photographer: Henry Z. DeKuyper
America's Pacific Northwest has a long love affair with Subarus, going back to the days of the Brat, Justy and GL. When the WRX hit the market in 2001, the Northwest erupted like Mount St. Helens, becoming a real tuning hot spot for rally-bred street cars.
In this hyper-competitive environment, Hillsboro, Oregon-based Perrin Performance stands out due to its use of leading-edge technologies and versatility as a tuner and manufacturer. The company has built and tuned many high-profile Subie projects, including a WRX powered by a turbocharged 3.0-liter, flat-six engine pulled from a B9 Tribeca SUV. With the 2008 WRX, Perrin's goal was to unleash a blitzkrieg of parts development, which would focus on all aspects of performance.
The first item was the exhaust system. The new model incorporates a transverse-mount muffler that runs parallel to the rear bumper. Perrin decided to produce a modular exhaust system with an axle-back muffler piece and a separate center pipe, so the end user can buy a cat-back system piece by piece, or all at once. The three-inch system is constructed from SUS304 stainless steel and uses a V-band connection for easy installation and the deletion of a gasket.
Next, an up-pipe and header system (a direct carryover from the previous WRX) was installed in preparation for the big-dog mod, an upgraded turbo kit. The rotated-mount turbo kit is a Perrin trademark. It positions the turbo higher in the engine bay than the stock location, making the routing of intercooler and intake piping more efficient. For the 2008 WRX, the different placement of the throttle body and other intake parts meant the FMIC pipes were all-new designs. Finished in STI wrinkle red paint, the modified intercooler piping sadly ends up covering the view of the new turbocharger.
Designed primarily for the street and then the track, the new turbo kit required a responsive turbocharger, not a large-frame top-end unit. Perrin looked downstream of the popular GT35-series and chose the Garrett GT3071R. Thanks to its 71mm compressor wheel and 0.82 A/R housing, the 3071 has quicker footwork than the more popular Garrett 'response offering'-the 3076 and its 76mm comp wheel. Because of the new car's revised engine design, the downpipe was also a blank-sheet creation. It leads into a high-flow catalytic converter and then on to the aforementioned stainless steel exhaust system.
With the Garrett blower on board, the fuel system needed a revamp to keep up. Two Perrin fuel rails house a set of modified Perrin fuel injectors. WRX injectors can flow at 800cc/min, but Subaru installs a screen on the end which limits that flow to 540cc/min. So Perrin removes the screen. The injectors in this particular WRX are rated at 816cc/min. A Walbro 255lph pump anchors the fuel system.
A Hydra engine management unit was wired in. A popular replacement ECU in Puerto Rico, the Hydra is catching on in the US. The item was installed with a pass-through harness that keeps the stock ECU in the loop. This is important because the new WRX has an immobilizer that will not allow the engine to start without the factory ECU online.
A base 2006 WRX program was programmed to get the car fired up and test-driven. After a quick shakedown, it was time to tune. But the car's impending track debut at the 2007 Tuner Shootout meant a quick basic tune would be the extent of the initial session. With 320 wheel-hp at 16psi, the car ran well at the track, with plenty in reserve.
Back at Perrin after the shootout, the WRX was bolted to the company's Dynapack 4000 for some boost-up therapy. Bumping the EJ25 to 18psi netted a healthier 365 wheel-hp. With tuner Tim Bailey working the tune on the Hydra, cranking the boost to 21psi produced 385 wheel-hp and 389.4lb-ft of torque. Due to a hint of chatter on the knock sensor, Bailey backed the boost down to 19psi and the Subie was ready to roll.