2015-2021 Subaru WRX cars under the VA chassis code are equipped with the FA20F engine. The FA20F, also commonly referred to as the FA20DIT, is a direct injected 2.0L flat-four twin-scroll turbo engine. Producing 268hp and 258lb-ft. of torque, the small engine outputs a decent amount of power for its size.
However, the WRX is often overshadowed by its bigger brother, the WRX STI. The STI is powered by the larger EJ257 engine, a 2.5L turbocharged flat-four with sequential multiport fuel injection. The STI and its EJ257 engine produce 300-310hp and 290-300lb-ft. of torque in the base models.
Fortunately, the WRX and the FA20DIT engine can easily produce 300+whp with a few simple bolt-on modifications. This guide will cover the 6 best WRX mods and show you how these simple bolt-on upgrades can add up to 100whp of power gains.
Subaru WRX FA20F Power Limits
Before we dive into the best mods, we need to discuss power limits. One big downside of the WRX is that the FA20DIT has weak connecting rods. Too much low-end torque tends to be the cause of connecting rod failure on the WRX. 325-350lb-ft. of torque is when connecting rod failure becomes a concern. With respect to horsepower levels, the rods commonly fail within the 320-350whp range.
Piston failure is also common along with connecting rod failure. Rod and piston failures also usually take the whole engine out with them, requiring a new engine. These WRX internal engine problems put a damper into performance potential. If you are looking to make 350+whp then we recommend upgrading your internals. However, failure at levels even as low as 300whp aren’t uncommon so keep this in mind as you mod your WRX.
The key to preventing FA20DIT rod failure is to keep boost low and run a conservative tune. Don’t push the boost above 22psi and use a tune that limits low-end torque.
With all this being said, BrenTuni
ng did push 452whp and 414wtq (mustang dyno) on a completely stock engine and turbo. They claim the engine was pushing over 380whp for over a year with zero issue. So, the FA20DIT does have a bit more power potential in it than we claim above. The key to hitting power levels like these while maintaining reliability is all in the tuning. And some luck.
Best WRX 2.0L Turbo Mods
- J-Pipe / Downpipe (recommended new EBCS)
- EGR & TGV Delete
- E85 Fueling
Recommended Supporting Mods
- Electronic Boost Control Solenoid (EBCS)
- Chargepipe & BOV
All of the mods listed here will get you in the 340-350whp and 350-360wtq range. Without E85 fueling you will probably be around the 320whp and 330wtq mark. A stock WRX will dyno in the 220-230whp and 240-250wtq range. This means you have about 100whp of play before you start entering dangerous territory for the FA20DIT connecting rods.
1. FA20 WRX Flash Tune
The stock factory tune on the WRX isn’t great. It’s aggressive on boost, has a lot of rev hang, runs lean, and overall isn’t very friendly to performance mods. While the tune is completely fine for the stock engine in our opinion, a lot of performance improvements can be had by adjusting it.
A flash tuning device is first on our list since it offers the best bang-for-the-buck and is the best place to start. Outside of fixing the factory tune’s imperfections, it offers the largest power gains out of any mod on this list. Tunes adjust fueling, boost targets, engine timing, and numerous other variables to improve power and overall performance.
While the flash tuners we list below all offer off-the-shelf tunes, we highly recommend custom tuning for anyone looking to push more than 300whp. As mentioned earlier these engines are a bit more delicate and can only handle so much low-end torque. Getting a custom tune from a tuner who understands the weaknesses of the FA20DIT is important for improved reliability.
Lastly, the benefits of all the other mods on our list are improved with a tune. When a tune is combined with an intake, j-pipe, etc. the power gains from the intake and other mods increase.
WRX Flash Tune Benefits
- 20-60whp gains and similar torque gains
- Improved power curve
- Reduced rev hang
- Smoother performance
Best 2015+ Subaru WRX Tune
- Cobb Accessport
Cobb is one of the most trusted names in tuning software. Additionally, it is one of the only providers for the WRX outside of EcuTek which is a more advanced tuning software and not a plug-and-play system. The majority of the custom tuners on the market, such as BrenTuning, custom tune off of the Cobb Accessport.
