Subaru Impreza 485 HP 400 LB-FT Of Torque
Subaru's Impreza has been kicking up dirt on the world rally circuit well before the WRX was brought to American soil. Few Americans realize how capable the older Impreza models really were or at least could become after some modifications. Like many cars, they were noticeably lighter in weight back then, and offered a driving feel that many say are simply lacking in today's cars.
This '96 Impreza is possibly the most awe-inspiring example in the country. Originally purchased in 2003 by Michael Warfield of GST Motorsports, it was intended to be nothing more than his simple daily driver. It wasn't until years later, in 2006, that it began the transformation into this time attack monster. It all began when GST and partners GOTO:Racing and Calculated Risk were scratching their heads trying to figure out what car to enter in the NASA 25-Hour Endurance race that year. Brian Lock of GOTO:Racing suggested that Michael build up his old Impreza. With everyone in agreement, Michael called on engine-tuning legend Cosworth for some motor help. The car was stripped and the frantic wrenching began.
They managed to get the car ready with no time to spare, with the final dyno run being performed at 2 a.m. the night before the race. In a field of 55 cars, it qualified in Fourth Place, although mechanical gremlins caused the car to run only six hours of the actual race. Afterward, they decided it would become a dedicated time attack race car, and the crew got back to work.
With Cosworth still on board for the engine build and Prodrive now helping with the suspension, Michael knew it would be a serious performer as a time attack car. The centerpiece of the motor is the Garrett GT35R turbocharger, although GST has also been known to use a GT30R (along with 8.1:1 compression) configuration for less extreme duty. Air enters through the 4-inch K&N filter and is cooled through a Blitz intercooler, while excess is dealt with through a TiAL wastegate and blow-off valve. The plumbing was custom-fabricated by GST, including the 3-inch exhaust system, while the crosspipe is Injen equipment.
In order to cope with the extreme boost, the engine internals have been heavily fortified with forged Cosworth parts, including the crankshaft and connecting rods. The forged JE pistons (10:1 compression) and rings are also well suited at handling the high pressure. The stock oil system has been scrapped in favor of a high-capacity pump, pan, and windage tray, all from Cosworth. The oil is further kept cool with a Setrab core with a Mocal sandwich adapter. The Cosworth-spec cylinder head received just as much attention as the block. It features a complete Cosworth valvetrain, including camshafts, valves, springs, retainers, keepers, and rockers. It has also had a full CNC port and polish, all finished by hand.
The Bosch Motorsports 044 high-flow fuel pumps are further boosted by a pair of Walbro 255lph pumps, sending the high-octane gas to RC Engineering 1,000cc/min injectors. The swirl pot and fuel rails were custom fabricated by GST, and Aeromotive's fuel pressure regulator keeps it all in check. Ignition was left stock and is controlled by the Hydra Nemesis engine management system.
The latest dyno run shows that this setup is good for a consistent, reliable figure of 485 hp and 400 lb-ft of torque, going to all four wheels. In order to cope with this power, a new Spec C six-speed JDM transmission from Subaru was installed and customized. The clutch is an ACT unsprung six-puck unit, and the flywheel and pressure plate are also from ACT. Both the front and rear differential have been swapped for clutch-type units from Cusco.
Brake layout for the front consists of 340mm Stasis discs and four-piston Stasis calipers. For the rear, GST opted for STI-spec StopTech 316mm discs and two-piston Brembo calipers. Michael counts on Endless to supply the pads and Stasis for the braided brake lines.
With all 485 hp pushing around a mere 2,660 pounds, this Subaru lunges around the track like an angry bulldog. Luckily, it still handles itself gracefully, thanks to the MacPherson strut suspension, designed courtesy of Prodrive. This setup employs Ohlins triple-adjustable shocks and adjustment shims at all four corners, with spring rates set at a stiff 650 lb/in for the front and 550 for the rear. Whiteline Automotive offered their support from down under, and provided 27mm anti-roll bars at both ends, as well as an anti-lift kit, bumpsteer kit and endlinks. At the rear, Cusco was happy to supply their lateral links and trailing arms. Depending on the application, Michael will either be using Rota Torque wheels or GC05's from Prodrive. Both are 18x9.5, and are wrapped in super-sticky R1 tires from BFGoodrich, sized 275/35 for all four.
