Jee Mains and BITSAT are two completely different exams conducted for two different set of colleges, from jee mains you'll get admissions into NITs and other colleges that take admissions thorugh jee mains while to get admission into BITS you need to clear it's enterence exam that is BITSAT though 170 marks in jee mains isn't a bad score but if you want to get BITS you need to clear BITSAT that's the only option available till now.

Good Luck!!.