Subaru Impreza WRX Gen4 Tuning

"All you need to know about performance tuning the Subaru Impreza WRX Gen4 engine!"

A site visitor asked questions for more information on the Impreza WRX Gen4 and how to tune it up and modify it, so this article has been assembled which covers our go to modifications that we rate and are the best upgrades you can do to this engine.

The fourth generation Subaru Impreza vehicles were offered from 2011 onwards.

If you are interested in modifying the performance of these cars, this article contains all of the information you will need to give your vehicle impressive performance.

Herein we consider Impreza WRX Gen4 tuning and point out the premier modifications. Subaru Impreza WRX Gen4 great bases for a tuning project and with the best modified upgrades like ECU maps, turbo kits and camshafts you will greatly maximise your driving experience.

We have articles covering tuning, mods and upgrades for the following models.

Subaru Impreza tuning, Impreza WRX STi mods, Impreza WRX Gen1 mods, Impreza WRX Gen 2 mods, Impreza WRX Gen 3 mods, Impreza WRX Gen 4 mods, Impreza WRX Gen 5 mods, (VA) WRX Mods

History of the Impreza WRX Gen4 Engine

Subaru has launched a sedan (GJ) and a hatchback (GP) of its fourth-generation Impreza as 2012 models. New models are fuel-efficient and lighter in weight as compared to previous generations. The wheelbase of the sedan was extended to make a spacious interior, giving the same dimensions as that of Subaru Legacy models.

Five gasoline engine options were available: 1.6 L FB16 H4, 2.0 L FB20 H4, 2.0 L FA20F H4-T, 2.5 L EJ257 H4-T, 2.0 L EJ 207 H4-T, and one diesel engine 2.0 L EE20 H4-T. The vehicles were fitted with 5-speed manual or 6-speed Lineatronic continuously variable transmissions.

Subaru also launched a crossover-styled model named Subaru Crosstrek or Impreza XV in 2012. Another VA series WRX was released in 2014 and named WRX S4 in Japan. This model was unique as compared to previous models in terms of the entire front-end design and rear quarter panels.

Tuning the Subaru Impreza WRX Gen4 and best Impreza WRX Gen4 performance parts.

Best Impreza WRX Gen4 parts

The best Impreza WRX Gen4 parts on an engine are obviously the ones that give the biggest return for your cash.

We are not fooled by common Impreza WRX Gen4 parts, they need to work out to be cost effective.

Tuning tips and articles


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


Please watch our video which covers the 5 principles of tuning your Impreza WRX Gen4. Be sure to keep up with our latest YouTube content and subscribe.

Best mods for your Impreza WRX Gen4

  • Upgrades to turbochargers and superchargers - forced induction is the most dramatic method to improve intake air supply, ensuring you are able to utilize more fuel and make higher power. Typically one of the most costly upgrades it offers big gains.
  • Remaps - A remap offers the biggest gains in terms of your investment, aftermarket ECUs, and inline Tuning boxes are all alternatives.
  • Internal engine mods - crank, pistons, conrods & compression ratio including balancing and blueprinting
  • Impreza WRX Gen4 Suspension Tuning - Tweaking your suspension radically improves your Impreza WRX Gen4 handling Poly Bushes and Coilovers are typically fitted to achieve this
  • Flywheel lightening - a lower mass flywheel will enhance the engines rev changes. In some cases flywheel lightening is not beneficial for all Impreza WRX Gen4 engines.
  • Intake Upgrades and Exhaust Upgrades - Note that on their own these mods will NOT ADD POWER in most applications, but they enable you to release power after other upgrades by losing a restriction.
  • Sporty Profile Camshafts are are often the best upgrade for an engine, but we recommend they be installed in your engine by someone who knows what they are doing and they are not always easy to source but you might have a local firm to regrind a stock camshaft .
  • Braking Mods - Enhancing your stopping power needs to be somewhere in your mods list.

