RX8 Tuning Tips

"The Renesis Renaissance"

Mazda had great success with the RX7 and proved that a rotary engined car can be fun to drive. The successor came in the form of the lovely RX8. It was leaps and bounds better than the RX7 in many respects.

The angular lines, edgy design, and interior trim all won the hearts of RX8 around the world. Mazda updated the 13b Wankel engine creating the innovative Renesis rotary engine.

Tuning the RX8 rotary engine is considered difficult by some but there are a few options that can transform the RX8 performance. Bear in mind that these come from the factory in a pretty highly tuned state, so end user improvements are smaller than they would be on a run of the mill production car where little attention has been made to tuning them up.

The RX8 comes from the factory in a pretty highly tuned state, so end user improvements are smaller than they would be on a run of the mill production car!

The benefits of a rotary engine include the ability to provide high rpm tolerances and a silky smooth power delivery.

Problems though include a lack of low down torque at low RPM but when driven correctly these cars have a lot to give. Standard power figures of around 200bhp from a 1300cc engine really push the envelope of what is possible.

Ignore the horror stories of unreliability, if people don't know how to care for a Renesis engine and treat it properly it will respond with problems.

Hopefully, by the end of this article, you'll have an understanding of this engine and be better prepared to extract more power and care for it.

Best Engine Mods for your RX8

We will look at these in detail in this article and cover some of those important points you need to know about the Renesis engines and how to care for them whilst tuning them up.

  1. Handling - suspension and weight reduction
  2. Brake upgrades - making the RX8 stop better is vitally important
  3. Differential upgrades - getting the power down should not be overlooked and a good diff can improve cornering and acceleration
  4. Lighter flywheels - this allows the engine to spin more freely and works well on a rotary engine like this
  5. Remapping - the ECU controls so much of the engines output that great gains can be had with just a remap
  6. Porting and Lapping - a special rotary only mod, that improve power and the torque curve
  7. Improve fuelling - injectors and throttle body upgrades
  8. Intake and Exhaust mods - air flow through the engine are important and the aim here is to avoid a restriction
  9. Weight Reduction - this will improve handling and performance on your RX8

RX8 Handling mods:

RX8 Suspension tuning

Your RX8 tuning should start off with some improvements to the handling and brakes. Your first job is always improving the bushings, as these wear out and the suspension really starts to suffer from the extra play.

Setting a little negative camber on the fronts and around 1 to 1.7 degrees of toe in for increased stability or toe out for improved cornering typically improves the handling and cornering of your RX8.

See our video about improving your handling, where we go into choosing and setting up suspension.

Upgraded RX8 Suspension bushings

Bushes are a rotating rubber mount that enables the RX8 suspension components to connect to and spin around the chassis of the vehicle. The rubber ones will eventually disintegrate.

A new set of OEM rubber bushings may significantly enhance your vehicle's handling.

New polyurethane bushes last longer and retain much tighter handling, albeit they may make the ride a little bumpier due to their increased durability.

Additionally, the increased vibration and play may exacerbate the depreciation of other suspension components.

By eliminating the excessive play associated with rubber bushes, a set of new poly bushes will enhance your car's handling.

While the majority of aftermarket bushing kits include a whole set of suspension bushes, rarer vehicles and older models may only have the primary bushes available in polyurethane.

Often, special bushes may be made to meet your specific requirements.

Suspension Springs Dampers and Settings

While improving the handling of your RX8 is often the first goal in your auto tuning effort, we frequently see the same errors repeated.

Therefore, if your car is also a daily driver, what factors should you consider while configuring and choosing your suspension?

Purchasing a non-adjustable suspension system that lowers the car 30mm from a neighbourhood component store and expecting it to be the optimal configuration is a typical misunderstanding.

Improving the cornering is achieved with a slight drop in ride height, slightly stiffer springs and strut braces, and roll bars.

You only need a small drop, many people go too low and this hampers the cars handling on rough road surfaces and over pot holes and speed humps.

A set of coil overs will do nicely as these allow you to fine-tune the ride height and spring rates, to suit your driving preferences.

Some RX8 suspension brands to consider:-

  • Tein
  • YSR
  • MeisterR
  • KW Variant 3

Wheel spacers are a bit of a bodge but they do help increase the car's track width and improve things, but you are adding weight. Always make sure you get the correct bolt lengths and we would recommend the Eibach spacers as they are quite well made.

The car can be lowered around 35 mm. We would recommend adjustable suspension so you can set the damping and spring rates to suit your driver preference.

RX8 Brake Mods

A big brake conversion kit will really pay dividends and give a progressive brake feel.

Larger brake discs are the first thing that comes to mind when discussing brake modifications, but don't forget about the pads - they are arguably more vital than the discs, and faulty pads may damage your car's handling.

