Project Subaru STi Part One


Project STI
An attempt to catch the startup illumnation of the STi’s display.

 We started with a used 2004 STi that we bought from a private party.  Although the car was in mint condition and essentially stock, it was equipped with a set of Tanabe aftermarket lowering springs that lowered the car too much and were too soft.  This led to bottoming out of the front suspension under cornering loads of understeer.  Unfortunately this is typical of aftermarket lowering springs.  A car as good as the STi in stock form is easy for the typical aftermarket tuner to mess up!  We were unable to even come close to approaching the lap times of a stock STi at Streets of Willow raceway.  These springs will hit the garbage soon enough and we have our eyes on a set of coilovers with the full capabilities to do all the adjustments needed.

The previous owner curbed the stock wheels hard and probably ran the car through a carwash with unprotected rails scarring the wheels badly.  Mackin Industries saved the day and provided us with some ultra light forged bronze Volk CE28N wheels in 18×8.5” with a 44mm offset.  The CE28N is a high tech, superlight forged wheel favored by touring car racers and auto enthusiasts around the world.  Our new wheels weighed 18 lbs each, impressive for an 18×8-inch wheel.  Our racing experience also tells us that the CE28N is an exceptional strong wheel in all cases from on track to coming in close contact with an FIA curb or two!  We needed some sticky tires in order to accommodate our future planned suspension modifications and power upgrades.  We selected a set of 245/40-18 BDG G-Force KDW tires for all around wet and dry street performance. For track performance in the future we will stuff a 275 on all four corners.

As a first step we drained all of the stock fluids in the transmission, transaxle, differential and engine and replaced it all with synthetics from Motul. Motul’s 300V racing oil in 15w50 weight was run in the engine. Turbo engines are hard on oil which get contaminated quickly and tend to burn a lot of oil, especially when being track driven. The Subaru also doesn’t have an oil cooler and it needs some help. The thicker 15w50 should helps with this.  The transfercase, transmission and differentials were filled were filled with Motul Gear Comp 75W-140, Motul’s severe duty 100% synthetic gear oil. Next we baseline dynoed Project STi on XS Engineering’s 4WD dyno and were surprised with the results.  Project STi put out an impressive 246 hp and 241 lb ft of torque.

The dyno sheet shows the power and torque made before we got our hands on Project STi.

In our coming updates, we will try to see what some basic bolt ons do to Project STi’s power, start to tighten up handling and turn XS engineering’s tuning guru Eric Hsu loose on tweaking the STi’s factory ECU.

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