Impreza WRX Gen4 Tuning Stages

Typical stage 1 mods often include: Sports exhaust manifold, New Bushes, Drilled & smoothed airbox, Performance Brake Pads, Fast road camshaft, Intake manifolds.

Typical stage 2 mods often include: Suspension (Sports), Brake Discs (drilled/slotted or grooved, Sports catalyst & performance exhaust, high flow fuel injectors, induction kit, Fast road cam.

Typical stage 3 mods often include: Internal engine upgrades (head flowing porting/bigger valves), Engine balancing & blueprinting, Twin charging conversions, Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Competition cam.

The first performance modification you should make to your Subaru Impreza 4th generation vehicle is to upgrade its air intake system. This is one of the most significant upgrades you will make to your vehicle.

These components can be quite costly. However, it is worth noting that the air intake system provides a significant performance boost.

This is because such air intake systems allow the vehicle's engine to gulp in more air.

When air and fuel are burned in internal combustion engine vehicles to generate power and torque, the higher the quantity of air, the better the result.

For the 4th generation Subaru Impreza vehicles here are two impressive options in this regard:

Using the Short Ram Air Intake System from HPS Silicone Hoses provides a performance boost of around 8 hp and 8 lb-ft torque;

Similarly, you can use the Cold Air Intake System from AEM Intakes through which you can increase the power up to 10 hp and torque up to 9 lb-ft.

  • Air Intake Filters

Another effective way of improving the flow of air to the vehicle is by using specially designed performance air intake filters.

The beauty of these performance air filters is that they are less restrictive in nature which means that they allow more air to pass through them.

Their price is quite reasonable. Still, the performance boost they offer is impressive. You can choose an air intake filter from one of the following companies:

  • COBB;
  • AEM;
  • APEXi;
  • HKS;
  • DC Sports.

Impreza WRX Gen4 Handling/Suspension Upgrades

Adjusting the handling is often the first step in using the Impreza WRX Gen4.Adjusting the Impreza WRX Gen4's handling is often the first step in tweaking it.


You can improve the ride quality of your vehicle by performing a wide number of suspension-related modifications.

Some of these include:

Lowering Kits

The purpose of installing lowering kits on your vehicle is to bring down the overall ride height.

This makes the vehicle look more appealing but the biggest advantage is that the centre of gravity of the vehicle is reduced which means that the cornering ability is significantly improved.

Choose lowering kits from one of the following companies for your Subaru Impreza 4th generation car:

  • Eibach;
  • Yellow Speed Racing;
  • RS-R;
  • H&R;
  • Pedders Suspension.


If you want to control the ride height of your vehicle with ease, we recommend that you go for coilovers. You have various options in this regard but the following companies offer some of the best parts.

  • HKS;
  • Megan Racing;
  • TEIN;
  • D2 Racing;
  • TruHart.

Coilovers are quite expensive and thus you must ensure that the whole installation process takes place according to the manufacturer’s guidelines.

Coilovers allow you to lower or raise the car and this allows you to setup your cars handling.

One of the most popular reasons for tweaking your Impreza WRX Gen4 suspension is to improve its cornering. However, we see the same mistakes often repeated again and over.

Improvements to the bushings

Bushing improvements are needed so what's involved?

Bushings, which are rubber mounts, allow the Impreza WRX Gen4's suspension components to be fixed to the car's chassis. The rubber ones will lose their shape as they age.

By replacing new OEM rubber bushings, you may greatly improve your vehicle's performance.

Because the polyurethane bushes are firmer, the ride may be a bit more harsh, but they will last longer and maintain the handling.

Increased vibration and play may also lead to an increase in the decay in other suspension parts.

A new set of polyeyurothane bushings should assist in mitigate the excessive play associated with rubber bushings.

You may struggle to find a full set of poly bushings, but most stores have the primary mounts available. Often, custom Impreza WRX Gen4 poly bushes may be manufactured to your requirements.