2. FA20DIT Upgraded Intake
A performance intake system is an important upgrade once you add a tune to the WRX. Increasing boost levels and creating more power requires more airflow. Once you add a tune and turn up the boost on the FA20, the stock intake system becomes restrictive. Without enough airflow, the turbocharger quickly becomes overworked trying to compress the air to higher boost levels.
An upgraded intake will increase air flow by 40%+ over the stock intake, allowing the turbocharger to work more efficiently. While an upgraded intake will only add maybe 5whp on a completely stock engine, when you combine it with a tune the gains can increase to around 10whp.
Open Air & Closed Box Intakes
Cold air intakes usually come in two designs: open air or closed box. Open air intakes have the filter directly exposed to the engine bay. Most will use a heat shield to try to block some hot engine air from being sucked into the intake system. Closed box intakes have the air filter completely enclosed within a box to prevent the intake from sucking in hot engine bay air.
Open air systems will provide greater airflow increases since there isn’t a box creating restriction. Closed box systems will flow less air but have very slightly lower intake air temps (IATs) since the filter isn’t exposed to the engine bay air.
People will tell you that you need a heat shield at the least and that enclosed systems are better because of lower IATs. While most intakes do at least use heat shields, you honestly don’t need one. Intake air temps really don’t matter that much on intercooled engines like the FA20DIT. Air that enters the intake gets sent to the turbocharger. Turbochargers run very heat which causes the air temps to increase anyways. The air is then sent through an intercooler to be cooled down before entering the engine. Initial IATs don’t impact the intercoolers ability to adequately cool the charge air.
We recommend open systems since the increased air flow is more important than the slightly colder IATs. However, unless you are upgrading your turbo a closed box cold air intake will work just as well as an open intake.
J-Pipe EBCS Upgrade
We are going to cover this in more detail in our supporting mods section below. EBCS is the electronic boost control solenoid which controls the amount of boost that is sent to wastegate. The FA20DIT has a poorly designed EBCS from the factory which causes a lot of boost spikes.
Again, we’ll cover this more below. But when you upgrade your J-pipe it is highly recommended to upgrade your boost control solenoid to a 3-port EBCS.
WRX Upgraded Intake Benefits
- 5-10whp gains and similar torque gains
- 40%+ increases to airflow
- Improved turbo efficiency
- Cool intake ‘whoosh‘ sound
Best Upgraded WRX Intake Systems
3. WRX J-Pipe / Downpipe Upgrade
Behind a tune, the second larger power gainer is an upgraded J-Pipe. Now that we have a tune and are bringing extra air into the engine with the intake, we need to reduce the restriction within the exhaust system. More air flowing in means more air to flow out. The stock J-pipe, also called a downpipe, bolts up directly to the turbo and houses the primary catalytic converter.
Since the j-pipe/downpipe holds the catalytic converter, it is restrictive. And since this restriction is so close to the turbo it impacts performance. With a tune and intake, the j-pipe is going to create a lot of post-turbo pressure. Post-turbo pressure impacts the turbos ability to spool quickly and therefore impacts power and performance. Less backpressure also creates lower exhaust gas temps while reducing stress on the turbo which overall creates a more reliable engine.
We aren’t going to cover cat-back exhaust upgrades here since the small power gains don’t justify the cost in our mind. Unless you just want the louder exhaust sound. The downpipe is the most restrictive part of the exhaust system and therefore is the most important exhaust upgrade.
Catted vs. Catless J-Pipes / Downpipes
Since the J-pipe houses the cat, you have two options. Upgrade the cat to a high-flow cat or completely remove it with a catless downpipe. High-flow cats are legal and will pass emissions in most states, but they are also more restrictive than catless options.
You won’t pass emissions with a catless j-pipe and it is technically illegal. But you get the biggest power gains and the least exhaust restriction. Catless downpipes will probably offer about 5whp more than high-flow options.
With all that being said, unless you are aggressively tracking your car or shooting for 400whp+ levels then a high flow catted J-pipe is going to be completely adequate. While we love the performance benefits of catless options, we recommend sticking with a high-flow catted J-pipe for the sake of being above the law.
