BEIJING, Aug 18 (Reuters) - China has designated eight cities as automobile export zones, the official China Daily reported on Friday, part of a bid to help its domestic car makers push for overseas sales to maintain their rapid growth. The cities, named by Commerce Minister Bo Xilai at a Beijing ceremony, are the coastal ports of Shanghai, Tianjin, Xiamen and Taizhou, the Yangtze river cities of Wuhan, Wuhu and Chongqing and northeastern Changchun, the newspaper said.