What Goes Into Building a Dirtfish Subaru STI?

Over the years, we’ve had multiple requests to show what it takes to build the cars we use everyday in our rally programs, so here’s what goes into building one of our Subaru STi school cars! When it comes to deciding on what car to start building to rally specifications, the Subaru STi is one of the best right out of the box; basically a streetcar that was bred from rally, it is set up with an extremely advanced all-wheel drive system that boasts a magnetically controlled active center differential, not to mention they leave the factory with a more than decent amount of power and torque.

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We start off by acquiring a stock STi that you would buy right off the showroom floor. The first step for building a rally car or any race car for that matter, is to strip it down to the bare bones. We take the majority of it’s interior out to lighten the car, get rid of the sound deadening, and make room for the rollcage.

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The interior isn’t the only place on the car that we remove unnecessary items; another one of the steps during teardown is to pull the entire motor to remove accessories such as the air conditioning, ABS and some of the emissions equipment.

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Next on the list is to drop the rear sub-frame to add gussets, and replace the stock rubber bushings with polycarbonate bushings to make them a little stiffer and stable. While the sub-frame is out of the car, we also remove the vehicles EVAP, because it is no longer needed.

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While the Brembo brakes that come stock on the STi are really good brakes, we replace them with 4-pot calipers and rotors from a WRX to allow us to fit 15” Method Rally Wheels and equip them with Hawk HP+ brake pads.

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Our cars are equipped with top of the line Reiger Rally Suspension, since history has proven that they are built to take the beating that our cars go through. However, they are not necessarily built to last year round like we use them! After installing suspension, we make a few more modifications, the first of which is putting a custom neoprene sleeve around the springs, keeping water, mud and dust from getting inside the strut. The second modification is to add a “snorkel” to the overflow/breather valve and routing it into the frame rail, which stops the valve from sucking up water and other debris.

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Of course a roll cage is needed for everything we do at DirtFish! However, since we aren’t required to meet FIA specifications being that we are on private property, the cage we build is strictly for safety, while also making it easier to get in and out of the car.

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The rear sub-frame is reinstalled with the new gussets and bushings.

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Since the car comes with a standard cable parking brake, we remove it and install a new CNC hydraulic handbrake with custom grips, plumbing it to the rear wheels only to help get the car around tight, low-speed corners.

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The environment that our cars are in everyday tends to be very hard on every component of the car, especially the engine. Whether it’s dust, water or mud, there is always the off-chance of that getting sucked into the air intake. To help combat the problem, we keep the stock airbox and filter, but we also route the intake from the stock airbox through the firewall, into the glove box where we have another filter. We do this because the cabin is the place with the cleanest air.

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We fabricate our own false floors for the driver and passenger foot wells for comfort and added passenger stability.

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Our roll cages are the tightest fit possible to provide the best safety for students and instructors.

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Another bit of fabricating that is done is for the custom wheel scrapers, which help prevent rocks from getting wedged between the wheels and brake calipers.

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To make the brake pedal in our cars have a more consistent feel throughout our fleet, we remove the brake booster and make our own custom brake lines and replace the master cylinder.

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Normally the windshield washer reservoir is located in the front of the car where there is a high chance of it getting damaged, but to minimized the risk, we move it into the rear of the cabin.

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Once the roll cage and all of the fabrication for the interior and engine bay are complete, we paint them in DirtFish grey to not only help prevent against any sort of corrosion, but it looks pretty good too!

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We fabricate our own custom skid plates to protect the engine and oil pan. We also add polycarbonate underbody protection. If we didn’t, the constant spray of gravel would eat through the sheet metal. In this photo, you can also see the new front lower control arms; since most of our cars are 2008-2010, we replace that front lower control arms with 2011-2014 model parts because they have a larger rear bushing and are a little beefier (which is something we definitely need on our cars). We also get rid of the mounting stud you would normally see and replace it with a bolt to make it sturdier.

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The first step of putting everything back together is to get the dashboard fitted around the roll cage and custom air intake.

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Once the car is reassembled and close to complete, it’s time for the wrap, which is done completely in-house from the design process to cutting it out on the plotter, to the install and final product.

Thanks to the extensive knowledge that our shop staff has in rally, rallycross and other motorsports, we are able to do everything in-house, whether it’s fabricating our own parts, getting the tightest fit possible on the roll cage, rerouting the intake, or simply painting the interior of the car. We do this to ensure our customers are receiving the best and highest quality product while they are here. Below are some photos of the final product:

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Words by Trevor Wert (DirtFish)

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