The WRX STI is a true Japanese classic. From its classic grandma-pissing rumble that everyone loves to the ability to bring a whole family of vapers together. The EJ platform has been around kickin' a$$ and taking names for a the past few decades. Whether your intentions are to have a sick daily whip or a fully dedicated track beast; the WRX STI has you covered. To achieve the power and reliability that you desire, here is our Subaru STI parts recommendations.
Killer B Ultimate Oil Pickup + Windage Tray
AEM 320 Fuel Pumpe
Injector Dynamics ID1050X Fuel Injectors
Cobb Flex Fuel Sensor Kit
Grimmspeed Electronic Boost Control Solenoid
Grimmspeed Catted Downpipe or Invidia Catted Downpipe
Torque Solution Air Pump Delete
Torque Solution TGV Deletes
ETS Top Mount or Front Mount Intercooler Kit
ETS Cold Air Intake
Perrin Turbo Inlet
Perrin Equal Length Big Tube Headers
Grimmspeed EWG Up-Pipe
Radium Dual Catch Cans
The Killer B Ultimate Oil Pickup paired with the Oil Baffle Windage Tray has been engineered to prevent oil starvation, especially during spirited driving. The OEM pickup has been known to crack over time due to poor factory design. This will lead to premature engine failure and reliability is not something you want to worry about. The Windage Tray prevent oil from sloshing around in the oil pan during hard shifting and cornering. This keeps the pickup surrounded with oil at all times, also reducing oil aeration.
The Cobb Accessport is the tool, or gateway rather to tuning your WRX STI. The the Accessport itself comes with a few Off The Shelf (OTS) maps pre uploaded The main advantage is gaining the ability to having your vehicle protuned. Tuners all around the world tune using this platform as it has been proven to be a a great product, as Cobb has always produced. You can also perform datalogging and view up to 6 gauges at once on the display.
The AEM 320 fuel pump address one of the main weakness of the WRX STI; consistent fueling. The factory fuel pump can simply not provide sufficient fuel pressure with what the STI demands. The AEM fuel pump is also fully compatible with ethanol, allowing you to make the jump to E85 at any time. This part paired with the ID1050x injectors will ensure your STI has all the fuel it will need.
The ID1050x is the newly improved ID1000 and part of the X Series line up. This injector paired with the AEM 320 will allow you to run higher boost levels while maintaining reliability. Consistent fueling through the power band is extremely important as too lean of a mixture can cause catastrophic engine failure. Keeping your Air-Fuel Ratio (AFR) at the correct levels is key to preventing Pre Ignition Detonation (PING) or knocks from occuring.
The safest and quickest route to making power on any turbo vehicle is usually Ethanol or better known as Flex Fuel. The Cobb Flex Fuel Sensor Kit allows you to have the appropriate sensor to measure your ethanol content accurately. This is also a monitor on your Accessport once you have this installed. Ethanol has a much higher resistance to detonation than gasoline, but it is also consumed much faster. Running flex fuel also requires an accompanying tune and an upgraded in-tank fuel pump. It is also recommended to combine this with the Cobb Fuel Pressure Sensor.
The GrimmSpeed Electronic Boost Control Solenoid is one of the cheapest yet first performance mod you should consider if you are getting a protune. The stock EBCS is only a 2 port whereas the GrimmSpeed is 3 port. The 3 port upgrade allows much more accurate control of boost levels; giving your tuner everything they need to give you the best results.
An OEM Downpipe contains two very restrictive catalytic converters. By replacing the Downpipe with a high flowing aftermarket option is one of the first modifications Subaru owners do to their vehicle once they've purchased an Accessport. By upgrading to either of these great catted choices, you are also ensuring that your vehicle will be safe during situations where boost creep may occur. Boost creep is a mechanical issue that may occur on catless setups without running an External Wastegate. We highly recommend the high-flowing catted Downpipe for this reason. Both the Grimmspeed Catted Downpipe and the Invidia Catted Downpipe offers optimal performance at very similar pricing.
The Second Air Pump system is a factory equipped system designed to pump air into the exhaust to produce better emissions. This component is known to fail and has actually caught on fire in some cases. When modifying your engine, this is usually one of the components to be removed. The Torque Solution Air Pump Delete is machine correctly to fit in place of the air pump and also comes in a black anodized finish.
The Torque Solution Tumbler Generator Valve (TGV) Deletes are a must if building any higher horsepower EJ engines. The OEM TGV resitricts air flow between the manifold and the cylinder heads. Modifying the OEM one is an option but thee fully machine components have polished smooth ports to ensure maximum airflow.
ETS Front Mount or Top Mount Intercooler (FMIC/TMIC)
An intercooler upgrade from ETS will really set your car up to make safer power. ETS has always been a top-quality producing company that the Subaru community can rely on. Whether you choose a FMIC or TMIC really depends on application and your long term goals for the car. Most FBO (Full Bolt On) builds will not outperform the TMIC, especially if the car isn't seeing any track time. If you are shooting for over 400whp and intend to use that power regularly, the FMIC should be your choice. If the car is used on the street in hot climates, TMIC can also suffer from heat soak sitting in traffic.
The stock intake air filter sits in the engine bay which receives a lot of heat coming from the engine. The ETS Cold Air Intake System relocates the cone filter to the inner fender, providing plenty of cool air to keep your manifold temps nice and low. Also available in a variety of finishes. It is advised to upgrade the fuel system when installing an intake and down pipe setup.
The Perrin Turbo Inlet is often one of the first engine mods, especially when paired with the above intake. The silicone material is designed for smoother air flow and also remove the pleats that are found in the stock inlet. Slight throttle response can be observed, but the clean finish it gives in the engine bay certain will not go unnoticed.
It's no secret at this point that the OEM Unequal Length design is poorly designed and holds the car back during the full RPM range. This header from Perrin Performance addresses this issue and also increases piping diameter. This header uses 1.625" primary tubing and 304 stainless steel flanges. You lose some of the renowned "rumble" sound, but the benefit of equal length is a significant power gain at any point in the power band.
The OEM Up-Pipe has been proven to be very restrictive and is common swapped out when moving to a pro tune. Given the opportunity to upgrade the up-pipe, the choice would be to stick with the Internal Waste Gate or move to External Waste Gate. Moving the turbo's waste gate to an external location relieves the turbo of a lot of turbulence, especially if a Divorced Waste Gate Down Pipe is not being used. The benefit is increases boost control while picking up some horsepower has a result. Not to mention the sound of an EWG cannot be compared.
An oil catch can is imperative in preventing crank case oil vapors from recirculating into the cold side of your turbo. This prevents sludge build up in your intercooler, piping, intake throttle body, etc. This results in cleaner charged air entering the inlet, raising overall engine performance and producing cleaner exhaust gases. Be sure to empty the reservoir as part of routine maintenance.