A frequent misconception is that the best setup would be a non-adjustable suspension system that lowers the vehicle by 50mm purchased from a franchised component shop.

Vendors may assert that their Impreza WRX Gen4 suspension kits are compatible with any or all of the Impreza WRX Gen4 model years.

For a vast variety of vehicles, a 'generic one set for all models' approach is obviously incorrect.

How low should you go on the Impreza WRX Gen4?

When it comes to road vehicles, the maximum suspension drop is 26 - 41 mm, but when it comes to versions that come with lowered suspension already, the maximum suspension drop is 21 mm, according to TorqueCars.

Tolerances may be greatly reduced by altering the diameter of the wheels. Lowering a vehicle, even with 17-inch wheels and stock suspension, will create several complications.

Impreza WRX Gen4 Camshaft Upgrades

Getting a fast road cam will helps you to boost top end power which makes it a best mod for NASP and turbo petrol engines, but not so much on diesels. In most cases you will see top end power benefits through performance camshafts on most engines

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large power band gains are on offer for camshaft upgrades.

Fast road cams tend to push up the performance over the rpm range, you might lose a little low end bhp but higher rpm power will be lifted.

Motorsport and race cams, push up the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

On a car driven daily you'll need to optimize your power band to your usage of the car.

I'd be amazed if you have found a Impreza WRX Gen4 Motorsport and race camshaft is at all pleasant when driving around busy urban areas. This is because the lumpy idle will make the car more likely to stall and smooth driving at low rpm becomes impossible. If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be.

Each engine responds differently due to the head and flow characteristics when cams are fitted depending on the cam being less aggressive cam durations so view each engine and camshaft as unique due to manufacturing tolerances and quality variations so check your engine on a rolling road.

The ecu map and fuel delivery and fuel pump also have an effect on the torque gains you'll hit.

Extending exhaust or intake durations can adjust the torque range, and on most engines there are some advantages to extending the intake or exhaust durations and valve lift.

The Impreza WRX Gen4 power plant are great to work on and we note that there is a lot of mods and performance parts about.

ECU Mapping Improvements for the Impreza WRX Gen4

Remaps helps release the full potential of all the parts you've installed on your Impreza WRX Gen4.

Chip Tuning
Another effective way to quickly enhance the performance of your fourth-generation Subaru Impreza vehicles is chip tuning.

Several companies offer their services and promise extended warranties so you can get the most output from your car and still have peace of mind.

One such company is GAN Tuning which offers an impressive gain of 18 hp and 24 Nm through its two different options which are:

  • GAN GA;
  • GAN GA+.

The latter allows the drivers to choose from three different driving modes. This shows the level of command that such systems offer to the vehicle owners.

The best part of the chip tuning process is that despite an imposing increase in both torque and power, the companies offering these services promise improved fuel efficiency.

This makes it an ideal situation for vehicle owners who don’t just get more performance from their cars but also have to spend lesser fuel.

If you are looking for chip modules, you can choose from one of the following manufacturers:

  • SmartTune;
  • JDM;
  • GTE;
  • PIVOT.

These are very cost-effective parts and the freedom they offer is immense. Thus, we suggest that if you want to get the most from your car, try one of these and we’re sure that you’ll be surprised by the outcome.

Air Flow improvements on the Impreza WRX Gen4

It is the main goal to any tuning job to force air and fuel into the Impreza WRX Gen4 engine

Your intake manifold will channel the air from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

The size of bore and shape and flow rate of the Intake manifolds can make a large change to fuel atomisation on the Impreza WRX Gen4.

It's not uncommon that inlet manifolds are needing aftermarket parts, although a few OEM provide fairly well optimized intake manifolds.

Larger Impreza WRX Gen4 valves, doing some port matching and head flowing will also improve torque, the fantastic side effect is it will give you an improved torque increase on other parts.

Impreza WRX Gen4 Turbo upgrades

NA (naturally aspirated) 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 Impreza WRX Gen4

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.

