9ff

9ff is a German car tuning company, based in Dortmund, founded by Jan Fatthauer in 2001, specializing in converting stock Porsches into street legal racing machines, either as fully tuned cars, or selling individual parts or kits.

Jan Fatthauer founded 9ff Fahrzeugtechnik GmbH in 2001 in Dortmund, Germany, as a Porsche tuning company. Fatthauer earned a degree in automotive engineering, and had worked at recognized tuners until 2001.

In May 2004, 9ff achieved its first record, reaching 372 km/h (231 mph) with a 9ff T6 on the Nardo Ring race track in Nardo, Italy. The company claimed that they had the "fastest Porsche in Nardo". In December of that year, Fatthauer drove a new car, the 9ff V400, up to 388 km/h (241 mph). This car held the record for the world's fastest car until the company beat that record with the GT9 later that year. At the time, 9ff was building a wide variety of products, including some powered by alternative fuel, setting several records.

In September 2006, the 9ff TRC-85 reached 380.5 km/h (236.4 mph), becoming the fastest street-legal convertible of its time.

In October 2008, the 9ff CT78, based on the Porsche Cayman, won the top-speed record for cars powered by alternative fuel, with its top speed of 347 km/h (216 mph), powered by bioethanol.

On April 10, 2008, the 9ff GT9 reached 407 km/h (253 mph) (confirmed with GPS), becoming the fastest street-legal car in the world.