One of the most successful and longest-lived projects of Cosworth has been its CART / Champ Car engine programme. In 1975; Cosworth developed the DFX, by destroking the engine to and adding a turbocharger, the DFX became the standard engine to run in IndyCar racing, ending the reign of the Offenhauser, and maintaining that position until the late 1980s. Ford backed Cosworth with creating a new interim design for IndyCar racing in the late 1980s, the DFS, which merged DFR technology into the ageing DFX design, but it was eventually rendered obsolete by advancing technology.