Top 100-150 rank students generally don't come as many of them have already cleared JEE.
And after that the seats in AEC gets filled up in this order & the no. Of  seats provided in the bracket -
1. Mechanical (60)
2. Civil (90)
3. Cs (20)
4. Electrical (90)
5. Electronics (60)
6. Chemical (60)
7. Industrial production  (20)
8. Instrumentation  (20)
Hope this helps..
Best wishes...