Subiesport Magazine - April/May 2008 - (Page 44)

2008 SUBARU IMPREZA STI jumped in to help build some base maps. The tuning of the AVCS allows a tuner to dial in more valve overlap on spool-up, but less at higher rpm as the scavenging effect tapers off. The switch to the Cobb AccessPORT allowed not only control of the AVCS, but also mapping of the new Subaru SI-Drive system. This system allows the driver to select three different performance profiles with the flick of a knob on the center console. The Cobb AccessPORT allows a tuner to build different boost maps based on this switch, allowing a dial-a-power feature not seen in Subarus before. To help the small-but-effective turbo work cooler, a Perrin PWI-1 Water/Meth injection system was added. This system is one of the easiest and most fail-safe systems on the market. Built by the big brains at Aquamist, it provides linear fuel to water control, high- and low-flow sensing, clogged jet detection, and a low tank sensor. With a 50/50 shot of methanol and water spraying through a 0.8mm nozzle, the stock turbo was able to deliver a massive 400lb/ft of torque at 22.5psi. While the new STI’s VF48 turbo makes fabulous torque, it can’t maintain that torque at high rpm. To get more top end power, a bigger turbo is the path to take. Jeff enlisted longtime friend and Subaru parts manufacturer Jeff Perrin to help out. The latest iteration of the Perrin rotated turbo kit, along with a Perrin FMIC, was installed. To help get the exhaust gas to the turbine, a Perrin equal length header was bolted in, as well as a Perrin full dual-cat exhaust system. Excess pressure is released through a Perrin blow-off valve. A Garrett GT30R turbocharger with the 3-inch GT .82AR turbine was selected for maximum street drivability and good top-end power. To get fuel to the fire, the latest Deatschwerks 850cc top feed injectors were installed in Perrin fuel rails, along with a Walbro 255lph fuel pump. Boost was controlled by a Perrin EBCS solenoid through the AccessPORT tuned stock ECU. To enhance the reliability of the bottom end, the stock pistons were swapped for CP 2618 forged slugs and ARP head studs were used to hold in the boost. Most amazing of all, this occurred with only 700 miles on the odometer! Suspension One of the great advances with the 2008 is the width of the factory wheels, along with the extra FRESH UNDER THE HOOD To go along with the new body style of the 2008, Subaru updated the engine and drivetrain with some performance enhancements. The new EJ257 engine, coded EJ257BG1LB, has a number of new features: The addition of exhaust cam AVCS, allowing up to 40 degrees of retardation of the exhaust cam. A new, larger 11mm oil pump. New, stronger connecting rods. New rings. An updated head casting to support the AVCS, with changes to the water jacket feed holes. Intake and Exhaust cams are new, as are the intake and exhaust valve springs. The turbo is an IHI VF48, which appears to have a slightly larger compressor cover from the previous year VF43. • The transmission (TY856UW1AA) has the same gear ratios as the 2007 STI, but improved synchronizers. • The intake uses a new MAF sensor style compared to the 2007 STI version, so older intakes will not work. • The brake rotors are slightly bigger front and rear. Fortunately, for those looking to build up a 2008 STI engine, a number of critical things are the same as in previous years: • • • • • • • PHOTO: TRAVIS GENY Stock STI tire (right—Dunlop SP Sport 600 245/45R18) gets upgraded to KDW2 275/35R18. Fatter is better. 44 MAY 2008 • The pistons are the same as 2004-2007, so all the current aftermarket pistons will drop right in. • The head gasket is different for 2008, but the crankcase layout is the same. This means heads and blocks can be interchanged. • Intake and exhaust valves are the same from previous years, so aftermarket valvetrain components will work fine. PHOTO: TRAVIS GENY

Table of Contents Feed for the Digital Edition of Subiesport Magazine - April/May 2008

Subiesport Magazine - April/May 2008 Contents Travis Geny Letters Readers' Rides Subaru News Wicked in White Pink Rules Harman Motive Nouveau Tuning the 2008 STI 2008 Rally Guide Alcan 5000 Rally Alcan Unleashed WRC Rally Monte Carlo WRC Rally Sweden WRC Rally Mexico 100 Acre Wood Kumakubo! D1 Drifting Where to Buy Subiesport 2008 Impreza WRX 2007 Legacy GT 1993 Impreza Wagon Fueled Up Ad Directory Spotted!

Subiesport Magazine - April/May 2008

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