Brakes are essential since traveling rapidly necessitates the ability to stop quickly! A brake works by rubbing a friction pad against a disc to convert kinetic energy into heat.

The dissipation of this head slows the car's forward velocity. Excessive braking generates brake heat, as observed in night time racing, when the brakes flare with heat after intense usage.

Because the pad transfers braking heat throughout the discs, the cooler the disc, the better.

The vented disc's middle channel increases the surface to air ratio of the disc, resulting in better and quicker cooling.

Drilled discs help keep pads "clean and sharp" by boosting the air ratio and reducing gas buildup between the pad and the disc. Larger discs result in improved cooling, however, they may demand a different alloy wheel if there is not enough clearance or space.

RX8 Brake Pads

Material for the pads. High friction brake pads, however, are required, even if they cause noise and dust.

Racing pads are constructed with a high friction compound that performs best at higher temperatures.

Because racing grade brake pads only operate when they are very hot, they are unsuited for use on the road, where braking is done on cold pads or in short bursts.

TorqueCars has concluded that Pagid and Black Diamond fast road pads are a good balance between braking and wear.

Some RX8 performance brake pads generate practically no brake dust and last longer than the standard pads I was using — albeit driving style may influence pad and disc wear.

Torquecars recommends if you are not a mechanic, you leave your RX8's brake maintenance to the pros to prevent accidents this is one area you don't want to be messing with.

The stopping power of a vehicle may be enhanced. Normally, you would replace the discs and pads. Because a bigger disc has greater friction and disperses more heat, you will notice an immediate advantage.

With a huge RX8 brake disc conversion kit, you will have more braking sensation and will be able to discern the moment of lockup more easily.

Following that are calipers (which provide clamping force) and pistons (which push the calipers). The greater the number of pistons, the greater the clamping power, enabling you to use bigger pads.

The stock master cylinder may need to be overbored or replaced with a bigger one to match the capacity of the donor vehicle's master cylinder.

Increase the pad, caliper, and piston count to enhance the impact of upgrading the discs.

Please watch our video which covers the best brake upgrades for your car. Be sure to subscribe and support our new channel.

RX8 Differential mods (Limited slip diffs/LSD's)

The trouble with a road car is that the diff will transmit more power to the wheel that is spinning the fastest.

If one wheel is on ice while the other grips, all torque will be sent to the wheel with no grip, and the car will get effectively stuck. This is where the torque sensitive slip diff comes in. (Torsen)

This will function similarly to a standard but will limit the amount of power going to one wheel to 65-80 percent depending on its design.

This prevents the RX8 from being stuck in low grip circumstances and actually improves traction when navigating wet turns.

We also have a torque actuated (clutch type) LSD that detects the amount of load from the input and functions as a 1 way 1.5 or 2 way limited slip diff, providing a good overall compromise.

As the load is fully applied, the coupling is proportional, and when the load is reduced, the coupling becomes fixed.

Geared torque sensitive diffs are also available, which look at the relative difference between the output shafts rather than the input shaft but have come into their own on in FWD cars decreasing torque steer and on drift car settings allowing more predictable oversteer, but pro drifters prefer a clutch type LSD or locked differential.

The electronically controlled slip diff is a relatively new device that employs anti-lock brake sensors to monitor independent wheel speed and applies brakes to bring the wheel under control if it begins to slip.

When you install a new LSD, you must follow the instructions that came with it to properly break it in, or you risk causing irreparable damage to the diff.

TorqueCars.com recommends using the Ford 8.8  LSDs for motorsport and high speed road use because of their sturdy construction and dependability. Conversion kits and modified differential covers are available for the RX8.

Best RX8 Engine mods

The RX8 engines need to be properly looked after and serviced regularly. Do not let the unusual rotary engine design and configuration put you off. These are much better than early rotary engines and are every bit as flexible and reliable as a reciprocating piston setup.

For a casual tuner, a remap is one of the best mods you can do, but let's dissect this awesome engine and see what the other potential mods are for it.

We've seen some benefits from fitting a lighter flywheel to the earlier engines, this is something Mazda did on later models anyway, and it frees up the engine to respond to rev changes more efficiently.

A NASP RX8 is just crying out for a turbo conversion and this is probably one of the few "bolt on" options although it can prove expensive and engine swaps are usually an easier route to go.

A turbo will raise the standard power to around 400bhp! Sadly in the real world, there is a lot more to it than just bolting on a turbo. A whole host of other components will need uprating and strengthening and the mapping will need to be spot on.

The 4 port RX8 engines are more suited to turbocharging than the 6 port ones but both conversions require a lot of work and planning and we would not recommend undertaking this unless you have obtained a full kit and have facilities to set up and create a custom map.