When your motor is fitted with a turbocharger upgrades are going to net you a larger power gain and most turbo charged engines will have stronger components.

There are weak spots for every engine, with some being very over engineered and some only just able to handle stock power. Discover these limitations and install higher quality crank and pistons to utilize the power.

It's not unheard of guys spending loads on turbo upgrades on the Impreza WRX Gen4 only to watch the car throw a rod just after it's been completed.

Large upgraded turbo units will usually experience a bottom end lag, and smaller turbo units spool up more quickly but don't have the top end engines power gains.

In the last 10 years the world of turbo units is always increasing and we commonly find variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo units divert the exhaust flow into 2 channels and push these at differently profiled vanes in the turbo charger. They also help the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor AFM/MAF on the Impreza WRX Gen4 when loads more air is being sucked into the engine.

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

Adding a supercharger or additional turbo will make large bhp gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.


The next upgrade that you should get after adding an air intake system to your car is an intercooler.

What an intercooler does is that it provides continuous cold air to the car’s engine. This air is vital because cold air is denser which means that the oxygen content in it is higher.

The higher the amount of oxygen in the air, the higher the rate of combustion.

This means that by providing cold air to the car’s engine, you increase the power produced by the vehicle.

Some of the companies that offer an intercooler setup for your Subaru Impreza 4th generation car include:

  • COBB;
  • GrimmSpeed;
  • Perrin;
  • Mishimoto.


After a vehicle has started producing more power than what the company had designed it for, the most common issue faced by racing enthusiasts is related to overheating.

This is because when the increased combustion rate produces more heat, the stock cooling system of the car fails to dissipate it.

When this happens, the vehicle’s parts start getting affected and the valves in particular start leaking.

A car’s radiator is a key component of the entire cooling system. That’s because it allows water and air to cool down the temperature of the engine by ensuring that cold water constantly keeps flowing.

Thus, if you want to upgrade the radiator of your Subaru Impreza 4th generation vehicle, here are a few options that you have in this regard:

  • Mishimoto;
  • Koyo;
  • Skunk2.

These are reasonably pricey parts, but after spending so much money on your car's air intake and intercooler, we recommend that you pay attention to the radiator as well.
Otherwise, the vehicle will be unable to provide optimal performance for extended periods of time.

Impreza WRX Gen4 Fuelling Upgrades

You will need to ensure that the engine is not starved of fuel so must increase the fuelling when you start extending past 20% of a performance increase. Fuel pressure boost valves raise the fuel pressure, can improve throttle response.It is important to over specify your injectors flow rate.

As a rule of thumb add another 20% when fitting an injector, this allows for injector deterioration and gives a bit of spare capacity should the engine need more fuel.

Now that your vehicle has a great air intake system, an intercooler, a proper cooling system and even a performance exhaust, the next thing that you will have to ensure is that the fuel delivery to the engine is optimal.

While stock parts do well for unmodified vehicles, their performance often falls short when we head over to the modified section.

That’s because most car manufacturers design their vehicles to be as fuel efficient as possible. The preferences of performance car enthusiasts are however different.

As they want to get the most out of their cars, they have to install an aftermarket fuel delivery system.

Some of the fuel delivery-related parts that most vehicle owners change on their vehicles include but are not limited to:

High-Pressure Fuel Pump;

Fuel Pressure Regulator;

Injector Driver;

Fuel Injectors.

High-Pressure Fuel Pump

For this part, you have the following manufacturer options:

  • Walbro;
  • BOSCH;
  • DeatschWerks.

Fuel Pressure Regulator

The fuel pressure regulator is offered for the Subaru Impreza 4th generation vehicles by many companies, some of them include:

  • Hybrid Racing;
  • Perrin;
  • DeatschWerks;
  • BLOX;
  • AEM.

Injector Driver

We recommend getting Hondata’s injector driver for your vehicle. While it is an expensive part, its high performance justifies the price.

