He also co-drove a Porsche 956 with Henri Pescarolo and Stefan Johansson in the 1000km NÃ 1\/4 rburgring race . He also raced in a race to celebrate the opening of the new NÃ 1\/4 rburgring . Senna also raced in two high-profile non-Formula One races in 1984 : The ADAC 1000 km NÃ 1\/4 rburgring where , alongside Henri Pescarolo and Stefan Johansson , he co-drove a Joest Racing Porsche 956 to finish 8th , as well as an exhibition race to celebrate the opening of the new NÃ 1\/4 rburgring , which was attended by several Formula 1 drivers , each driving identical Mercedes 190E 2.3 â `` 16 .