Cosworth designed a series of replacements for the DFS to be used in IndyCar and Champ Car racing: the X-series, beginning in 1992 with the XB. The XF was developed for the 2000 season to replace the XD, and was chosen as the spec engine for the Champ Car World Series in 2003. The most recent derivative of the XF, the XFE quad-cam 90° V8 overhead camshaft, continued in that role through the 2007 season. The Champ Car World Series imposed a rev limit of 12,000 rpm down from the over 15,000 rpm of 2002. The 2004 model of the XFE had a rated power of nominal at 1,054 mmHg (intake boost pressure), and a maximum power of at 1130 mmHg (during Push-to-Pass). The 2004 XFE maximum speed was 12,000 rpm (rev limited) and torque of . The aluminium and iron turbo housing ran a boost of 5.9 psi at sea level (= boost of 12 inches of mercury which is 41.5 inches of mercury absolute). The Methanol-fuelled engine used a steel crankshaft and aluminium alloy pistons. Weight was and length was .