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.
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.
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.
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.
All Types Of Bars
Unlike some Japanese suspension tuners, who increase roll stiffness by just using kidney-busting springs, Whiteline shares the same mentality as many American tuners (and probably similarly rough roads). The G4 kit anticipates the use of anti-roll bars. While Whiteline also makes an entire line of adjustable anti-roll bars, beefed-up endlinks and anti-roll bar mounts, we went with a set of 22mm front-and-rear chromoly Sustec Stabilizers from Tanabe.
The idea (on a street car) is that most people don't want to get underneath to make adjustments. We also wanted a predictable balance of front and rear roll rates that didn't set the car into a spin on the interchange if you had to lift and brake for traffic, or lift the inside rear wheel up over every driveway. The WRX bars were designed for 2004 models, but we didn't have any fitting issues on our '06, nor did the bars bind against the stock end-links at our ride height.
We also added front-and-rear strut tower braces to make sure the suspension does the work, not the chassis. Although we're usually skeptical about the effectiveness of strut tower braces, especially on super-stiff modern chassis, we've never been able to come up with a test accurate enough to measure the change in chassis deflection. The DC Sports titanium pieces we added did make a difference we could see in terms of more front tire shoulder wear during extreme cornering. Part of why it works so well is that the non-hinged single piece design doesn't have an added degree of rotational freedom between the mounts and the actual bar that transfers the load. At a weight penalty of only 2.7 pounds in front and 1.6 pounds in back, it wasn't something we'd sweat.
Testing Month
You can imagine how many tires we'd be able to test in one month if we weren't SCC. But to us, getting a true street tire impression isn't just a matter of putting on a bunch of new tires during one long day at the track and banging out performance numbers. It actually has more to do with spending time on the street to learn all the little things you'd never notice while flogging it on track. So we got through just one set, the Maxxis MA-Z1 Victra UHP tire.
To make the test fair, the people at Discount Tire Direct supplied us with two sets of 17x7 Enkei J10 wheels with a +38mm offset, chosen because they can mount the same-size tires as stock. The original 215/45/17 Bridgestone RE92 tires were re-mounted onto one set, while the identically sized Maxxis MA-Z1s were mounted onto the other, so we could baseline the stock tire against the test tire on the same day under the same conditions.
We also came across a pressure-sensitive film made by Sensor Products Inc. and used that to get a contact patch for each tire. The Pressurex Pre-Scale Pressure Indicating Film is basically a sheet of material placed between two touching surfaces. Once there is pressure, the film will leave an impression of the contact. It sounds like an expensive way to get an impression of a contact patch, but Pressurex actually has a lot of applications for automotive use, ranging from brake pads to manifolds. Once an imprint is made, the film can be sent back to Sensor Products for post-processing that can break down pressure distribution so you can see how much pressure is acting on which spot and just how uniform it really is.
Stock Bridgestone RE92
The worn stock RE92s blew us away once we made the suspension changes. We didn't think showroom stock tires could work this well, especially when you look at the decidedly un-sporty tread pattern. But the technology and development time spent on the RE92s is clear. The tire is quiet, decent in steering response, communicates wheel motion well, and has a progressive breakaway limit.
Maxxis MA-Z1 Victra
One look at the Maxxis MA-Z1 makes several things apparent. The shoulder blocks are larger, which should mean more cornering grip, and the center V-tread pattern is set at an aggressive angle, which helps with water evacuation. Tread grooves are deep and cut at 90-degree angles, which hold more water, but have more tread squirm and scaling issues under intense heat.
This is exactly what we felt on the street and the track. Although the MA-Z1s physically generated more grip, they're as loud as some R-compound tires at highway speeds, had mild groove tracking characteristics, didn't communicate well how close to or past the limit of grip we were, and had some steering vagueness in the first couple degrees of turn-in. We think these traits were concessions made by the manufacturer for increased wet performance, which we didn't get the chance to test, except at the car wash. We also noted a shorter sidewall on the Bridgestones, even though both tires were the same size, which added to the steering and suspension edge while the car was on the RE92s.
Our figure-eight and skidpad numbers give an idea of the hairs we're splitting here. While none of the configurations even broke 0.9g or posted eye-popping times, the end result is that the combination of a Whiteline/Tanabe suspension, Maxxis street tires and wide torque band puts our 2006 Project WRX at the top of the list for the best street project car in terms of fun, driveability, durability, practicality, civility and just about anything else that matters in a car you'll be commuting in.
| Stock suspension WRX | Project WRX w/ | Project WRX w/ | |
| w/Bridgestone RE92 | Bridgestone RE92 | Maxxis MA-Z1 | |
| Skidpad (g) | 0.79 | 0.85 | 0.87 |
| Figure 8 time (sec.) | 26.91 | 26.58 | 26.47 |
Photo Gallery: Project 2006 Subaru Impreza WRX - Sport Compact Car Magazine
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