So you've had your 2015+ Subaru WRX for a while now and your warranty is almost over. You want to start modifying your WRX but you don't know what you need. Where do you start? In this article, we’ll cover and go into details on the must have modifications to increase HP for your WRX.


In 2015, Subaru ditched the old EJ engines used in their previous generation WRX’s. The 2015+ Subaru WRX introduces the brand new engine called the FA20DIT. If the name FA20 sounds familiar to you, that is because it is the same engine used in the Scion FRS and Subaru BRZ. However, the FA20DIT comes turbocharged from the factory producing 268 HP while the naturally aspirated FA20 only puts out 200 HP. It wasn’t long until people have started modifying their WRX and figured out which parts are proven to work.




Cobb Accessport 

A Cobb Accessport should be the first thing on your checklist when modifying your Subaru. It is needed to be able to tune the car. It is truly the key to unlocking the untapped power in your WRX. Not only that, it allows you to switch between different map settings, adjust your launch control as well as the ability to monitor 6 gauges, and troubleshoot ECM related trouble codes.


Cobb Flex Fuel Kit & DW300 Fuel Pump

For those who have Flex Fuel available (otherwise known as Ethanol or E85), the Cobb Flex Fuel Kit is the best "bang for buck" modification available for the FA20DIT. Being that this engine is Direct Injection, it responds VERY well to an E60 mix. Ethanol has a much greater resistance to Pre-Ignition Detonation, or PING for short. If you are going this route, you will also need a Deatschwerks DW300c as the OEM in-tank Low Pressure Fuel Pump (LPFP) is not E85 compatible and will fail over time. Another great option compared this pump would be the AEM340 with the DW install kit which includes the fuel filter sock.


Grimmspeed Catted J-Pipe 

One way to increasing the HP output is to open-up the breathing room of the exhaust system. The OEM J-Pipe uses a smaller diameter tubing than most aftermarket J-Pipes and contains highly restrictive catalytic converters. This is where an aftermarket J-Pipe comes into play. 

The Grimmspeed Catted J-Pipe is one of the best performing J-Pipe currently on the market. Grimmspeed has put many hours behind research & development to perfect every detail. What you get is a one piece Catted J-Pipe that uses an innovative 1/2" flange design to give a smooth 3” to 3.5” transition with a high flow, 300 cell metallic catalytic converter.

Another high quality catted J-Pipe option would be the Invidia Catted J-Pipe. Invidia is also a top notch brand fabricated in Australia. 


GrimmSpeed Top Mount Intercooler + Charge Pipe

A Top Mount Intercooler upgrade on the 2015+ WRX goes hand in hand with a J-Pipe. It allows you to keep the charged air going into the engine at a consistent temperature. High intake manifold temperatures will cause pre-ignition detonation or otherwise known as "knock". Once again GrimmSpeed has given us one of the most reliable TMIC upgrades on the market for the 2015+ WRX. The Grimmspeed Top Mount Intercooler has the highest efficiency of any TMIC on the market. It also includes the ducting to meet with the hood to maximize the use of the hood scoop. To fully utilize the potential of this intercooler, we also recommend pairing GrimmSpeed's Charge Pipe upgrade.


ETS Front Mount Intercooler Kit



A Front Mount Intercooler is recommended for enthusiasts looking for maximum charge-air cooling and aggressive street/track setups. The bigger core and piping combined with the location ensure that your WRX will remain "knock" free during aggressive driving as well as high ambient temperatures. The engine produces very high temperatures when in high RPM for extended periods of time. The ETS Front Mount Intercooler upgrade is the top choice on the consumer and competitive market. ETS backs all of their product with research and testing and they have not let us down with this kit. This kit is available in 3", 3.5" and 4" core thickness.


IBR 1 Piece TGV Delete + EGR Delete

The TGV/EGR Delete combo is one of the best $$/HP gain when combined with an accommodating tune. The 1 Piece TGV Delete provides the maximum, unrestricted air flow between the intake manifold and the intake ports of the cylinder head. The EGR Delete will be one of the best thing you can do for the health of your engine. This eliminates the recirculation of exhaust gasses back into the intake manifold. The EGR system is a factory piece of equipment designed to reduce emissions. This unfortunately leads to very high intake manifold temps as well as non-ideal air mixture for maximum power output. 


