"On our production cars, we use the GT3 front up to the A-pillars, and build up the rest of the car using a steel tubular frame, with the body panels in carbon composite," he explains. A very "strong but light carbon-Kevlar tube in the doors provides side impact protection, and when the door is closed, this forms a rigid structure joining the A- and B-pillar elements of the built-in rollcage."
For more stability and progressive handling at speed, the wheelbase is extended 30cm over that of the GT3. The 2,923-pound GT9 is also significantly lower than the GT3, and has a flat bottom with a rear diffuser. In fact, as so many Porsches, Ferraris and Lamborghinis now have lightweight carbon-fiber race seats, the only real giveaway to this car’s serious intent is the racecar MoTeC LCD instrument display and the bespoke lightweight steering wheel with green and red buttons to control the sequential up and down shifting of the heavily strengthened GT3 six-speed manual gearbox. To work the correct way in this mid-engine configuration, the gearbox has to be inverted and placed behind the engine.
In between the engine and gearbox is the unique compound organic clutch unit. Using two organic clutch plates bolted to a steel center, it solves the age-old dilemma of combining the strength of a sintered racing clutch with the lightness and progression of an organic one. A Drexler limited-slip differential is fitted to optimize traction. Like many 9ff cars, the manual shifter is equipped with the Cartronic SQS-G (Sequential Shifting System). But instead of using a sequential shift lever on the floor like on the 911-based cars, 9ff came up with an in-house electro-hydraulic actuation system for the mid-engined GT9.
In fact, you can have one of three different types of gearbox on the GT9-R: six-speed manual, six-speed sequential and five-speed Tiptronic. We can’t imagine though, that any serious driver would opt for the old Tiptronic slush box, which is only available in combination with the least powerful 750-hp engine option. The Stage 2 engine tune is 987 hp as per the GT9 prototype, with a new pinnacle of 1,120 hp as the ultimate Stage 3. The extra 133 hp takes the GT9-R to 260 mph, with 0-186 mph covered in just 14.9 seconds. Despite the potential traction issues of rear-wheel-drive only, the claimed 0-62 and 0-124 mph times are 2.9 and 7.4 seconds respectively.
Fatthauer explained that the engine is easily upgradeable from Stage 2 to 3, so that an owner can get used to the 987 hp before coming back for more. This does not apply to Stage 1 however, as this is a 9ff modified version of the factory GT1-block-based 997 Turbo 3.6-liter Variocam Plus engine rather than the highly modified 4.0-liter used in the GT9 Stage 2 and 3 motors.
For this, the 3.6-liter Porsche GT1-based flat-six is taken out to 4.0 liters with a bespoke steel crank, titanium connecting rods, larger-diameter barrels and forged pistons. Cylinder head gas flow work and bespoke camshafts with solid lifters optimize the top-end for life at high revs.
"Our high-revving biturbo engines require as much under-piston cooling as possible," says Fatthauer, "so we use the GT3 variant of the GT1 block, which has a dual oil-spray system for cooling the underside of the pistons. The lower-revving 997 Turbo 3.6 variant of this block only has a single oil sprayer per cylinder."
The intake and exhaust systems are also bespoke for this engine, with the Garrett-based turbochargers modified in-house to suit. The ultra-efficient 130mm (OE: 70mm) thick intercoolers have double the cooling capacity of the factory Turbo ones, and their unique housing design further improves air throughput for even greater efficiency.
Built for high revs, this motor produces its 1,120 hp from 6400 to 7600 rpm, and has another 200 rpm of headroom before the electronic rev limiter in the specially mapped ECU calls a halt to the proceedings.
The 840 lb-ft of torque is simply stupendous for any road legal motor, let alone a mere 4.0-liter six-cylinder. Equally impressive is the fact that peak torque is sustained on a plateau from 5300 to 7500 rpm, delivering mind-numbing performance in a car weighing less than 3,000 pounds.
The front suspension is by MacPherson struts with coilovers, while the rear uses a five-link design with race-style pushrod actuated coilovers. This bespoke suspension, which uses H&R springs and JRZ dampers with external fluid reservoirs, has an adjustable antiroll bar at each end. All the suspension arms and top mounts have Uniball joints.
The 9ff forged alloys are 8.5- and 11.5x19-inch with 235/35ZR19 and 325/30ZR19 rubber. For top-speed runs, these are Continental SportContact Vmax tires, with Michelin Cup tires the road and track day alternative. The massive Brembo brakes use 380/350mm cross-drilled discs clamped by six-pot monoblock calipers.
It is very unusual for a turbocharged motor to rev this high and this freely, but with even bigger turbos than the original GT9 in this 1,120-hp Stage 3 version, I could feel the difference immediately the first time I opened the taps fully.
While it is easy to say that the acceleration is awesome, in the midst of all the furious noise and g-force, you realize that the power is also delivered very smoothly and progressively. Apart from making the car more user-friendly, this characteristic mitigates the stress on the drivetrain and chassis despite the huge horsepower and torque numbers involved. Where the Bugatti Veyron impresses you with its sheer speed and overall competence, it can feel aloof and remote at times, as if the breathtaking abilities of its engineering are shielding you from the pure physics.