MRT to Novena transfer 56, 57, 166, 851, 980. (35 - 40
minutes)
Straight 57 --> 40 - 45 minutes
Straight 56 --> 45 - 50 minutes
All of them includes waiting time.
(Alight the next stop after Little India MRT and crossover to the
other side of the road.)
I always use this: http://gothere.sg/maps#q:bishan%20mrt%20to%20sim%20lim%20square
Apparently the MRT+Bus Junyang provided is fast enough, 28
minutes journey time.
Edit the time and date of travel at gothere.sg for more detailed
info.