Obvious power mods for a turbocharged RX8 would include a larger front mounted intercooler. The intercooler can suffer from heat soak on long runs so channeling lots of fresh air through this will pay dividends. Power can also be increased with the addition of a larger turbo or a turbo with higher performing internals (a hybrid).

RX8 engine bay heat build up solutions

Engine heat build up is a massive problem when adding forced induction and a larger oil pan and even an oil cooler will help address this issue. It would also pay to get the exhaust down pipes coated or wrapped to contain the heat.

The RX8 engine runs pretty hot anyway, so anything that helps bring temps down is a good thing.

Further engine cooling mods will include an uprated water pump and thermostat, and use of a synthetic water cooler additive with some high performance silicone hoses to avoid leaks from higher pressures.

Lighter flywheels on the RX8

The hefty wheel between the engine and the gearbox rotates storing kinetic energy as it rotates.

This reduces engine speed changes, which is good for cruising but bad when you require a rapid engine response.

With a lighter wheel, the engine has less strain and can rev faster, producing greater power. A race-tuned engine revs up and down significantly quicker. Inertial spin is reduced with a lighter flywheel, especially on slopes.

With a lighter flywheel, you lose momentum faster on a hill. However, a hefty flywheel maintains engine motion, but the hill reduces power and the RX8 will slow up.

This allows for maximum torque and unrestricted revving and makes the car feel so much more responsive. BUT if you go too light on the street, your tick over will suffer. Discuss your application on the TorqueCars car forums.

RX8 Remapping Fuel Delivery upgrades

When pushing larger power gains you will also need to uprate the fuel delivery system to prevent the engine from running lean - if anything these engines prefer to run rich.

Initially, on the RX8, there were 6 injectors used, a total of 3 for each rotor, and a later revision changed this to 4.

A fuel pressure regulator upgrade will give you a more crisp throttle response, and greatly improve performance, but if you are pushing up the power consider upgrading the fuel pump, a 400 or 530 liter per hour kit should prove sufficient for most projects.

Throttle bodies are electronically controlled which allows the ECU to control the air/spark and fuel much more precisely, and this improves economy but also offers more tuning potential.

RX8 Remaps

We have looked remaps for the RX8 and sport chips without much success in certain areas, but there are some mappers out there, and you'll typically push the power from 228hp to around 246hp. Hopefully, RX8 remaps will become more widely available everywhere.

Thankfully here in the UK we have quite a few options but if you can't find an RX8 mapping specialist the best option is fitting a full aftermarket engine management system.

Avoid piggyback solutions, the stock RX8 ECU will work out something is going on and turn things back down in response.

You might want to look at MazdaEdit and VersaTuner as these offer decent gains.

This allows you to fine tune the timing and fuel delivery for the maximum power gain and this will also allow you to factor in any other mods you have done. On a standard car with an aftermarket engine management system, you can see power gains of around 2-5%.

Tuning tips and articles

Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Internal RX8 engine mods

Porting and Lapping

Porting the Renesis engines, if done properly, can have a big impact on the power delivery and torque curve. This is not a simple job though and is only really worth doing if you are already stripping down and rebuilding your RX8 engine.

Lapping the flat housings and adding high quality ceramic seals are considered important mods here, and dynamic engine balancing will also help you reach higher power gains retaining reliability.

Renesis Intake and exhaust upgrades

RX8 Intake mods

The setup on the RX8 flows pretty well, as you would expect for an engine that revs to infinity. There is very little gain by adding an induction kit.

Sucking in warm engine bay air will even sap power.

But if you fit the very best flowing air filter sited in a box with a good cold air feed you will only see 5-7hp of a gain at the top end.

So considering the cost of these parts, we really can't recommend it as an upgrade for your RX8.

RX8 Exhaust mods

A sports exhaust and induction kit can help provide power gains a little, but in the opinion of TorqueCars members, the standard setup is pretty good and gains are only noticeable high up in the RPM rev range.

There are not many 200bhp NASP 1.3 engines out there so you have something special in the RX8 and the nature of the way the engine works means it is ideally suited to hydrogen as fuel! (Perhaps this dream may become a reality one day but for now, I guess we have to stick with petrol!)

Adding a sports cat will also free up a TINY bit more power, on the Renesis these little gains all add up quite effectively.

Mazda did a good job, and in an engine that revs well over 7000rpm they needed to ensure the exhaust flowed really well.

Early cats on the pre 13B MSP were prone to clogging issues, the later cats were much better suited to the Renesis.

Don't go the decat/catless/test pipe route, because it renders the car illegal in most areas and the power gains and risk are not a viable proposition in our opinion.

For offroad only situations, and track work then you want to wring out every bit of performance but realistically the cat is only sapping around 5% of your power, and a performance cat will quickly restore this.

Weight reduction on the RX8

Cars that are lighter are faster and handle better.