WRX FA20DIT J-Pipe Upgrade Benefits
- 5-15whp gains
- 10-20whp gains
- Faster turbo spool (less turbo lag)
- Slightly louder exhaust note
- Less exhaust backpressure
- Lower EGTs
Best WRX J-Pipes
4. FA20DIT WRX Intercooler Upgrades
A stock FA20DIT engine has a top mount intercooler (TMIC) instead of a more traditional front mount intercooler (FMIC). The benefit of a TMIC intercooler is that it is a lot closer to the engine meaning there is less piping for the air to travel through, reducing turbo lag. FMIC’s are larger and therefore have more cooling capacity and also do a better job at reducing heat soak. However, the long tubing required creates a lot more turbo lag.
When you upgrade the cooling system on a FA20DIT WRX you can either upgrade the TMIC or swap the TMIC out for an FMIC. Changing to an FMIC is usually only recommended for heavily tracked cars or cars running very aggressive setups with an upgraded turbo pushing 400whp or more. Therefore, for the average mod enthusiast just looking for some bolt-on power we recommend sticking with an upgraded TMIC. Adding a front mount also requires a lot of cutting and modifications to the front bumper to get it to fit.
The OEM top mount intercooler is notorious for heat soak. While an upgraded intercooler won’t provide a ton of additional power gains it will provide more consistent power and prevent power loss caused by heat soak. Heat soak can cause pre-detonation and engine knock. Outside of an intercooler providing better performance it is also a good reliability mod as it keeps engine temps cooler and more consistent.
WRX Top Mount Intercooler Upgrade Benefits
- xxx power gains
- Lower intake air temps
- Less heat soak
- More consistent power
Best FA20DIT Upgraded TMIC
5. WRX EGR & TGV Delete
Subaru’s TGV system is the tumble generator valve. It is essentially a butterfly valve that sits inside of the intake runners and controls airflow. At low RPMs the TGV restricts airflow to allow for cleaner emissions. The valve fully opens at high rpms, however the flaps and springs inside of them take space and restrict airflow.
A TGV delete kit removes the valve plates (flaps), springs, etc. and instead uses a simple hollow design that has zero airflow restriction.
EGR is exhaust gas recirculation. EGR valves recirculate exhaust gas back into the intake system to burn any unburnt fuel after combustion. The problem with EGR systems is that they cause a ton of carbon buildup in WRX’s which affects performance and also alters the density of air entering the combustion chamber.
Deleting the EGR system removes the recirculation valves and tubing and plugs the ports. Because it reduces carbon buildup it improves airflow and it also improves the density and cleanliness of air entering the combustion chamber, increase performance.
Deleting either or both of these items will require a custom tune.
A TGV delete is more of a performance mod whereas an EGR delete is more of a reliability mod. Disclaimer: since both of these systems are emissions related deleting them is technically illegal.
WRX TGV & EGR Delete Benefits
- About 10whp and similar torque gains
- Eliminates carbon buildup
- Improves air flow
- Lower intake manifold temps
6. WRX FA20 E85 Fueling
If you want to reach 350whp, you likely aren’t going to be able to do it without running ethanol, E85 fuel. E85 fuel has an octane rating of 108 and burns a lot cooler and cleaner than pump gas, This allows for more aggressive ignition timing and more boost.
However, E85 has a lower energy content compared to gasoline. It also burns faster because it vaporizes more quickly. This matters because it requires more ethanol to be injected into the combustion chamber compared to gasoline. The stock WRX low-pressure fuel pump doesn’t flow enough fuel to be able to run 100% E85. Therefore, to run 100% E85 you need to upgrade the LPFP. Additionally, running any amount of E85 will require an E85 calibrated tune.
The stock LPFP can however handle about 30% E85, also called a blend. Running E30 you can expect to get about 10-15whp gains. If you plan on upgrading the LPFP and running higher blends, or 100% E85 you can see power gains up to 30-40whp.
WRX Flex Fuel Kit
E85 requires custom tuning. If you aren’t running 100% E85 you will need a flex fuel kit (Cobb has a good one) that accurately measures E85 fuel content. Pump gas has some ethanol in it and the amount of ethanol in it varies. Without a flex fuel kit you won’t be able to accurately measure what mix of E85 to gasoline you are running and would essentially have to retune the car every time you fill up. The flex fuel kit allows you to seamlessly switch back and forth between E85 and gasoline, and different blends of each without more tuning required.
