In mid 2003, Cosworth provided the 3.5L V8 XG badged as a Chevrolet Gen 4 engine to IRL IndyCar Series teams. The XG finished 2nd in its first race at Michigan on 27 July 2003. Sam Hornish, Jr. went on to win 3 races that season with the new XG. The XG was reduced in size to 3L for 2004 season. It won one race in 2005 during Chevrolet's final season in IRL.