Is s14 is faster than s13?

No Differences. s13 (1989-1994) and s14 (1995-1997?) just explains the chassis code. Through 1989 and 1997 the 240sx use a KA24DE motor. However, the 1989/1990 KA's were SOHC and the 1991+ were DOHC, so the only faster engines would be the 1991+ 240s compared to the 1989/1990