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8 Best STi Mods

Posted by Reid @ Rev Works on 8/1/2016 to Informative

Where to Begin

So, you have a 2008 or later Subaru STi and you’re wondering what your first step should be. While we are mainly known for our top-notch motor builds, we also do a ton of bolt-on modifications for people just getting started with their STi builds. We get tons of questions about what the best route for getting started on one of these cars is, so we decided to come up with a blog post to let people know. We’ve put some thought into it, and put together this list of things we think offer the best performance bang-for-buck when you’re first getting started modding one of these (already) awesome cars.

Getting Some Traction on Your Build

Horsepower and braking are super important to factor into any build, but more important than both of these is traction. If you can’t get the power to the ground, or allow the brakes to get enough grip to stop you, you’ve got serious problems. The best way to improve traction is to go with more aggressive tire compounds and larger section width if warranted (along with all the other nuances of tire selection such as sidewall characteristics, how the tire handles heat, specific considerations for the circumstances the tire will be used in, etc). Many people start their build with lighter, wider wheels that reduce rotating mass as well as the use of wider tires for more traction. Most premium wheels are manufactured using much more expensive machining processes and better metals than OEM wheels which allows them to weigh much less yet perform at a higher level while being *more* durable than OEM wheels in most cases. Couple that with the benefits of better tires (better braking, cornering, acceleration) and you’ve got potentially the single biggest performance increase that you’ll actually *feel* in the entire build process! Many people will be able to shave a few seconds off their lap times at the track just by switching wheels and tires to something a little more aggressive. That’s huge!

Dialing in Your Suspension


The Subaru WRX STi is known for its rally heritage and top-notch suspension setup right from the showroom floor. Subaru engineers really put all of that racing experience to good use in the design process for this car! With that said, car companies have a lot to consider when they design a performance vehicle: Safety, Reliability, Liability, and, of course, Cost. All of these things considered, the suspension we get from the factory with our STi is superb! But for the end-user who wants to get a lot more out of this chassis and really push it to the limit, it’s obligatory to add in some adjustability, better quality components, and some bushings to tighten up the compliance engineered in by Subaru. The most logical place to START on your suspension setup is by getting a good set of coilovers. Aftermarket coilovers allow for a lot more tunability as well as much better quality dampers and springs which will run much smoother much longer than the factory components on a race track or spirited drive. When you get a set of coilovers, it’s often wise to get adjustable arms, sway bars, and bump steer correction to properly tune and align your suspension geometry for maximum effectiveness. The final touch that really sets off your suspension set-up is dialing in your steering feel and driveline rigidity with bushings. Installing aftermarket bushings to tighten up the steering rack, driveline, and chassis makes the car feel *much* tighter, and respond much more quickly to steering inputs. Less body-roll, more responsiveness, and a feeling of agility can all be attributed to aftermarket bushings (especially when coupled with the suspension mods mentioned above)! It is key that when you're putting together an effective suspension setup that you remember everything works together to distribute loads across the chassis, and that *price* is not the most important factor in picking your suspension parts. You need it to work, and work well for your application. Picking the right part for the application is the key, and we're here to help with that.

An Exhaustive List


Exhaust is, and always has been, a crucial part of every build. Getting exhaust gasses out of the engine quicker allows more air in, and thus more power is made. The STi comes from the factory with an exhaust system that complies with all 50 states’ emissions requirements, and has very aggressive sound deadening characteristics to keep the noise down. For the average car buyer, this is fine. For the performance-minded enthusiast, it means there is a lot of room for improvement if we don’t mind a little more aggressive exhaust note (I promise we don’t mind). We install an aftermarket downpipe and cat-back exhaust system on basically every car we are looking to make more power with, as the OEM exhaust on the STi is very restrictive, especially the downpipe. Note: A tune is necessary to get your car running without a check-engine-light with most aftermarket downpipes, but Cobb has a tune that comes with their Accessport that you can use to remedy this, or you can of course go the route of a custom dyno tune from a Cobb Pro-Tuner which yields the best results by far.

