Snow banks, sand dunes, river crossings and gravel pits are familiar territory to the Subaru Impreza WRX STi. Flip though any Subaru catalog, visit any nationwide dealership or cruise through any rally website and you'll most definitely catch a glimpse of an airborne STi mere milliseconds after it has rocketed off of an embankment. Watching in-car footage of WRC driver Petter Solberg or ex-multi champion Tommi Makinen is akin to being witness to one of the greatest automotive ballets ever - with their fluid inputs and the STi's resulting response bordering on unbelievable. Developed and refined through years of competition in the World Rally Championship, Subaru's top dog is best known for two things - getting dirty and blasting through forests sideways.
Born in mud, the STi packs years of off-road success into one street-ready platform. A potently turbocharged four-cylinder engine, active all-wheel drive system, lightweight forged wheels and a healthy Brembo braking setup - all have Subaru's rally interests to thank. But the beauty of all-wheel drive is not saved for rough surfaces alone. As can been seen in the Super Taikyu, Grand-Am, USTCC, and Speed World Challenge ranks, Subarus are also at home on racetrack asphalt. The STi's turbo engine can be tuned to deliver big power; big brakes and light wheels are always good on a racetrack; and all-wheel drive can help deliver monstrous corner exit acceleration. No matter what surface you look at, the STi can deliver.
Looking for a fun commuter car, Mike Crabtree picked up this 2005 Subaru Impreza WRX STi. The car was powerful, fun, incredibly responsive and the perfect daily driver. But it wouldn't stay that way very long. For more than twenty years, Crabtree has been quite the racing enthusiast. Having worked for Spice Engineering, the Nissan GTP race team, PPI, IndyCar and Dan Gurney's All American Racers, Crabtree knows a thing or two about building a racecar. Teamed up with The Barber Driving Experience instructor and co-driver Craig Dabbs, Crabtree has built and tested his STi on the harshest testbed of all - the racetrack.
One of the first areas modified was the suspension. Less than ideal for sticky tires and trackside curbing, the stock STi setup was dumped in favor of TEIN Type FLEX coilovers with a cockpit adjustable EDFC controller. Still not satisfied with the handling of the Subie after the addition of the TEIN's, Crabtree looked up SoCal suspension wizard John Mueller. Closely associated with some of the fastest track-modified Mitsubishi Lancer Evolutions in California, Mueller applied his all-wheel drive expertise to Crabtree's STi. Backed up by front and rear adjustable Whiteline swaybars, this STi is setup to harness and transform 700hp into low laptimes. A Whiteline ALK front control arm bushing kit was added to increase caster and reduce power-on understeer, while harder Whiteline urethane steering rack bushings combine with Group-N engine mounts to provide a sharper response.
Fitted with four-piston fixed Brembo brake calipers and meaty 13-inch front brake rotors, the STi possesses braking capability far beyond what normal drivers would ever ask for. Crabtree and Dabb's on-track incursions, however, asked for Brembo's Gran Turismo front brake kit. The rear of this STi retains the factory two-piston fixed caliper Brembo setup. Featuring stronger and lighter four-piston calipers, braided stainless-steel brake lines, two-piece brake rotors and Brembo brake pads, the Gran Turismo kit has proved its worth at many of Southern California's local tracks. With super sticky 245/40/17 Hoosier road racing slicks mounted on stock lightweight forged 17-inch STi BBS wheels, this Subaru can stop and turn with the best.
By now, you must be clutching this magazine, pondering and scheming how is it exactly that a Subaru needs this suspension, these tires, these brakes - and how it makes more than 700hp. The key is the fully built engine, dubbed the R5 by Crawford Performance of Oceanside, California. One of the premiere Subaru engine builders, with years of experience in the rally and sandrail world, Crawford started the recipe with a boost-friendly 2.5L engine block. The block was machined to accept replaceable wet sleeves, forged CP pistons hung on a 84mm Crawford stroker crankshaft, 4340 forged Pauter connecting rods and was then finished off with piston oil squirters. The final displacement for the R5 engine is a massive (for a four-cylinder Subaru) 2.8L.
