The Porsche 911 GT1 was a car designed for competition in the GT1 class of sportscar racing, which also required a street legal version for homologation purposes. The limited-production street-legal version was labeled the 911 GT1 Straßenversion (Street version).
With the revival of international sportscar racing in the mid-1990s, though the BPR Global GT Series (which then morphed in to the FIA GT Championship) Porsche expressed interest in returning to top level sportscar racing and went about developing its competitor for the GT1 category. Cars in this category were previously heavily modified versions of road cars, usually supercars such as the McLaren F1 and Ferrari F40, but when the 911 GT1 was uneveiled in 1996 Porsche had exploited the rule book to the full and stunned the sportscar fraternity. Rather than develop a race version of one of their road going models, what they created was effectively a purpose built sports-prototype, but in order to comply with regulations a street legal version was created, 911 GT1 Straßenversion - literally a road-going racing car.
In spite of its 911 moniker the car actually had very little in common with the 911 of the time, however its frontal chassis was shared with the then (993) 911, while the rear of the car was derived from the Porsche 962, including its water-cooled, twin-turbocharged and intercooled, four valve per cylinder flat-six engine which was arranged in amid-mounted position, compared to the rear-engined layout of a conventional 911. The engine was making about 600 PS (441 kW; 592 hp). In comparison, the 993 generation 911 GT2, which was otherwise the company's highest-performance vehicle, used an air-cooled engine with only two valves per cylinder.
The new vehicle was an outright success at Le Mans, winning the GT1 class at its debut race, although it lost the overall victory to Joest Racing's Porsche WSC-95 prototype, still a success in that this vehicle used a Porsche powerplant.
The 911 GT1 made its debut in the BPR Global GT Series (the FIA championship's predecessor) at the Brands Hatch 4 hours, where Hans-Joachim Stuck and Thierry Boutsen won comfortably, although they were racing as an invited entry and were thus ineligible for points. They followed up by winning at Spa and Ralph Kelleners and Emmanuel Collard triumphed for the factory team at Zhuhai.
The '96 GT1 had around 600 PS (441 kW) and was clocked at a top speed of exactly 330 km/h (205 mph) on the legendary Mulsanne Straight in the practice sessions of the 1996 Le Mans 24 Hours Race (presumably on a low downforce setup).
911 GT1 Evo
In 1997, the new Mercedes-Benz CLK-GTR was successful in the new FIA GT Championship that replaced the BPR, as it was developed for racing. Mercedes did not enter Le Mans yet with their new car, though. The Porsche did not prove to be as fast in the FIA series, and failed to win a single race, first against the McLaren F1 GTR, and then against the new CLK-GTR.
Towards the end of the 1996 season Porsche made revisions to the 911 GT1 in preparation for the 1997 season. The front end of the car was revised including new bodywork which featured headlamps that previewed the all-new 2nd generation (996) Porsche 911 which would appear in 1997. The revised car was known as the 911 GT1 Evo (or Evolution). As far as performance goes, the car had the same 600 PS (441 kW; 592 hp) turbo-charged engine, but new aerodynamics on the car allowed the '97 car to be considerably faster than the 1996 model - acceleration was better, although the top speed was still around 330 km/h (205 mph) on the La Sarthe Circuit (in the race, the GT1-Evo reached 326 km/h). However, the works cars suffered from reliability problems and did not last the full race distance; a privately entered 1996 specification GT1 managed 5th overall and third in its class, but was beaten by the BMW-backed and powered McLaren F1 GTRs.
For the 1998 season Porsche developed an all-new car, the 911 GT1-98. Designed to match the also new Toyota GT-One and Mercedes-Benz CLK-GTR, the 911 GT1-98 featured bodywork which bore more of a resemblance to traditional sports-prototypes than the previous 2 models while a new sequential gearbox was installed. As per the regulations a street-legal version of the 911 GT1-98 was spawned, but it is believed that only one variant was produced which was still sufficient to satisfy the regulations.
During the 1998 FIA International GT season the 911 GT1-98 struggled to match the pace of the Mercedes, which also were improved, with the main reason being down to the air-restrictor rules being which were regarded as unfavourable to the turbo engine (the Merecedes being naturally aspirated). The Michelin tyres of the factory team and especially the Pirelli of the private Zakspeed team were also considered inferior to the Bridgestone of Mercedes.
At the 1998 Le Mans however, it was a different story. The BMW V12 LM retired with wheel bearing trouble, and the Mercedes CLK-LM vehicles had oil pump troubles in the new V8 engines that replaced the former V12. The Toyota GT-One, which was considered to be the fastest car, also suffered gearbox reliability problems.
The 911 GT1-98, despite being slower than the Toyota or the Mercedes, fulfilled Porsche's slim hopes, taking both first and second place overall thanks to reliability, giving Porsche its record-breaking 16th overall win at Le Mans, more than any other manufacturer in history.
At Petit Le Mans race in Road Atlanta, the 911 GT1 '98 of Yannick Dalmas made a spectacular backward flip and landed rear first before hitting the side barriers, as did the BMW V12 LMR at the same race in 2000, and most infamously the Mercedes-Benz CLR at Le Mans in 1999.
The GT1 '98 was set up with higher downforce in the race than the previous two years, which reduced its race maximum speed to 310 km/h (193 mph). However, in the 1998 Le Mans 24 Hours test days, the car hit 330 km/h (205 mph) on the Mulsanne Straight on a lower downforce setup.
With Mercedes dominating FIA GT1 in 1998, all other entries including Porsche withdrew for 1999. The GT1 class was cancelled, and the FIA GT Championship was contested with GT2 cars. Porsche could have entered at Le Mans, but chose not to try to defend the win of '98 against new machines from other factories.
Champion Racing brought a 911 GT1 Evo to America to race in the American Le Mans Series, but was only allowed to do so as an LMP (Le Mans Prototypes) class entry, where it proved uncompetitive against actual prototypes such as the BMW V12 LMR.
Following Champion's purchase of a 911 GT1 Evo for 1999, Gunnar Racing offered a custom race car to the team with intentions to race in 2000. The car, known as the Gunnar G-99, was a custom-built 911 GT1 with an open cockpit. The chassis was made from scratch yet remained nearly identical to the 911 GT1 mechanically, even using the bulk of the bodyparts. A large rollbar was put over the open cockpit to help protect the driver. A 3.6 litre flat-6 from a Porsche 911 GT3 was used in place of the standard 911 GT1 unit.
However, Champion would instead turn to buying a Lola B2K/10, so the Gunnar G-99 was temporarily abandoned. The car would resurface in the Rolex Sports Car Series in 2002, yet would not be allowed to race until it had a roof again. Therefore Gunnar Racing rebuilt the car with a near identical GT1 roof, and briefly competed in 2003. The car would take a best finish of second in class twice before being retired due to lack of funding.
Regulations for the GT1 category stipulated that to be eligible, a total of 25 cars must be built for road use. Porsche developed a fully road-legal version, dubbed "911 GT1 Straßenversion", and delivered one in early 1996 to the German government for compliance testing, which it passed. The engine had to be slightly de-tuned to meet European emissions laws, although its 544 PS (400 kW; 537 hp) and dry weight of 1,150 kg (2,535 lb) proved to be more than adequate; the vehicle could accelerate to 100 km/h (62 mph) from a standstill in 3.9 seconds on its way to a top speed of 308 km/h (191 mph).