There is no difference in pronunciation. There is no difference between the pronunciation of "Y" and "I" in Chinese Pinyin, but "Y" is neither an initial nor a vowel. According to the provisions of the Chinese Pinyin Scheme, when there is no initial in front, only the vowels in column I are written as yi (meaning), ya (elegance), ye (leaf), yao (Yao), you (worry), yan (smoke), yin (cause), yɑng (middle) and ying (English).