The careful approach to gas flow continues throughout, from the WRC S10 inlet manifold and K&N air filter with 100mm inlet and polished stainless steel one-piece Nimonic inlet valves, to the 72mm throttle body (to feed the hungry engine when Clark gathers the nerve to push the loud pedal all the way down). A high-flow intercooler with a twin-tube core and 70mm stainless steel pipework complete the picture. Keeping a lid on all the madness is the V4 STI cylinder head.
To cope with the force of nature that is Gobstopper on a charge, everything is bulked up, everywhere. The team installed proprietary extreme Arrow connecting rods, a 75mm steel crankshaft, new coated flat-top Omega pistons, upgraded valve springs, plasma nitride-treated titanium spring caps, WRC-spec main and big end bearings, a WRC R-profile timing belt system, and more. Despite all this, RCMS claims a relatively lightweight compression ratio of 9.5:1.
Even more impressive than the final spec, though, is the fit and finish. Many high-power Imprezas look like the engine has blown before they turn a wheel, with rough seams, loose wires and ill thought-out layouts requiring quick fixes at any moment. This engine bay looks so clean, so perfect, that it could have emerged from Prodrive's factory after years of development.
Providing enough 120-octane race fuel to keep this beast awake is a science in itself. It starts with a 6.8-gallon (26-liter) rubber-Kevlar bag tank in the trunk. Two Bosch 200lph pumps feed it forward into the RCMS distribution block set into the sides of the WRC magnesium reverse inlet manifold. This manifold has an epic eight gold-plated 750cc injectors to ram in the pressurized juice from twin SX 4.0 bar fuel regulators. This car wouldn't get you between Starbucks, let alone gas stations, but then it's built for a hot lap and nothing more.
A sequential transmission (controlled by paddle-shifts or that giant lever erupting from the floor) takes just 0.05 seconds to switch cogs. That's twice as fast as the much-vaunted F1-Superfast system on the Ferrari 599 GTB Fiorano. A Subaru six-speed casing has been modified to take the Group N Modena dog-tooth sequential.
There's a plated center diff, plated front Modena differential and a near-indestructible triple-plate, alloy-covered OS Giken clutch kit. Don't forget the new rear axle, from an STI R180 with 3.91:1 crown wheel and pinion, plus a lightweight yet super-strong flywheel. Rally-spec driveshafts and a carbon fiber propshaft are also deployed to prevent the drivetrain shredding itself all over the road.
All non-essential gear has been ditched in the quest for less weight. That goes right down to a plastic rear window and lightweight battery in a custom-made cradle fitted just below the glovebox--so the cable to the starter motor could be shorter. Apart from the long sequential gear lever (with hydraulic handbrake attached), single-piece WRC-spec steering column, plus a huge number of dials and switches on the Motec dash (covering everything from the fuel pump to a manual override for the nitrous oxide), there is nothing else to clutter the cockpit. It all adds up to just 2460 pounds, despite the cage and beefed-up componentry. It's as light as physics will allow.
Work on the chassis involves heim-jointed rear lateral links, rear trailing links and upright bushes. The car also gets polished aluminum front arms, plus EXE-TC fully adjustable dampers with remote reservoirs, which also feature high- and low-speed bump and rebound adjustment. If the name sounds familiar it should, EXE-TC designed the suspension for WRC Imprezas. Gobstopper has the tarmac-spec set-up, with adjustable coilover springs for ultimate tweak-ability. Keeping the wheels on the floor at all times is the hardest job at high speeds; losing traction at one corner for a fraction of a second can lose the race at best. At worst, it can hurt--a lot.
Those 19x8 wheels are Speedlines and they're surprisingly restrained for general track use, using 225/40R19 Pirelli P Zero Corsa tires. Even here there's high technology: the hubs are fitted with speed sensors to monitor wheel slip and feed vital information back to the traction control system. And when he goes drag racing, Clark has a whole new world of grip available from 15x8 wheels dressed in much taller rubber.
Since the car is destined primarily for the drag strip, there's no reason to go for anything beyond steel brakes, although they're looking at ceramic upgrades for the circuit-based Time Attack series that Clark will assault this season. For now, Gobstopper's stoppers are vented, steel AP Racing 355mm front discs mated to six-piston calipers, due to the level of feel and the fact that ceramic stoppers take time to heat up. He uses the elliptical-groove 290mm floating numbers on the rear with four-pot calipers and is happy with the final balance.
Few would bet against this almighty creation taking a hatful of records and redefining the word quick when it comes to the Impreza. After a few competitive outings, they might even stop laughing at the name when rivals realize that this is a car capable of breaking jaws.