Most people recommend running an E50 or E60 blend. Running full E85 is possible with an upgraded LPFP, but do to the lack of lubricity this will likely take out the HPFP at some point, requiring that to be upgraded as well.
One downside to E85 is decreased gas mileage since it requires more fuel to be burned. However, the lower cost of ethanol fuel mostly offsets this.
WRX E85 Performance Benefits
- 10-40whp gains and similar torque gains
- Reduces chances of knock or predetonation
- Burns cooler, benefiting engine temps
WRX 300whp+ Supporting Mods
There are two mods in specific that we highly recommend for anyone following the mods on this guide. The first is an upgraded EBCS which we touched on briefly earlier. The second is an air/oil separator.
1. WRX Electronic Boost Control Solenoid Upgrade
An EBCS upgrade is recommended for anyone who is running an upgraded J-pipe or downpipe. The EBCS diverts boost pressure to the wastegate. The stock solenoid on the FA20DIT is a 2-port solenoid. This essentially splits boost between the wastegate and the turbo and is inaccurate and causes lots of boost fluctuations.
The factory EBCS is not compatible with upgraded J-pipes due to the decreased amount of backpressure. The decreased backpressure results in the turbine wheel spinning more freely and with less restriction against it. Because the stock 2-port EBCS is inaccurate and slow at adjusting it causes even worse boost fluctuations.
Without getting into the details, a 3-port boost control solenoid solves all of the issues. It allows the engine to hold boost better, eliminates boost fluctuations, and reduces stress on the turbo.
You can run the stock boost control solenoid with an upgraded j-pipe but we do not recommend it due to the crazy boost fluctuations you’ll get which isn’t safe for the turbo or engine. Cobb and Grimmspeed both offer great upgrade options.
2. FA20DIT Chargepipe & BOV Upgrades
A chargepipe routes the air from the intercooler to the intake manifold. Because it is after the turbo it carries highly pressurized “charge air”.
The FA20DIT chargepipe is made of plastic. Well, very high pressure and plastic don’t go too well together. While the chargepipe isn’t an issue on a stock FA20 WRX, once you tune it and increase the boost levels it becomes prone to breaking. The high pressure causes the chargepipe to crack or completely pop-off of the intercooler. When the chargepipe goes it will leave you stranded on the side of the road.
The chargepipe is actually also restrictive. So, upgrading it does have some performance benefits, albeit nothing extremely material. So upgrading your chargepipe is not only a great reliability mod but also provides some performance benefits as well.
When you upgrade your chargepipe you also have the option to replace the stock blow-off valve. The stock BOV is known to leak boost a bit under high boost levels. It also adds a cool “psh” sound whenever boost is released.
Overall, upgrading your chargepipe is highly recommended once you are over the 300whp mark.
Subaru WRX FA20DIT Performance Mods Summary
Getting an extra 100whp out of your 2.0L Turbo WRX is possible with a handful of rather inexpensive bolt-on modifications. However, the biggest downside to tuning the FA20 WRX is its weak connecting rods. While there are a handful of individuals who have pushed past these levels, 350whp and 350wtq seems to be about the absolute maximum before the connecting rods fail. Reliability appears to deteriorate rather quickly once you breach the ~300whp/wtq thresholds.
Anyways, a full-bolt on WRX with a tune, intake, j-pipe, and intercooler will land you around 320whp. That’s a gain of nearly 100whp over the stock FA20DIT for less than $3,000. With a bit of extra cash thrown into a flex fuel kit, upgraded LPFP, and custom tune you can exceed 350whp.
Toss in some aggressive tuning, a full exhaust system including headers, a front mount intercooler, and upgraded clutch and the stock engine and stock turbo can produce approx. 450whp. Granted the stock engine won’t last very long at these levels, the stock turbo at least seems to be quite capable.
We recommend upgrading your internals above 350whp and upgrading your turbo for any power goals in excess of 400whp. Once you eclipse 400whp you will also want to swap the top mount intercooler for a front mount option.
What has your experience been with tuning and modifying the 2.0L Turbo WRX FA20DIT?