In mid 2003 , Cosworth provided the 3.5 L V8 XG badged as a Chevrolet Gen 4 engine to IRL IndyCar Series teams . In mid 2003 , Cosworth provided the 3.5 L V8 XG badged as a Chevrolet Gen 4 engine to IRL IndyCar Series teams after the proprietary Chevrolet Gen 3 engine proved inadequate against rival Hondas and Toyotas during the 2003 season .