This journal documents the extensive modifications undertaken to transform a 2008 Sti into a dedicated track car. The journey encompasses a comprehensive upgrade of various systems, from suspension and engine enhancements to cooling and safety installations, all aimed at maximizing on-track performance.
The initial phase focused on the foundation – the suspension. The stock struts were replaced with BC-BR coilovers, providing adjustable damping and ride height for optimized handling. Further enhancing the front suspension, new Lower Control Arms (LCAs) were installed, along with stiffer Whiteline bushings in the front of the LCAs. Notably, the LCAs were upgraded to the 2011 Subaru specification, painted red to match the red anodized rear adjustable Agency arms, ensuring visual consistency and enhanced performance. Concurrently, seats and harnesses were installed, prioritizing driver safety and stability during track sessions.
Engine modifications were equally extensive, targeting improved power and reliability under track conditions. Injector body “TGV deletes” were implemented to streamline airflow, removing obstructions and smoothing passages to match the manifold and heads with the injector bodies. A Moroso aluminum oil pan was added for increased oil capacity and improved oil control, complemented by stiffer motor mounts to minimize engine movement during aggressive driving. The installation of motor mounts proved challenging due to limited space, highlighting the intricacies of performance modifications. An oil filter bypass block was attached, paving the way for an upgraded oil cooling system. A NOS Setrab oil cooler, significantly oversized at 12x12x2 inches with 40 rows, was incorporated for superior oil temperature management, featuring a third tap for a sensor. To further safeguard against oil pressure drops, an Accusump, a pressurized oil reservoir, was integrated into the system. Fuel delivery was also addressed with a new higher volume Walbro 255 fuel pump, ensuring adequate fuel supply for increased power demands. An adapter kit was ordered for a Tial Blow-Off Valve to the FMIC (Front Mount Intercooler), preparing for forced induction enhancements.
Building upon previous modifications from a 2011 setup, further high-performance components were added. The cylinder heads and manifolds underwent porting and blueprinting, including a racing valve job and radiused exhaust seats. Manley springs and titanium retainers were installed to enhance valve train stability at high RPMs. A Blouch Dominator 2.5 XT-R turbocharger, featuring a 3″ air inlet and 8cm turbine A/R, was selected for its performance capabilities. Injector Dynamics 1000cc injectors were chosen to match the increased airflow, supplied by a Walbro 255 pump, later upgraded to a 450, with an in-tank mounting bracket. An Aeromotive 13109 A1000-6 Injected Bypass Regulator was implemented for precise fuel pressure control. An Agency Power 3″ polished aluminum hard turbo inlet and a KS Tech MegaMAF 73mm Big MAF Cold Air Intake were added to optimize air intake. A Turbo XS type FMIC and Grimmspeed EBCS (Electronic Boost Control Solenoid) were incorporated for improved boost control and intercooling efficiency. NGK Iridium IX Spark Plugs LFR7AIX # 2309, one step colder than the stock STI plug, were selected for enhanced combustion.
The oil cooling system was further refined with a Setrab 40 row oil cooler, paired with a Mocal OT2 176°F thermostat bypass valve for optimal oil temperature regulation. A Canton 90-degree rotating remote oil filter adapter was used to relocate the oil filter for easier access and improved oil routing. The stock oil heat exchanger was removed, and AN lines were run up the front of the timing cover for a cleaner and more efficient setup. A Canton Remote Oil Filter mount was installed, utilizing Ford-style filters, specifically K&N HP 3001 filters. Mocal “Titanium” line of AN hose ends and Racelight hose for -10 AN were used throughout the oil system for durability and reliability. The oil filter union was updated with Subaru part 15018AA090, eliminating the long tube union associated with the heat exchanger. An Accusump and an updated KillerB oil pan, windage tray, and pickup tube replaced the Moroso aluminum pan, further enhancing oil system performance and reliability. A Moroso A/O separator was initially used but upgraded to a CRAWFORD A/OS which vents into a JEGS breather-catch tank, effectively managing oil blow-by. A Perrin Crank pulley, later upgraded to a Fluidamper, was installed to reduce crankshaft vibrations. The TGV delete mod and port matching were also performed to optimize intake airflow.
After initial track events with the stock engine and dyno tuning, ringland failure occurred due to oil ingestion via an inadequate A/O separator. This prompted the installation of a new OEM shortblock with CP forged pistons and a rebuilt head with porting and a valve job by Kiwi Engineering. This engine configuration produced 395WHP/391FPT on EFI’s dyno and briefly withstood 26+ PSI boost on track. All evap/emissions parts were removed, and a fuel line loop with a check valve was installed for fuel tank venting. A roll cage was then installed, and modifications to the front end were undertaken to accommodate the Setrab oil cooler. The vapor collection system was removed and replaced with a vent hose loop extending to the roof with a check valve. SPA Technique dual/digital gauges were installed to monitor critical parameters: oil pressure, oil temperature, water temperature, and boost, providing essential real-time feedback during track sessions.
In conclusion, this 2008 STI underwent a significant transformation into a track-focused machine. Every modification, from suspension and braking to engine and cooling systems, was carefully selected and implemented to enhance performance, reliability, and safety for demanding track use, reflecting a dedicated pursuit of on-track excellence.