When the bodywork came back from Calculated Risk, the Impreza became a whole new animal, featuring a fully custom-designed aero package for the front, a rear diffuser, and an impressive flat-underbody kit. The carbon-fiber hood and trunk lid come courtesy of VFiber, and TEC Engineering provided the side skirts, as well as the mounts for GST's custom GT rear wing.
Calculated Risk handled the interior, though that refers to little more than a pair of Racetech seats and six-point seatbelts. They also did the rollcage work and Firesafe safety system. Helping with the wiring issues throughout, 034 Motorsports provided an AIM MXL Pro dashboard that features both GPS and wideband integration.
Nowadays, this car is only driven once or twice a month, depending on the schedule of events it's participating in. This season, it will hopefully be joined by its new sister car, an '06 widebody STI. Having received multiple First Place wins and many other podium finishes, this '96 Impreza has certainly set the bar high. Even $80,000 later, Michael is still happy to be the proud owner of one of the most impressive race Impreza's out there. Still don't believe us? Check out driver Brian Lock putting the car through its paces on YouTube.
Cosworth 2.5L Subaru B-4
JE forged pistons (10:1 compression)
JE piston rings
ARP rod bolts
Cosworth high-capacity oil pump
Cosworth high-capacity oil pan
Cosworth windage tray with baffle plate
Setrab oil cooler core with Mocal sandwich adapter
Cosworth camshafts (duration and lift: 278-degree, 10.7mm intake; 274-degree, 10mm exhaust)
GReddy timing belt
Cosworth CNC port and hand-polished cylinder head
Cosworth valves and valvesprings
Cosworth retainers, keepers and rockers
GST Motorsports turbo kit
Garrett GT35R turbo
Blitz intercooler (24x10.4x2.67-inch)
TiAL 44mm external wastegate
TiAL 50mm atmospheric blow-off valve
GST Motorsports custom piping
K&N air filter (4-inch) with GST piping JDM Subaru intake manifold, flow-matched and rechambered by TEC Engineering
GST Motorsports 3-inch exhaust with Injen crosspipe
Bosch Motorsport 044 fuel pumps
Walbro 255lph fuel pumps
RC Engineering fuel injectors (1,000cc/min)
Aeromotive fuel pressure regulator
Hydra Nemesis engine management system
Subaru Spec C six-speed transmission (JDM)
Kartboy short shifter
ACT unsprung six-puck clutch with HD pressure plate and flywheel
Cusco clutch-type differentials
Prodrive-spec Ohlins triple adjustable shocks
Swift Springs (650-pound front, 550-pound rear)
Whiteline Automotive anti-rollbar, 27mm
Whiteline Automotive anti-lift kit
Whiteline Automotive bumpsteer correction kit
Whiteline Automotive endlinks
Cusco lateral links
Cusco trailing arms
Prodrive GC05 Wheels (18x9.5)
Rota Torque Wheels (18x 9.5)
BFGoodrich R1 Tires (275/35-18)
Stasis Engineering Alcon front discs (340mm)
Stasis Engineering Alcon front calipers (six-piston)
Stoptech Rear Discs (316mm)
Subaru/Brembo STI rear calipers (two-piston)
Stasis Engineering stainless braided brake lines
Calculated Risk front splitter
Calculated Risk front canards
Calculated Risk brake ducts
Calculated Risk rear diffuser
Calculated Risk rear diffuser
Calculated Risk flat underbody
VFiber carbon-fiber hood
VFiber carbon-fiber trunk lid
TEC Engineering side skirts
Racetech six-point harnesses
Firesafe fire system
AIM MXL Pro dash with GPS and wideband
1996 Stock Impreza (1.8 Liter)
2008 Subaru WRX sti
APR Performance 2005 Subaru Sti Widebody