With the return of internationals sports car racing in the mid-1990s, Porsche decided to develop an entry for the GT1 category, originally intended for manufacturers to showcase their 'Supercars.' Úp until then, cars competing in the category were heavily modified versions of road going McLaren F1s and Ferrari F40s. But when the 911 GT1 was unveiled in 1966 it became obvious that Porsche had once again taken advantage of the rule book, extracting every advantage possible. What had been developed was not a race version of the 911, but what was effectively a purpose built sports prototype with a little 911 thrown in.
Despite being called a 911, the car had little in common with the 911 of the time. The front clip did come from the production 911, while the rear of the car was essentially a Porsche 962, including its water-cooled, twin-turbocharged and intercooled, four valves per cylinder flat-six engine, which put out about 630 horsepower.
The 911 GT1 and its successor, the 911 GT1 Evo, while achieving a modicum of success both in Europe and North America, never achieved its primary goal - an overall win at Le Mans. Porsche did take the overall victory at LeMans in 1966 and 97 with Joest Racing who was running the Porsche powered WSC-95 prototypes.
For the 1998 season Porsche developed an all-new car, the 911 GT1-98. New GT1 rules stipulated that cars could be built from scratch and homologated if a road going version was also made available for sale. The ante had also been raised by the addition of the Toyota GT-One and a new Mercedes-Benz CLK-GTR.
The 911 GT1-98 featured bodywork which looked even more like a traditional sports prototype than the previous GT1s. During the 1998 FIA International GT season, the 911 GT1-98 struggled to match the pace of the Mercedes which had also been revamped and improved. The new rules also favored normal led aspirated engine powered cars and handicapped turbo engines.
At Le Mans, however, it was a different story. The BMW V12 LMs retired, as did the Mercedes CLK-LMs. The Toyota GT-One, which was the fastest of them all, suffered gearbox failure.
The 911 GT1-98, despite being down on power to both the Toyota and Mercedes, more than fulfilled Porsche's hopes by finishing one - two overall thanks to its reliability and consistency. This gave Porsche its record breaking 16th overall win at Le Mans, more than any other manufacturer in history.Source - Porsche