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SPEC SHEET: Addicted to Boost

It's one of the most expensive drugs on the planet. Horsepower. We all know the feeling. What might give you your fix today will soon wear off and what felt fast yesterday feels almost mundane the next. Your entire perception of speed changes. You find yourself asking your passengers if that "felt fast" and they'll typically look at you with an astonished expression. This story is the same for any car guy and this car really shows it best.


Today's Spec Sheet episode follows Tyler's 2012 STi. He started this build process just as many of our clients do. We installed a handful of bolt-on parts to the stock motor, tuned the car, and the night and day difference in speed was there. Sure enough, it became mundane and it was time for more. We then updated the car to include our S2 engine and a Blouch Dom2.5XT-R stock location turbocharger. Making around 120whp over what it had been making before, that felt like a large jump and kept Tyler satisfied for a bit; but sure enough, it was time for even more.

The next phase of this build required an engine update to our S4 shortblock and S2+ cylinder heads. We then mated this engine to an Exedy twin disk clutch and a Garrett GTX Gen II 3582R turbocharger. This set up produced just over 700whp (around 250whp over the previous set up) and we both really thought that would be it for the car. About a year later, we found out that was far from the truth...


The current set up on the car is an alteration of a very common 700whp package we put together in the shop often. We updated a few components and were able to extract another 100whp reliably from the set up. Lets talk about that set up.

Starting with the engine, this car utilizes our S4 Shortblock, which is then mated our S2+ Cylinder Heads with the help of ARP 625 head studs and the factory MLS head gasket with our proprietary head gasket modifications for optimal gasket sealing. To help out the oiling system, we added our PROCOM RACING PRO-Series Billet Oil Filter Adapter with a Wix filter. This improves engine oiling, increases oil capacity, and also increases oil filtration. A MUST-HAVE modification for your modified Subaru.

From here, we move to engine management and fuel system. This particular engine runs on the stock ECU. The ECU is then tuned via a Cobb AccessPORT with a Cobb Flex Fuel Kit. This allows us the ability to run the car on either 93oct pump fuel, E100, and any ethanol blend in-between with seamless integration. The tune will automatically blend between it's pump fuel tune and E100 tune based on the ethanol content reported to the ECU. What this means is that if you're running E85 in the car and you need to fill up with pump fuel for any reason, you don't need to change maps on your AccessPORT, the ECU will make the necessary adjustments by itself automatically.

The fuel system on this car is comprised of a Radium dual-pump hanger in the fuel tank. That hanger houses two of the newly released Walbro "525" ethanol-compatible fuel pumps. These pumps flow about 10% more fuel than standard Walbro 450 fuel pump and help add a bit of head room to this fuel system for safetys sake. Fuel is then ran to our Procom Racing "Firewall-Forward" fuel kit, that then feeds a set of Injector Dynamics ID1700 injectors.

Now lets get into the induction system. This is an area we're most excited about as this car sports one of the very first production Procom Racing rotated turbo kits that houses a Precision 6466 Billet Gen2 Turbocharger. While in-depth details on this kit will be released at a later date, it is comprised of all mandrel bent stainless piping and everything comes ceramic coated as a standard option. Fitment is excellent and the turbo placement is both functional and menacing in the engine bay. Building upon that is our Procom Racing "Flipped Manifold" intercooler kit with our "Street-Series" intercooler core. Both of these kits will be released in the fall of 2018 and we'll talk more closely about details then. Stay tuned for that.

The STi 6-speed drivetrain is very capable right out of the box so this portion is quick and easy. We simply updated his Exedy Twin-Disk clutch from the previous set up to an Exedy Triple-Disk clutch with a heavy duty pressure plate. Comparitive to the twin, the triple provides even better clutch feel with the same life expectancy and can handle about 100ftlbs more torque at the wheels. The rest of the drive-train is comprised of Tein Flex coilovers, Work 19 wheels, a set of Michelin Pilot Sport Cup 2's.

For this build, we kept the interior as close to stock as possible and only added the essentials. The interior of the car houses an AEM failsafe gauge. This gauge allows you to view boost and air-fuel ratios all-in-one but it also provides some pretty trick engine safety features. When properly set up, this gauges keeps a close eye on the engine's air fuel ratio and should the car go excessively lean, it will actually cut boost and signal the driver of the fault. This gauge helps keep a close eye on the engine and is quick enough to jump in and protect it should the need ever arise.

POWER AT THE WHEELS: 801whp / 685wtq @ 40psi

Due to fuel system limitations we dialed back the car to ~39psi to leave a bit of cushion in the fuel system for added reliability. This still yielded us 780whp and 670wqt. A small price to pay for added safety and reliability. I hope you've enjoyed this blog post and stay tuned for many more like it to come! Now check out the full spec sheet below for full detail on this build!




-Procom Racing S4 Shortblock

- AEBS Sleeved Block Case Halves

- STi Forged Crankshaft

- Manley Turbo-Tuff Connecting Rods

- Manley Turbo-Tuff Pistons

- King Main and Connecting Rod Bearings

-Procom Racing S2+ Cylinder Heads

- BC S3 Camshafts

- BC +1mm Intake and Exhaust Valves

- BC Beehive Valve Springs

- Procom Racing S2+ CNC Cylinder Head Porting Program

-Procom Racing PRO-Series Oil Filter Adaptor w/ Wix Street Filter

-APR Custom Age 625+ Headstuds


-CSF Aluminum Radiator


-Cobb V3 AccessPORT

-Cobb Flex Fuel Kit with Fuel Pressure Monitoring

-Omni 4-bar MAP Sensor


-Radium Engineering Dual Pump Fuel Hanger

-Walbro 525 Fuel Pumps (x2)

-Procom Racing "Firewall Forward" Fuel Kit

- Perrin 6-port Fuel Pressure Regulator

- Torque Solutions Fuel Rails

- AN Fuel Line (-6an)

-Injector Dynamics ID1700 Fuel Injectors (1700cc)


-PROCOM RACING Rotated Turbo Kit

-Tomei EL Exhaust Manifold

-PROCOM RACING Intercooler Kit w/ Street-Series Core

-Precision 6466 Gen2 Turbocharger

-Tial Q 50mm Blow-Off Valve

-Tial 44mm MVR Wastegate

-Invidia R400 Cat-Back Exhaust System

-Torque Solutions CNC TGV Housings


-Exedy HD Triple Disk Clutch Kit


-AEM Failsafe Gauge

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