GrimmSpeed 3 Port Electronic Boost Control Solenoid

The GrimmSpeed 3 Port Electronic Boost Control Solenoid (EBCS) allows for much greater boost control over the OEM 2 port boost controller. This EBCS separates 1 shared port into 2 separately controlled ports. This allows for very accurate tuning capabilities. It enables your tuner to give you the most out of your tune as safely as possible.


ETS Air Intake or GrimmSpeed Stealthbox Intake

Grimmspeed StealthBox                           

Grimmspeed Stealthbox Intake - 2015+ Subaru WRX

ETS Intake W/ Heatshield

ETS Intake - 2015+ Subaru WRX


Once reaching certain power levels, the OEM intake and airbox will become another bottle neck. An aftermarket intake that is beneficial has larger diameter tubing, high-flow filter and a well insulated air-box. Both the GrimmSpeed StealthBox and the ETS Intake w/ Heatshield + Air-Box have stepped up to the plate and knock it out of the park. Both of these intakes will provide true airflow gains while isolating your intake from the high temperatures of the engine bay. It is not recommended to install an intake without a box or heat shield. 


Killer B Air/Oil Separator (AOS)

In any turbo charged application, there are higher amounts of crank case oil gases produced. Installing the Killer B AOS on your 2015+ WRX will keep all your intercooler and piping clean of oil residues ensuring the cleanest of air is entering your engine at all times. The main tank assembly is baffled inside, giving as much surface area as possible for oil vapor to be collected. An advantage to to AOS over catch cans is that they are heated by coolant. This means no draining the catch can regularly or worrying about it freezing during the cold months. If Killer B is unavailable, other great options include IAG, Crawford and Perrin. 



Killer B Headers w/ Dual External WasteGates 

This Killer B Headers w/ Dual External Wastegate would be one of the final pieces of the puzzle for those wanting the most out of the FA20DIT. Made with the highest of quality, being constructed of 321 Stainless Steel. When combined with Dual External Wastegates (EWG) superior control of boost levels is gained. Exhaust gas potential is used to the fullest with this set up. External wastegates also allow for a Catless J-Pipe to be used safely with the possibility of boost creep eliminated. This header also utilizes the FA20DIT twin scroll design to be combined with the OEM or larger aftermarket turbo options, like the Forced Performance FP Blue which we also recommend if you're after 400+ WHP. 


Boomba Racing By-Pass Valve (BPV) 

The Boomba Racing By-Pass Valve is an exceptional way of upgrading the OEM BPV while still keeping the system fully recirculating. It has been designed and tested to withstand much greater pressures than the factory equipped BPV. In turn, it can be incorporated into a build involving any size turbo application. When paired with an intake, it can be heard between shifts during aggressive driving.


Forced Performance FP Blue

Forced Performance has been a top contender for turbo upgrades on all previous generation WRX/STI with the EJ platform.  Many options like the FP Red, Blue, Black and even Blue have all been offered, but only for EJ based vehicles. The new FP Blue for the 2015+ WRX is a 73mm, twin scroll turbo available in Journal Bearing or Ball Bearing construction depending on intended application. A huge advantage to this turbo is fact that it retains the twin scroll design of the FA20DIT. This keeps your power band more linear rather than waiting for your larger turbo to "spool".


IBR BRZ Intake Manifold Kit

So at this point, you've probably maxed out your FA20DIT due to certain restrictions that are outside of your control ie, fueling and total air flow. If you have an ETS or PRL FMIC, the IBuildRacecars BRZ Manifold Swap Kit would be hands down the next direction you should go in. The BRZ intake manifold has been tested and proven to provide greater airflow between the manifold runners and cylinder heads. The gains you and your tuner will achieve will be noticeable and are obtained by simply increasing air flow. This kit accommodates a FMIC by utilizing the WRX throttle body bolted onto a forward facing BRZ intake manifold. There is also a cold side pipe needed offered by ETS or PRL. Custom piping is also a great alternative. To allow the manifold to be bolted to the WRX cylinder heads, an adapter is included that also acts as a 1 Piece TGV Delete similar to the parts mentioned earlier. This also leaves the door open for adding a set of port fuel injectors once some ground is made in the tuning world. 

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