Tuning the Mazda 13B

"Comprehensive guide to tuning the Mazda 13B engine!"

We are always getting posts requesting information on the best tips on 13B modifications. So let us look into Mazda 13B modifications and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mazda 13B are popular tuning projects and with a few sensible uprated enhancements like a remap, turbo upgrades and camshafts you will greatly increase your driving fun.

This pages aim is review 13B tuning and summarise the greatest upgrades.

When talking about the top parts for your 13B engine, we are going to concentrate on the parts that give the best power gain for you spend.

NB: On a Rotary engine you need to allow air to get into the engine as fast and smoothly as possible so porting the engine and increasing the turbo are the primary methods used by tuners.

Gear walk issue on 13B engines

Gear walk can be an issue on rotary engines. Pre 1985 Mazda used 9 pins, and after this they increased that to 12 pins, but on highly tuned engines you can still suffer from gear walk. Aftermarket tuners have come up with innovative methods to prevent the rotors gear separating from the body of the rotor at high RPMS and with high engine temperatures.

Rotary engine tuning issues

Seals around the engine also need to perfect if you are serious about increasing power. Instead of going with oversized seals make sure the rotor is perfectly flat, and this requires a specialist as most machine shops will not be able to work to the tolerances required.

On a heavily tuned rotary engine, you'll see higher internal engine speeds, faster spool up times and more heat generated, this requires a fresh look at oil supply. We recommend a race spec dry sump oil systems installed on these to accomplish this.

You should ideally match your bhp range to your typical driving style so for a car used daily stick with a mild fast road 13B camshaft

The ecu map and injectors and fuel pump also will say much on the torque gains you'll hit.

13B Best Tuning Mods & Upgrades

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Guide to the best tuning mods & Upgrades

  1. ECU Map Tuning & Remaps

    The Rx8 requires an aftermarket ECU to change the OEM map, but remapping is the most vital step of your tuning project to fully maximise your mods. Expect 10-20% on NASP engines and 30-40% on turbocharged units.

  2. Strengthen Your Engine

    Tuned cars will show up weaknesses, typically in the turbochargers, clutch and internal engine components. Whilst most engines can cope with mild tuning mods, TorqueCars recommend that you upgrade the internal components before these weak spots manifest themselves.

  3. Mods that Remove a Restriction

    A restricted intake or exhaust will have an impact on your performance, so use a better flowing air filter/induction kit and better flowing exhaust (sports cats where legal are a good option) whenever your tuning creates a flow restriction. Turbo engines also benefit from intercooler upgrades as these resist heat soak for longer periods of time.

  4. Mods that Improve Fuelling

    Every tuning project will aim to increase the air supply, but fuel supply is just as vital and will need to match the air the engine can utilise,  a fuel pump and injector upgrade are usual mods, but also in many cases the fuel regulator will need improvement.

  5. Mods to Provide better Airflow

    Increasing the air supply is just as essential as improving fuelling, we suggest you look at head mods (flowing and porting, 5 angle valve jobs), fit bigger valves, fast road cams and forced induction upgrades (adding a better flowing turbo) to improve air intake.

13B Tuning Stages

Stage 1 13B modifications: Remaps/piggy back ECU, Sports exhaust manifold, Drilled & smoothed airbox, Panel air filters, Intake headers.

Stage 2 13B modifications: induction kit, Ported and polished engine, high flow fuel injectors, fuel pump upgrades, Sports catalyst & performance exhaust.

Stage 3 13B modifications: Internal engine upgrades (flowing the ports/big valves), Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions, Engine balancing & blueprinting

Plan your options and then acquire your parts and set yourself a power target to avoid costly mistakes.

A remap will help unlock the full potential of all the upgrades you've done to your 13B.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output often rely on the upgrades you've fitted and the condition of your engine.

Feeding more air and fuel into each cylinder is the main goal to any tuning task.

Headers take the air from the intake filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Intake headers can make a big effect on to fuel mixing and power on the 13B.

Commonly we find the intake headers are begging for aftermarket parts, although a few OEM provide reasonably good intake headers.

Adding a 13B larger valve kit, doing some port matching and head flowing will also boost performance, and as an added benefit will raise potential for increasing the performance increase on other mods.

Turbo upgrades for the 13B

NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your 13B

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes massive power gains.

If your car has forced induction upgrades are relatively easy and you'll see that turbocharged engines are made with many forged and stronger components.

However every engines will have power limits

Discover these restrictions and fit stronger pistons, crank and engine components to survive the power.

We've seen people spending a fortune on turbocharger upgrades on the 13B only to see the whole thing go up in smoke just after it's used on the roads.

Bigger capacity turbo chargers will usually suffer a bottom end lag, and smaller turbo chargers spool up much more quickly but don't have the top end engines power gains.

We are pleased that the market of turbos is always evolving and we commonly find variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust gases into a couple of channels and flow these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

It is not unusual that there's a limitation in the air flow sensor MAP/MAF/AFM on the 13B when a lot more air is being pulled into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited power at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more difficult to setup. We have this article covering twinchargers if you want to read more.

Uprating 13B fuel injectors

You will need to ensure that the engine is not starved of fuel so should look at the fuelling when you start extending past 20% of a torque increase.We would recommend you to over specify your injectors flow rate.

Bosch and Tomei fuel systems are popular on RX7 projects and for good reason, they also cope well with the fuel requirements at 13lbs or more of boost quite capably.

As a rule of thumb add 20% capacity when fitting an injector, which takes into account injector deterioration and gives a bit of spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Best 13B performance exhausts

You should look to improve your exhaust if the existing exhaust is creating a restriction in flow.

The 13B exhaust gets very hot and in some race situations the exhaust has been known to increase in length by a surprising amount, so quality counts here. Getting  a cheap exhaust is a false economy as it just won't last.

On most factory exhausts you should find that the exhaust flow rate is good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Please don't run with the largest exhaust you can find this will slow up the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions are in the catalyst and filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

13B Engine power performance & applications

13B-RESI

1984–1985 Mazda HB Luce
1984–1985 Mazda HB Cosmo
1984–1985 Mazda FB RX-7 GSL-SE

13B-DEI

1986–1988 Mazda FC3S S4 RX-7, 146 hp (109 kW)
1989–1991 Mazda FC3S S5 RX-7, 160 hp (119 kW)
1986–1991 Mazda HC Luce Turbo-II, 185 hp (138 kW)
1986–1988 Mazda FC3S S4 Turbo RX-7 Turbo-II, 185 hp (138 kW)
1989–1991 Mazda FC3S S5 Turbo RX-7 Turbo-II, 200 hp (149 kW)

13B-RE

1990–1995 Eunos Cosmo, 235 hp (175 kW)

13B-REW

1992–1995 Mazda RX-7, 255 hp (190 kW)
1996–1998 Mazda RX-7, 265 hp (198 kW)
1999–2002 Mazda RX-7, 280 hp (209 kW)

13B-MSP (Multi-Side Port)

The Renesis replaced the Wankel  and offered (211–235 hp) giving about 50% more efficiency over the previous design.

2003- Mazda RX-8 157–175 kW (211–235 hp)

Problems and issues to look out for on the 13B

The 13B engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the 13B, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your 13B engine please join us in our friendly forum where you can discuss tuning options in more detail with our 13B owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our 13B guides and tips are kept up to date.

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