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Serious Subie - 2006 Subaru WRX STI

The Face-lifted 2006 STI Gets a GReddy Power Infusion

Al Mamoon
Jul 24, 2006
Photographer: Henry Z. DeKuyper

The Subaru WRX, the car that rekindled the all-wheel-drive turbo-four flame in the United States, got a substantial facelift heading into the 2006 model year. The '06 is easy to spot thanks to its all-new three-panel front grille setup. But not all the changes are as readily apparent. The car is two inches longer, comes in a total of three models in addition to the STI (WRX, WRX Limited, and WRX TR (Tuner Ready), gets a 2.5-liter 230hp engine, 17-inch alloy wheels, and upgraded brakes as standard fare. The big news is what Subaru didn't change, namely the STI. Although they did rename it by making the "i" a capital, the rally-bred speedster retains its EJ25 engine and the high-output turbo, which at 14.5 psi produces the same prodigious 300 hp and 300 lb-ft of torque.

Knowing the updates would only pour gasoline on the already sizzling hot STI, Trust Japan, the parent company of GReddy USA, got one of the first STIs to roll off the line. The car was delivered to the Narita-based company's R&D department and the technicians converged on it like ravenous lions tearing apart an ailing gazelle on the Serengeti--no hesitation, no mercy.

The factory issue IHI turbo was deemed worthy for the moment and left in place. So Trust attacked engine performance on the flanks with an R-SPL HG intercooler kit, Airinx-B intake, and Power Extreme Ti-R exhaust system. A PRofec e-01 boost controller was employed to up output to 1.2 bar, or 17.6 psi, while a full GReddy e-Manage kit was assigned to tune the combination. The net result is 350 hp at 5500 rpm.

Trust also addressed proper cooling by swapping the car's OE radiator with a high-capacity GReddy unit, a carbon-fiber air diversion plate, and a Type-S radiator cap. It should be noted that radiator panels and DIY ducting, as well as sealing gaps between fan, shroud, and radiator directs more air through the core. These efforts can improve cooling efficiency by 15 to 20 percent, which can be key in the heat of summer in stop-and-go traffic. Turbo cars can be especially vulnerable because the turbo creates more underhood heat and front-mount intercoolers can compromise the radiator's cooling ability. The cooling program extends to the oil system where GReddy added a Sport series filter, an S-Type oil cooler, and a trick oil catch tank.

Another popular destination for Trust technicians was the car's underpinnings. The party starts with a set of GReddy Type-S dampers. These coil-overs are monotube designs featuring a 46mm piston, 32-way adjustable damping, thick billet upper mounts, and lightweight springs. Next, the GRex portion of Trust's portfolio was opened up as the Subie received a front brake upgrade consisting of 330mm slotted rotors and 6-piston calipers with the trademark golden hue. The rear brake system was enhanced with 330mm rotors and 4-piston calipers. Any enhanced suspension would be in big trouble without a contact patch that is up to the challenge. To this end the Trust STI rolls on 235/40 Bridgestone Potenza RE01-R tires wrapped around 18x7 Volk Racing G-Games 57 rims with a +45mm offset.

The interior of the STI is one of the sportiest factory offerings on the road today so Trust installed its SM integrate lineup of gauges, a shift knob, and the aforementioned tuning electronics and called it a day.

Some fresh-from-the-drawing-board models take too long to spool-up the aftermarket but with the fanatical following of the WRX and STI the new Subaru flagship looks like its starting out at full boost. If you're lucky enough to throttle one of these rockets, start tuning, hang on, and enjoy the ride.

By Al Mamoon
28 Articles



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