Obviously, removing the seats, carpets, radio, seat belts, headliner, and air conditioning makes the family vehicle unusable.

Incorporating a few bean bags for the kids to sit on won't add much weight (Please notice that this isn't legal or safe).

Chart showing RX8 tuned to various power figures and quarter mile times, compared to weight reduction of 200kg's.

Horse Power
HP
Weight
Kg
RX8
Quarter mile
200 1400 15.28
220 1400 14.82
240 1400 14.41
270 1400 13.87
300 1400 13.41
200 1200 14.54
220 1200 14.1
240 1200 13.71
270 1200 13.2
300 1200 12.77

Lighter cars accelerate, corner and stop better with a 200kg weight saving giving the same performance boost as a 40hp increase, which also improves handling and braking!

To conserve weight, remove the glass windows and replace them with Perspex alternatives. For obvious reasons, replacing windows with Lexan or Plexi should save weight.

The most lightweight and strongest replacement body panels are carbon fiber. Lifting a car's hood reveals how heavy the panels are, thus removing as much metal as possible may save a lot of weight.

Also, before drilling or attaching fasteners, always test the panel on the vehicle for size.

A roll cage adds weight but may save lives and enhance handling by keeping the automobile stiff. It is possible to remove more metal from the automobile with a roll cage but not the structure.

If you know what you're doing, you can lighten many other metal pieces by drilling holes in them. Alloy wheels assist cut weight further. Lighter wheels are better for shifting direction due to rotational forces. Most magnesium alloy wheels increase brake airflow and stopping.

In addition to removing the door hinges and locks, the welding process strengthens the body shell of the automobile by adding additional strength. Even when replacing items like brake pads or discs, it's recommended to weigh them beforehand.

As many engine components as possible should be lightweight e.g. alternators, water pumps, fly wheels, pistons and blocks. Saving 200g in 5 different locations decreases weight by 1KG.

Note when tuning a Renesis engine

Ignition coil failure is common, primarily because these work really hard.

Keep an eye on oil consumption and frequently renew the oil, a rotary engine will use more oil than most conventional motors.

Reducing the weight of the flywheel to around 9 lb's seems to be a popular choice and does change the nature of the engine quite a bit, but we should add not always to the taste of drivers, try one fitted to an RX8 first before you commit yourself here.

Check the compression of your engine, it's a good way to spot potential problems before they get too expensive, and if buying an RX8 I would insist on a compression test before I handed over any money.

Why not join our friendly forum and swap tuning ideas and share pics of your RX8 with our other members.

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12 Responses to “Tuning the RX8 rotary”

  1. fadzilah says:

    my plan want to add jdm turbo kit to my mazda rx8,what else?item ADd.

  2. Matt says:

    The renesis engine is still a Wankel engine. Named after the Felix Wankel the German engineer responsible for the design. The renesis is simply a revised 13b

  3. ray says:

    i added a intake and a sports exhaust,and its back firering on the highway about 4000rpms , is there a place close to cincinnati that i can get it fine tuned

  4. brandoW says:

    Dude, its gonna back fire. Thats just a one of the quarks of the renesis. It runs rich, leaning it out would do more damage than good.

  5. Norman Grant says:

    My Local RX tuning specialist Re-Works tell me that it is not possible to tune a RX-8 ???

  6. Darren says:

    Absolute rubbish you can easily tune a rx8 if you have the money.simply putting on a full blower rather then a turbo will see massive gains once set up correctly.Re.Work talk out of their backsides I’m afraid.Take a look at some American tuning sites for the rx8.Say no more.

  7. jake says:

    I have a 2005 rx8 inside compartment by the clutch pedals is getting hot any body knows what wrong

  8. Paul says:

    What consists of fitting a turbo to the rx8

  9. Ben richardson says:

    Hi ive got a 08 rx8 and she just got 100 thousand on engine, i love the handling even as stock. Rensis i need more power was thinking about track meets and drifting in future. Should i just go back to racing bridge port turbocharged or rebuild 4ensis

  10. kas says:

    I would say the rx8 is already a higly tuned car out the factory, just like a civic type r there are only small hp gains to be had from tuning and bolt ons, if your looking to stay NA I would say focus on handling, light weight and driving feel to be faster around a track. Turbo or 4-rotor conversions are the only way to get big power, however you need deep pockets and mechanical skills. There’s always Nos but thats not really a long term or reliable option.

  11. Dessycorry corry says:

    I have just bought an rx8 r3 with an stage 2 tune kn filter intake and big exhaust but Mel came on second day cat inefficiency would a sports cat be a better replacement

  12. Pablo Iglesias says:

    I’m new to the rotary world and will take all info and advice that I can get. I don’t want world record speed or power, just enough to have some fun.

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