will call for an aftermarket midpipe. While offering slightly less power gains, short tube headers can be mounted straight to the factory midpipe.
Further backpressure reduction results in catback power increases. Out of all the exhaust components, this one offers the tiniest gains because it is the least restrictive to begin with and is located the farthest from the exhaust ports.
The most important factor in choosing a cat-back exhaust system is sound. They all accomplish the same goal and offer roughly equivalent strength increases. For instance, TurboXS is the loudest muffler on the market, whereas Racing Beat and Agency Power are a little more subdued.
Performance Benefits from Cat-Back Exhaust
- Increases of 2-4whp
- Small power increases
- Less backpressure in the tailpipe
- Increased exhaust sound
RX8 catback exhaust upgrades ultimately result in some power increases and other advantages. The midpipe, catback, and headers can all be modified to produce a very powerful 13B, though. The headers and midpipe are where you’ll see the greatest power and performance, so you might think about choosing just one or two of these choices.
Optimal RX-8 Catback Exhausts
- TurboXS (really strong) (really loud)
- Bureau Authority
- Speeding Rhythm
- Borla, GReddy, HKS, etc.
6. RX8 Changes to the Lightweight Flywheel
When the accelerator is not depressed, the motor and flywheels provide rotational inertia. Without a flywheel, the engine would cease spinning and shut off if you let go of the accelerator. When you take your foot off the gas, the flywheel remains spinning, which maintains the engine running.
The flywheel can be upgraded to increase propulsion and speed without necessarily increasing power. The flywheel functions as a force opposing the engine because it rotates along with the crankshaft. The flywheel can be improved and made lighter to enable the engine to spin more quickly and achieve redline more quickly.
Although it doesn’t increase strength, it does improve responsiveness and hasten redline. While a rx8 with a lighter flywheel will likely accelerate from 0 to 60 mph more quickly, it will dyno at the same figures as one with a stock flywheel. This is a wonderful modification because most people are more interested in how quickly their car goes than in how much power it produces.
The flywheel’s weight reduction will increase the engine’s responsiveness. On the other hand, it does somewhat affect drivability. The motor now revs up and down more quickly, which can make starting uphill more difficult.
Advantages of a Lightweight Flywheel
The following advantages of RX8 lightweight flywheel upgrades:
- Improved throttle and engine reaction
- Revs higher
- Better propulsion
7. Improvements to the Mazda RX8’s Lightweight Pulley
The upgrade of the pulleys is a weight-reduction change, similar to the upgrade of the flywheel. Three distinct pulley systems are present in the RX-8, one for each of the water pump, generator, and crank. Underdrive pulleys make up the bulk of RX8 pulley kits. Under drive refers to slowing these pulleys down so they use less of the crankshaft’s power by decreasing the speed at which they rotate. Therefore, you are 1) lessening the pulley systems’ weight and 2) slowing down how quickly they spin or move.
The drawback of pulleys is that they have an adverse effect on all of the systems they pull, and the weight decrease isn’t particularly significant. For instance, it’s not a big problem to underdrive your air conditioning system, but underpowering your alternator can harm your battery and electrical systems and can cause your car to overheat.
For what it’s worth, many RX8 users advise against using pulley upgrades. Except if you want the cool look inside the engine bay, the power increases are negligible and the reliability risk isn’t worth it.
Pros and Disadvantages of the RX8 Upgraded Pulley
The following are some benefits and drawbacks of Mazda RX8 gear upgrades:
- Gains of 1-2whp
- Accelerated throttle reaction
- Better propulsion
- Underdrive harms the water pump and battery.
- A weaker cooling system
- Inferior power steering
In the end, pulley modifications have few efficiency advantages and a few drawbacks. If you want to maximize power and response, it might be a decent 13B upgrade. We do think there are much superior RX8 upgrades out there, though.
8. Renesis 13B Inlet & Exhaust Porting
The 13B engine can be ported similarly to how piston engine cylinders are ported. To enhance airflow into and out of the combustion chamber, it entails enlarging the intake and exhaust openings. Since the ports are situated on the rotor housings, an engine must be fully disassembled before being ported. Because the engine must be removed, disassembled, and then put back together, performing it is quite costly. But if you’ve already disassembled your engine, porting it won’t cost you much because all that’s needed is some tooling work on the standard rotor housings.
We don’t advise anyone who isn’t pursuing high power levels or using their Rx8 for racing applications to port their engine because it is an advanced subject. Street ports, bridge ports, and peripheral ports are the three main categories of 13B porting. High horsepower racing apps typically use bridge ports and peripheral ports in particular.
Here is a useful overview of the RX8’s porting options since we won’t go into too much depth in this article.
If your engine is already being repaired or if you already have forced induction and want more power, we only really advise porting your engine. In this situation, turbo kits are more cost-effective than porting, so we advise going that way first.
Improvements in RX8 Porting Power
Depending on the style of porting used, modifying the intake and exhaust ports can result in significant power increases. The RX8’s power improvements are broken down as follows:
- 15 to 25 whp for street port
- 30–40 whp for bridge ports
- Port Peripheral: 50–60 whp
9. Turbocharger and supercharger kits for the Mazda RX8
Forced induction is where the 13B Renesis engine’s true power gains are found. Beyond 210whp, a naturally aspirated RX8 is challenging and costly to modify. With turbo and supercharger kits capable of generating 300-400whp, forced induction is the simple way to make significant power gains.
Check out this discussion if forced induction is something you’re interested in. Since there is really only one supercharger system available for the RX8, produced by Pettit Racing, with prices starting at around $7k, turbo kits are more widely used. It takes a lot of knowledge and comprehension of the 13B and forced induction to decide whether to install a turbo. We will reserve the details for a different RX-8 turbo upgrade guide because this is a fairly extensive subject.
The GReddy kit is arguably the most well-liked and affordable kit, with prices beginning at around $5k. The kit’s only real drawback is that it can only produce about 275whp. There are other kits out there that can generate more electricity than 400whp.
I wouldn’t even consider installing a supercharger in your Rx-8 unless you have $10k or more lying around. The kits are pricey, and you probably won’t be able to construct anything for less than five figures even with supporting modifications. Additionally, it has some significant stability issues.
Performance Improvements for the RX8
The 13B Renesis engine can acquire the most power by tuning it and getting rid of the catalytic converter in the midpipe. The combined output of an intake, pipes, and a catback exhaust system is about 10whp. Upgraded pulleys aren’t very useful, and lighter flywheels improve acceleration but don’t boost output.
20 to 30 whp can be added overall by adding an intake, a tune, and a complete header-back exhaust system. With a standard RX-8 dynoing in the 180–185whp range, you are looking for a “full bolt-on” RX8 to have around 200–215whp.
The maximum output for a 13B engine without more severe porting or forced induction is thought to be around 230whp when you add a street port to the engine. Aggressive porting, such as a peripheral port, can produce figures of about 260 whp, but this modification is neither cost-effective nor user-friendly. The addition of forced induction results in the greatest gains at the lowest expense.
The Rx8’s safe power range when turbocharged is between 275 and 300 horsepower, but dependability at these power levels is still probably only good for about 10,000 miles. Upgrades to the block/rotor housings as well as numerous other internal changes and upgrades will be necessary to reach 300whp.
The best modifications for the RX8 are definitely those that relate to appearance and suspension/handling, such as upgraded RX8 coilovers, unless you have $10k+ to spend on this vehicle. Trust me when I say you don’t want to be the man with the loudest car on the road only putting down 200whp because I had a straight-piped RX8.