My friend used to be a student of Sardar Patel College of Engineering, Mumbai. According to her, the answer to your question depends on a lot of factors. They can be your category of reservation and the branch you aspire to pursue.

If you want to have chances of being considered for admission, your percentage should be above 90%. The cutoff changes every year, though.

My friend got admission in the second year after her diploma percentage was 90%. She was in the OBC category. For getting admission in the SPCE for the electrical stream without any reservations, securing a percentage of 88% to 89% in your diploma course in your final year is mandatory.