Tuning and Data

Cobb Accessport and Custom Dyno Tuning

Tuning is a vital part of the equation with any car, especially the turbocharged type like the STi. These days, you can pick up a Cobb Accessport, plug it in, and literally get an almost instantaneous increase in horsepower. To really make full use of your engine upgrades, however, it is warranted to use your Accessport in combination with a tune from a Cobb Pro Tuner custom dyno tune. The Accessport gives the tuner full control to make all necessary adjustments to your factory ECU, as well as allow you to create a custom gauge to monitor your car’s vitals in real time. This is another one of those components we use on *every* build that comes through our doors.

Crank it up to 11

Turning up the boost

The factory turbo on the STi is actually pretty decent! Sure, maybe you won’t make those crazy high horsepower numbers you sometimes see these cars making online using a factory turbo, but it’s definitely capable of making a lot more power than it does in stock trim! To crank the boost up higher (in combination with a custom dyno tune), you need a few components. The first, obviously, is a boost controller. This lets the tuner crank up the boost with the amount of precision necessary for a proper tune. Next, we need an aftermarket Blow Off Valve that is built better than the stock unit, which tends to leak boost at higher boost levels. The final piece of the puzzle is a fuel pump that performs better at higher RPM and keeps fuel pressures nice and consistent through the rev range. These three things work together to create a very consistent tuning package to extract the very most out of your stock turbo!

Put The Brakes on The Competition


The Brembo brakes that come on the STi aren’t too shabby. There is still substantial room for improvement there as well though, especially for people who *really* push their cars. The braking zone is where the real drivers shine, and that’s where a set of superb brakes really stand apart. Brake deeper, brake later, and brake hard longer with a big brake kit. A good kit will include bigger calipers, steel-braided lines, aggressive pads, and two-piece vented disc rotors. The kits are designed to dissipate heat, keep the brake fluid from boiling, have much harder grab, and allow for much harder braking for much longer before fading occurs. Definitely a must for people pushing big power or people who track their vehicles at all. You definitely don't want to panic-brake to avoid a collision because you haven't upgraded your brakes to match your engine output. That's a sure-fire way to ruin your day AND your coolness factor. Don't be that guy: upgrade your brakes.

Burning Corn

Flex Fuel Kit

These days, almost all big power cars are running E85 as their fuel. It’s just a very easy, affordable way to make more power. It’s a much more stable fuel than gasoline that allows your tuner to add more boost and thus make more power!  It does require some fuel system modifications, you need a gas station near you that sells it, and it typically requires changing engine oil more often, but the power results are SERIOUS. A flex fuel kit-installed car can continue to use regular 93 octane, but when E85 is put in, it takes a reading of the ethanol content and automatically scales the tune accordingly with the present ethanol percentage. You can see some really chunky power gains using E85 and a good tune, making it one of the most popular ways to add power without modifying the car all that seriously. We believe that utilizing a flex fuel package as part of your build is a smart and affordable way to make decent power without a ton of time, work, and risk.

Carbon Copy

Aero/Exterior Customization

What makes a car unique? It can be something big, something small, or just the “spirit” a car is given by its owner. The owner of a unique car gives it its character by how it’s driven, but also by how it’s been changed by the owner to express themselves through how it looks. The aftermarket has exploded with tons of products out there for this car from full carbon fiber body components to innovative lighting, functional aerodynamic parts to purely cosmetic personalization parts. There’s an infinite number of ways you can configure your car to stand out from the crowd and look different from how everyone else is set up. Don't be a carbon copy of everyone else. Sorry, couldn't resist the pun.

These are what we believe to be the mods that give you the best bang-for-buck modifications to your STi, and parts we tend to install on all of our builds. The parts on this list are meant to have great results on their own, but also prepare your car for future growth as well whenever it is that you do that built motor with a big turbo! Let us know if you need help picking the right parts for your goals, or if you have any questions about what setup is right for you!

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