Jan Nilsson is most famous for his appearances in the Swedish Touring Car Championship, having appeared in eleven seasons, winning the championship twice and taking 30 race wins.
Jan Nilsson started competing in Formula Ford in 1983 before moving on to Formula 3. He became the Swedish F3 champion in 1989 and drove Formula 3 in Japan, Mexico and USA before moving to Clio Cup Scandinavia. He finished second in 1992 and moved up to Renault Spider Eurocup in 1993 after becoming champion in 1992. His first year in the Spider Eurocup brought him fourth place, as did the 1995 season. In 1996 he was third, and the very same year he was the main force behind the creation of the Swedish Touring Car Championship.
Jan Nilsson's own team, Flash Engineering, became the official Volvo team. He took the title in 1996 and 1997, both in a Volvo 850. and was second in 1998, this time in a Volvo S40. In 1999 he was 5th, and 6th in 2000. Some critics meant that he had lost his pace, but he proved them wrong with becoming second overall in the 2001, 2002 and 2003 seasons.
After a somewhat tough 2004 season (only one race win during the whole season) Jan Nilsson sold Flash Engineering. The team changed it's name to Polestar Racing. Jan Nilsson started a new, smaller team from scratch for the 2005 season, also called Flash Engineering. The team ran one BMW 320i with Jan Nilsson as the only driver. He finished 9th overall.
Flash Engineering signed on several new sponsors for 2006 and dramatically increased their available funds. They also signed on double Swedish champion Richard Göransson and former Flash Engineering Volvo driver Edward Sandström. Göransson and Nilsson drove new BMW 320si cars for the 2006 season, while Sandström drove the BMW 320i. Richard Göransson finished second in the championship while Nilsson was 9th again.
In 2005 Jan Nilsson aslo raced in the Scandinavian Porsche Carrera Cup that runs as a support class to STCC. This meant that Nilsson did four races each weekend, two in the BMW and two in the Porsche! Luckily for him both cars were rear wheel drive. Nilsson had more success in Carrera Cup and finished third overall. For 2006 he focused on STCC and his spot was filled by reigning champion Fredrik Ros.