It is easy to forget, after doing a few non-vehicle evaluation articles, just how much fun shaking down a well-modified car can be. It's also easy to forget, after driving several well-sorted track cars, how tough it can be to successfully modify a car intended only for legal street use. We take for granted that despite the rule book that governs what changes can be made to a race car, the regulations that must be adhered to and the requirements that must be met for a street-driven car form an often far more difficult set of confines in which to maneuver. It is with this thought in mind that I am so often impressed with the level of ingenuity of many of the tuners shops that rethink the average OEM street rod. GoodSpeed Performance Lab in Phoenix-home to a group of tuners, engineers and rethinkers of just about anything that is fast-seems to have the street thing down well, and a customer's '08 Subaru WRX STI is just one example.
John Firpach and brainy Joe Morell (formerly with Dynocomp) are the owners and tech-savvy driving forces behind GoodSpeed Performance Lab. For those of you who are loyal Modified readers, you may recall an impressive track-prepared Subaru Impreza wagon that we shook down several issues ago that was engineered by GoodSpeed.
This time it was all about a reliable road-going car, and John and Joe brought out one of their street-only silver STIs. Although the car sported aftermarket springs and bars, the real focus on the machine was usable street power, and as such, the under-the-hood goodies proved to be ample indication of what GoodSpeed was intending to do.
Much of what was modded on the motor of the very stock-looking Subie involved custom GoodSpeed parts, and the heart of those engine mods resides in GoodSpeed's GT35R twin-scroll turbocharger kit and its GT3578R twin-scroll turbo unit. GoodSpeed also custom-fabbed a divided stainless steel up-pipe and stainless steel headers. Although the owner insisted on keeping the cats intact, the GoodSpeed guys were able to still build a custom 4-inch stainless steel downpipe, complete with that pesky cat. The rest of the exhaust gas route was changed to an after-cat Invidia Q300 with a subtle but terrific-looking set of exhaust tips. No coffee can crap here, just a refined and purposeful-looking quad exhaust poking out from below the rear bumper.
On the suction side of the motor, GoodSpeed used its custom 4-inch high-flow cold air intake (although the Phoenix summer weather ensures that absolutely nothing air-based is cool), and the charged air is routed to and from the custom intercooler by GoodSpeed's own piping system. Some 850cc injectors, a Walboro pump and a modified fuel rail aid combustion. Finally, the software package for the '08 was enhanced by one of Cobb Tuning's AccessPort systems. The net result of the motor mods was a beautifully clean engine bay, and according to Firpach, an emissions-compliant and dyno-confirmed 440 hp at the crank on our Arizona-best 91-octane pump fuel. Not bad at all for a motor that uses a stock block and heads and is truly a reliable daily driver. The question then is, How did I like it?
First off, I thought the car looked great. The Cobb Tuning lowering springs and the all-black 18-inch O.Z. Superleggera wheels wrapped in Dunlop's Direzza Sport 225-40 meats gave the Subie a clean, sleeper look, but one that would garner a second glance from those who know cars. Can't say I'm a fan of the hatchback STI style, but in silver it does at least look better, and of course the new body style allows for those bulging squared fenders and the subsequent wide and substantial fascia.
Start-up yielded a very quiet exhaust note; it was clearly different and throatier than the stock tone, but still very quiet. The stock clutch felt light, precise and familiar and take up was without drama. Aside from the increased ride stiffness from the springs and Cobb Tuning's front and rear sway bars, the car felt almost completely stock. Once pushed through corners, the grip of the Dunlops was overmatched by the stiffened suspension, and the Subie exhibited a moderate to severe understeer. Actually, the handling balance was probably fine for the street. Really, even a safe scenario in the scheme of things on the road. However, the stock dampers could probably have used an upgrade, and the alignment could possibly have been more aggressive to achieve a better package for the track.
That's just it, though. Ultimately, this particular car was never meant for racetrack use. Even though we happened to shake the car down in that environment, the car was built for reliable street use, and looking at the machine in that light allowed me to forgive a bit of handling imbalance.
It was the motor that we all came to really sample, and from the seat-of-the-pants feel, the car seemed to make good on a horsepower number in the 400s at the crank. Considering parasitic loss in the drivetrain, something to which both Jon and Joe could speak with more authority, it felt as though the car was in the mid-300hp range to the wheels. Stronger than stock, to be sure, but also different in its delivery and the noise it made getting the job done.
Power was largely flat below 4500 rpm, but once the needle climbed past that magic number, boost developed with some solid authority. I only had about 2000 rpm to play with before shifting at a conservative 6500 rpm, just as the Subie-installed red shift light urged that another gear be grabbed. With that in mind, the power came on in short frantic bursts and the car made me work to ensure I was in the proper gear.
Almost better than the acceleration were the sounds from under the hood. I actually enjoyed driving the car at part throttle with the characteristic and charismatic (at least to me) Subaru flat-four loping accompanied by the sound of air under pressure being pushed and directed at the whim of my right foot. The exhaust, which produced a low growl under load at lower rpm, became more of a vicious rip in tone if not volume as boost and power built. The engine made itself known with some great sounds, and it was absolutely one of the best parts of driving the silver Subaru hatch.
There is no doubt in my mind that the car would develop boost quicker, a trait that I have come to associate with the GT35R turbo charger, had the cats been deleted. However, the ultimate owner was clear in wanting a legal car that would pass emissions. And so now you have some tough confines in which to deal-make more power, do it on 91 pump fuel and make sure it can be run in the considerable Phoenix heat. Competing with those criteria is the true measure of success or failure in this equation, and as far as I'm concerned Jon and Joe did their homework and built something worth driving.