Still using stock STi cylinder heads with no porting work, the R5 engine was given a Crawford Performance air/oil separator kit and TGV deletes before facing boost. Crawford Performance's own CP35R turbo kit was fitted to the R5 engine to handle pressurized power duties. Based around a Garrett GT35R turbocharger, the kit makes use of a Crawford Performance up-pipe, downpipe, Tial external 44mm wastegate and 3-inch exhaust system. The CP35R kit also includes all the necessary piping to connect the GT35R blower to a massive stealth black APS front-mount intercooler that swallows up all the available space in the front bumper.
Ingesting more boosted air than Satan himself could have deemed possible, this STi pushes the limits of power with lots of fuel. A Walbro 255lph in-tank fuel pump forces huge amounts of gas to the Crawford Performance billet fuel rails before it's shot out of 720cc/min fuel injectors. Tuned with a MoTeC M600 engine management system by I-Speed USA, 710hp and 742lb-ft. of torque at the flywheel was realized on I-Speed USA's Dynapack dyno.
Stout as it is, the nearly indestructible stock STi six-speed transmission was taken apart to hold the amount of torque seen here. A Crawford Performance six-puck clutch and lightened stock flywheel were added in the mix along with Driveshaft Shop axles to ensure that only the tires go up in smoke when the throttle is mashed. In a move rarely seen in the Subaru crowd, the six-speed casing was split open and fitted with a straight cut five-speed dogbox gearset. Using stronger gears than the STi six-speed and with proper selection of the ratios, this gearbox choice should prove both faster and more reliable than any OEM Subaru setup.
Although not quite the kind of show car that would be seen rockin' four headrest-mounted TV's and multiple subwoofers, Crabtree's STi does sport a few completely functional interior and exterior upgrades. A custom front bumper has been installed to make better use of front airflow and brake/oil cooler ducting. Working in partnership with APR Performance's front carbon fiber canards, carbon front splitter and carbon fiber rear wing, the exterior package has seen more than 135mph at Willow Springs International Raceway and has proven its worth. The Seibon carbon fiber hood was installed to help vent out hot air as well as reduce weight, a sore point for this 3200lb+ time trial car.
Inside, the entire rear seat and stereo system have been gutted and tossed out. Pulling duty as replacements are the 14-point Steen Chassis rollcage and the Sparco Pro 2000 racing seats. Holding the driver and passenger firmly in place during hard track sessions, the Sparco seats provide an easy access point to the Sparco steering wheel and the Motec dash display system resting just behind.
At a recent time attack event, Crabtree and Dabbs found themselves stacked up against an R32 Skyline GT-R and a Lancer Evolution VIII that both packed wider tires, more power, and further race modification. Dabbs did his best behind the wheel, but still ended up 0.4 of a second behind the Evolution. That may not seem like much, but to a tuner, every little difference counts. Already challenging Corvettes and Porsches at local time trial events, this STi is soon to resurface with more rubber, custom engineered bodywork and less weight. Just goes to show you, if it's possible to drive on it, there will be a Subaru racing on it.
Hot BoxCrawford PerformanceCrawfordperformance.Com
I-Speed UsaI-Speed.Us
The Barber Driving ExperienceBarberdrivingexperience.Com
Group 5 MotorsportGroup5motorsport.Com
Dixon ArtDixonart.Com
Behind the BuildHead to the message boards at www.importtuner.com to chat about this feature VEHICLE
Name. Michael Crabtree
Age. Forty-five
Hometown. Tustin, Ca
Occupation. Composite Engineering
Hobbies. Racing, Hockey, RC Cars
Build Time. One year
Feedback. blacksti@gmail.com
Quote. "My kids and I love racing. What better way to get us all together!"