While the three to four Impreza-based project cars we've been involved with in the past were built to be edgy, pissed-off machines, capable of doing double duty on both track and street, we wanted something different with our Project 2006 WRX. The response from the new variable-cam 2.5-liter EJ25 engine easily eclipses the horrendous lag of the old 2.0-liter. Since the engine physically moves more air, boost is instantaneous and linear, and is much more suited to city acceleration than the peaky old EJ20-or the constant insanity of the STI.
The new WRX's steering feel is also improved, on-center vagueness is reduced. The transmission update means there's no more guessing about whether or not the car's in gear, or double-clutching to get into reverse. With so many improvements applied throughout, we decided to focus on tightening the suspension first.
Initially, our hope was to show that, for a pure street car on street tires, lowering springs and upgraded dampers are just as good as the fancy-pants coilovers we mount on just about every one of our project cars. We just needed slightly stiffer spring rates for our plans to use Project WRX as a tire-test platform.
Whiteline Automotive's now-discontinued G4 line uses an upright monotube damper that's height- and single damping- adjustable, using a steel body with aluminum spring perches and tender springs at each corner.
The only problem was, the lowering springs we initially picked were too low and, when coupled with the stock dampers, created a severely under-damped system. Despite our findings, the manufacturer claimed the springs were designed to work with stock damping rates. Umm... sure. In retrospect, the better option would have been to pick a set of high-quality sport dampers with more low-speed damping to better control body motion and to increase the roll rate with aftermarket anti-roll bars. This is a pretty good idea, since most stock springs are engineered by OEMs to give a good ride frequency and NVH for the street when coupled with stock bushings. Instead of wasting time looking around for the right damper/spring combo, we changed plans and went with coilovers, since, for the most part, a coilover's damping range is specifically designed to work with the included spring's rates.
Coilovers from Down Under
Over the years, we've tried just about every notable make of coilover suspension available in America. It's often a crapshoot-one brand might make a great set-up for a given application, yet feel like crap on another. We decided to try a set from Whiteline Automotive, based in Australia. One look at its product line-up shows that Whiteline doesn't just make springs and dampers. It takes a holistic approach to suspension tuning by addressing critical issues, like proper geometry whenever a car is lowered.
We got a set of Whiteline's top-of-the-line G4 coilovers through its American distributor, Global Performance Parts. The G4 suspension for the WRX/STI uses a steel-bodied upright monotube design with a 46mm diameter piston, and anodized aluminum threaded bodies with spring perches for height adjustment.
The G4 kit uses stock rubber upper mounts and is about the same height as the stock pieces (the front items are on the left). With our car roughly one inch lower than stock , we had to cut the rear bumpstops in half to avoid bottoming out when carrying rear passengers. We'd recommend maybe stepping up the rear spring rate or upping all four corners to avoid that problem.
All four corners use a small tender spring to maximize droop travel, an important thing on the WRX when running soft street-spring rates that require more suspension stroke. Chassis like the WRX, which have some off-road roots, seem to be happier with more suspension travel in street trim, since limited travel means almost no camber gain with its MacPherson strut suspension. This is why the stock '06 rolled so much.
Our first experience with the G4s was an eye-opener. We rarely experience such a comfortable street ride, especially one that maintains such composure on the skidpad or the figure eight. Merely add one or two clicks to the 12-position damping adjustment and the difference can be instantly felt between a nice, under-damped street ride and a responsive track feel, all on spring rates that don't beat your brains out. After some pleading with Whiteline's proficient engineers, we finagled some shock dyno data out of them-data which compared the G4's damping profile to the stock STI and to various leading aftermarket suspension kits. What was immediately apparent is that Whiteline uses an extremely linear damping profile. This means damping resistance increases consistently as piston speeds increase. Most modern dampers we've experienced use a digressive damping profile that emphasizes more low- and mid-speed damping to control body roll and surface undulations, while having relatively low high-speed damping to reduce all the bumps and jiggles your ass feels on the freeway.
It seems counterintuitive, since we like cars that don't roll or pitch (which is the reasoning behind digressive damping), but Whiteline engineers explained that they use a near-linear damping profile because: "We don't get hung up on low-speed compression, as our packages always use anti-roll bar upgrades for better roll control, which partially negates the need for higher transient spring rate effects." They also make anti-lift bushing kits to control some conditions of pitch. We're not entirely convinced, since damping typically has to do with how fast each wheel moves relative to the chassis, while spring/roll/pitch rates relate to how much force has to act on the wheel to move it. Either way, it works and it does a damn good job.
Whiteline uses a single Allen locking spring perch, eliminating the need for spanner wrenches.
Since the G4's piston design is an adjustable bleed bypass system, both compression and rebound damping profiles change when adjusted. The majority of the damping force change occurs in the rebound side, since (according to many) rebound is the larger component of force and has a larger impact on ride quality. We did notice that, unlike many dampers where the effects of damping adjustments are only apparent at mid-to-high piston speeds, Whiteline's shock dyno chart shows an immediate jump in rebound damping resistance, even at ultra-low piston speeds, making any change to the damping adjustment immediately noticeable in the ride.
We didn't bother corner-balancing our WRX, as it's street-bound only and constantly loaded with various numbers of fat-ass passengers looking to bum a ride. We just set the car roughly an inch lower than stock, maxed out the front camber within the stock adjustment range, and used a set of Whiteline 14mm rear eccentric camber bolts to max out the rear camber to above -1 degrees. Toe was set to 1/16th inch out up front and zero in the rear. We also cut the rear bumpstops in half after a couple days of fooling around-we realized the stock rear 4kg/mm springs had some issues with bottoming out when passengers were on board. Depending on your preference, we'd suggest changing the rear springs for a set of 5kg/mm pieces, although this will affect the balance of front-to-rear ride frequencies.
Now here's the bad news. It seems every time we find a really good suspension set-up, it's not available to the public (for example, our bad-ass but discontinued TRD suspension for Project MR2). As of this writing, Whiteline has decided to discontinue the G4 line and sell out its existing inventory. We've seen group buys online, but chances are, people are going to start wanting these in a bad way. So now's the time to e-mail and convince the Whiteline people Down Under to change their minds.
Whiteline was thorough enough to supply two types of spring perch shims, one for pre-2002 and one for 2003-on Imprezas, since later models used an angled stock upper perch that would otherwise unevenly load the main spring. The later models' angled non-concentric perches are CNC machined from aluminum to ensure proper spring seating. | 
DC Sports' titanium strut tower braces for the WRX/STI fit the 2006 model with no issues and weigh only 2.7 pounds for the front and 1.6 pounds for the three-piece rear. | 
The front bar is a single piece with stitch-welded brackets. Because there are no hinge points between the bar and the brackets at the top the towers (which would result in flexing), it's super-stiff. |