Fuel Injectors

Another part that has a lot to do with the proper fuel delivery to the engine of your Subaru Impreza 4th generation vehicle is the fuel injectors.

TLF Performance Parts offers aftermarket fuel injectors for this vehicle and you can choose them to get the desired output.

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.


A fast-moving car also requires an effective braking system. That’s because if the vehicle can’t be controlled at high speeds, there is no point in taking it to its limits.

Brake upgrades may not dramatically shorten stopping distances but it will resist fade for longer and perform effectively under more extreme conditions. 

Tuned cars are generally driven harder and are often used on track days so upgrading the brakes makes a lot of sense, but which areas should you focus on?

The following braking-related parts are usually upgraded on the fourth-generation Subaru Impreza vehicles.

  • Brake Pads - higher friction and heat resistant coatings;
  • Brake Rotors or discs - vented grooved and drilled & Larger surface area.
  • Callipers (adding more pots or larger callipers to house bigger pads)

Brake Pads

These are the most important part of a braking system and thus we recommend that you choose the ones from a good manufacturer. You have the following options in this regard:

  • Hawk;
  • Power Stop;
  • EBC;
  • R1 Concepts.

Brake Rotors

Although they cost a lot of money, brake rotors are one of the most upgraded performance parts. Here are some of the companies that offer brake rotors for the Subaru Impreza 4th generation vehicles:

R1 Concepts;

Power Stop;

Stop Tech.

Impreza WRX Gen4 Performance Exhausts

You only need to to increase your exhaust if your current exhaust is creating a flow problem.

On most factory exhausts you'll see your 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.

Sports exhausts equal out the flow of air through the engine.

Most people believe that the purpose of the vehicle’s exhaust is just to expel the hot gases out of the car, they are unaware of the fact that the exhaust system of a car has a lot to do with the overall output of the vehicle.

The main function of the exhaust system indeed is to get rid of the hot gases ASAP to keep the engine cool. However, another important function that these systems perform is that they provide an aggressive sound to your vehicle.

Well, what good is a modified vehicle if it doesn’t have a roar? So, if you want to convert your 4th generation Subaru Impreza into a head turner, getting an aftermarket performance exhaust system is your best bet.

The following companies offer exhaust systems for these vehicles:

  • Takeda;
  • HKS;
  • AVO Turbo.

Common exhaust restrictions are traced to the emissions filters installed, so adding a higher flowing performance aftermarket catalyst removes the restriction, and rather than doing an illegal catless mod, will keep the car road legal.

We should explain that performance catalysts and filters perform a similar power improvement to cat removal and have the added benefit of keeping your car street legal, as decat or catalyst removal is not a legal mod.

Alloy Wheels

When you have installed a number of performance modifications on your vehicle, you would definitely want it to stand out from the crowd.

Wheels play a great role in giving your vehicle an entirely new and unique look.

You can use the great wheels from the Enkei and SSR range for your Subaru Impreza 4th generation vehicle. Let us know in the comments which brands you've used and how it went for you.

Weak spots, Issues & problem areas on the Impreza WRX Gen4

The Impreza WRX Gen4 engines are generally reliable and solid as long as they are well maintained.

Carbon build up in the head, particularly around the valves which will cause flat spots and loss of power, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon To minimize this risk only use quality fuel and don't short journeys.

Service time oil changes are essential on the Impreza WRX Gen4, especially when tuned and will help ensure reliability of the engine.

If you want to know more, or just get feedback on Tuning your Impreza WRX Gen4 engine please join us in our friendly forum where you can discuss Impreza WRX Gen4 tuning options in more detail with our Impreza WRX Gen4 owners. It would also be worth reading our unbiased Subaru tuning articles to get insights into each modification and how effective they will be.

Please help us improve these tips by sending us your feedback in the comments box below.

We appreciate people taking the time to tell us what our members have got up to and which upgrades work best for them on each model of car. We use your comments and feedback to improve the accuracy of these Impreza WRX Gen4 tuning guides which get regular updates and revisions.

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