Apart from the obviously expensive interior work, the T5 shell has been the subject of extensive re-engineering to convert it from a front-engine, front-drive configuration to accept the rear-engine, rear-drive Porsche 996 GT2 drivetrain and some Porsche suspension elements.
Unlike both the stock T5 and the GT2, the TH2 uses air springs made by a Dutch company, coupled to H&R dampers and a ride-height lift system. The ECU lowers the ride height in two steps for better handling and aerodynamics.
For Nardo, TH recalibrated the suspension ECU to lower the front end by 30mm over 220 km/h (136 mph). This reflex camber setting reduces lift over the front axle as well as drag.
The basic engine is 996 GT2, tuned by 9ff to the same spec as the motor in the 9ff 9f-T6 that ran to 372.2 km/h (232.7 mph) at Nardo in 2004. Back then, this engine made around 750 hp at 6590 rpm with 622 lb-ft of torque at 6000 rpm, but the TH2 has a more advanced camshaft grind and some other small mods to up the big numbers to 800 hp and 664 lb-ft of torque.
9ff's Jan Fatthauer explained that his team built the engine for TH Automobile, where it was installed. The vehicle was then returned to 9ff for a custom exhaust system and ECU mapping.
The gearbox is GT2 with an uprated clutch, and a dual mass flywheel to retain comfort. Fifth (0.85) and sixth (0.71) ratios are very high for top speed and economical cruise. However, like the previous generation Corvette, sixth is so tall that top speed is reached in fifth. Stopping power comes from big brakes, 390mm discs with six-pot calipers in front and 365mm discs with four-pot calipers at the rear.
"The radically different vehicle weights and gear ratios meant a unique program for the ECU," Fatthauer explains. "Also, TH's bespoke water and air-cooled intercoolers do a good job of lowering intake temperatures, but have a bit more back-pressure than ours. Because of this we had to run 1.4 rather than 1.3 bar boost for the same power. The turbochargers are our KKK hybrids that are built from a combination of K24, 26 and 29 parts and are a 9ff exclusive." Because the T5 is almost 900 pounds heavier than the GT2, it needs more torque low down, but with 1.4 bar of boost tuned to deliver 900-920Nm, this isn't really a problem.
Despite its blunt shape, the TH2 exceeded all expectations at Nardo and screamed around the banking at 194.2 mph. That's 1.19 mph faster than the latest 997 Turbo.
The next step in TH Automobile's journey to build the ultimate VW bus will be 4WD. The choice is between using 996 Turbo running gear or splicing the Porsche power train with VW's Synchro AWD system. Watch this space!
9ff TR1000-top-speed king
9ff has won the Nardo top-speed shootout three times with various modified 911s. On top of that, in April 2008 the 987-hp 9ff GT9 achieved 255 mph at the Papenburg high-speed test track in northern Germany.
Compared to the handcrafted GT9, the black TR1000 that 9ff brought to Nardo this year looked positively tame. If not for its distinctive 9ff alloys, most people would have thought it was a near-stock 997 Turbo.
Although it posted an impressive enough top speed to win the event by a significant margin, the TR1000 suffered from an unforeseen electronic gremlin that stopped it from going even faster.
This was the first 997-based car 9ff has ever built to take part in a top-speed event, and due to the late arrival of some components from suppliers, the car was brought straight to Nardo with no prior opportunity for testing.
On his flying lap, Jan Fatthauer discovered that the TR1000 simply would go no faster than 375 km/h, or 233 mph, officially clocked by the independent timing crew and his own on-board GPS-based timing gear.
Subsequent diagnostic interrogation of the ECU revealed that the Porsche PSM system simply could not accept that the car was doing that speed, and refused to allow it to go any faster.