if it has hub caps its an S (SOHC non-VTEC)
if it has stock rims its either an Si (SOHC VTEC) or a VTEC (DOHC VTEC)
if it has rear disk brakes its either an Si or a VTEC
if you can see the tachometer look at the redline... S = 6800, Si = 7200, VTEC = 8200