Driving Sports

The saying goes, “The cobbler’s children have no shoes,” the idea being the cobbler is too busy making shoes for his customers instead of his children.  This leads to the question, what kind of car does a tuner drive? In the case of Subaru tuner and guru Jeff Sponaugle, a brand new 2008 STI is what.  Jeff is no stranger to the Subaru world.  He ordered a 2002 WRX in December of 2001, sight unseen.  After taking delivery, the car lasted only a year before an imported Spec C drivetrain was installed. Through the year’s his 2002 has seen more than 10 engines; everything from hybrid USDM 2.5-liters to the rare EJ207 high-revving 2.0-liter.  For his latest project, he built and installed a custom turbocharged Tribeca 3.0-liter H6. That car competed in Subiesport Magazine's Subiefest2 Time Attack, and is a regular at local track days.

For 2008, Jeff decided to add the new 2008 model to his stable. Adding the new 2008 to the mix was a logical choice, given the changes to the platform.  As Jeff says, “A tuner is only as good as his experience allows.”

For any good tuner, time is not to be wasted.  Jeff picked up his 2008 STI on December 19th, drove 120 miles, and put it on the dyno.  After seeing how much room there was for improvement on the stock tune alone, the mission began.

The guys at PDXTuning were able to fab up a temporary exhaust system using a Perrin downpipe, along with some custom tubing and a pair of Magnaflow mufflers.  With these in place, a TurboXS Delta UTEC was added to get the tuning process started.  The car responded well to a good tune, but the stock turbo can only do so much by itself.

The new 2008 STI includes both intake and exhaust AVCS (variable valve timing), so as soon as the beta of the Cobb AccessPORT was available, Tim Bailey, Jeff’s friend and tuner at Surgeline Tuning, 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 room in the wheel wells.  Previous stock Subarus maxed out at 8.0 inches (without fender modifications), but the new 2008 STI comes with 55 offset 18x8.5-inch rims. For those who autocross in stock classes, this allows a great selection of wide rubber.  Suspension parts are just now coming to market for the 2008, but a set of H&R lowering springs were acquired and fitted, as well as a set of JIC Magic 9.5-inch wide, 45 offset 18-inch wheels shod in 275/35R18 BFG KDW2 rubber. To help pull in some of the factory understeer, a Perrin 19mm rear sway bay was installed in favor of the stock 17mm bar. The addition of the Perrin Positive Steering Response System (PSRS) added three degrees of front caster (totaling to 6.8 degrees!), while the Perrin subframe brace tightened up the lower control arms.

Interior
Instead of going the usual tuner route of having five or six of the most critical gauges, Jeff decided to go with the latest technology from PLX Devices — a pair of beautiful 60mm OLED full color gauges that can read from a variety of sensors —  installed within a Perrin Gauge Pod.   Since the 2008 STI has A-pillar airbags, you can’t add a pillar-mount gauge pod, so the two-gauge approach maximizes the return on real estate. For sensors, Jeff chose the PLX AFR, boost, oil temperature, water temperature, air temperature, and oil pressure data collectors. These sensors then feed the PLX brain box with data that can be shown on the two color displays.  With the touch of a single remote any parameter can be seen or recorded. The further addition of the PLX iMFD Datalogger allows complete data collection with offline viewing via your laptop. Since all the sensor modules daisy-chain, you can add more sensors as needed without more gauge clutter. The clarity of the PLX gauges is uncanny, and it is clear that this kind of display is the wave of the future.

Tuning
With the hard parts installed, the car was bolted to Perrin’s in-house Dynapak Dynomometer.  Running a smooth 22psi on pump fuel, power was tuned to 410whp and 405lb/ft of torque, with conservative timing and fuel settings. The S# Map was then programmed to target 25psi with the PWI-1 Meth system engaged. With the 50/50 water/methanol mix spraying, the car put down an amazing 471lb/ft of torque and 440whp! With that kind of torque and power, this 2008 is a mean machine rolling around the streets of Portland.

More mean for your green
The end result is a car that out-performs the older STI in basically every way. With a more sophisticated engine, ECU and suspension, the new car has all the capability as the older car without sacrificing anything. The charge that the new car is in some way softer or inferior is simply unfounded.

Thanks to AVCS tuning, the new STI can now make more power sooner with larger turbochargers than the older car was able to (see sidebar, Page 45-46). What’s more, the overall engine design is relatively unchanged so that most of, if not all of the engine parts currently on the market for the previous-generation STI will bolt right in. This engine is using off the shelf CP units for a 2004-2007 STI.

Also, since this car shares many components with the current Legacy GT and WRX, there are again many parts available right now that you can use in your STI. The PSRS for the Legacy is a direct bolt-in piece as is all the engine hardware.

Again, the STI is leagues ahead of other tuner marques in terms of ease of modification and product support. The Perrin turbo kit will be online as you read this and already the Cobb AccessPORT is available.

The outlook is bright for Subaru tuning in the coming years and with the launch of the new WRC car imminent, we can only assume that things are going to get better.

This article originally appeared in Subiesport Magazine . Jeff Sponaugle contributed to this article.

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