There are easier ways for those that don't posess the equipment or know-how to re-map an ECU.
Found this kicking around on the interwebs (Does not require any ECU or ignitor mods):
After market coils for CA18DE-T multicoil (U12, S13)
N/A for U11 motor unless later model ECU and loom from s13 or U12 is upgraded as well.
Parts: (stuff to buy)
4 X Bosch coils HEC-715/6 (diffence in lead connector on coil, male/female) about $40 - $60 per coil
1 X Custom lead set, about $120 - $150 for a decent 10mm set.
1 x Bracket to mount coils - can be any $ depending on who you know and how fancy it is, ie: mine was
free, but i had to drill holes myself, material and bending was free.
8 x Female spade connectors (larger size of the two available) for wiring - $5
1 x 6 pack of fav alchol
Tools: (stuff to borrow)
wire strippers
crimpers / wire cutters
Intructions:
First thing would be to get your bracket made up for mounting the coils onto, and also while the car
is still running with the stock setup, take it to your local leads place, and show them where your
coilswill be sitting so they can make up/give you the correct length set for your application and
still drive your car home. This way you will have all you parts ready to go and knock the job over
all at once.
Disconnect the negative terminal on the battery. Take the coil cover off of your motor, 8 bolts
10mm/phillips (NB: If you have your top mount still installed remove this first, which is pretty
straight forward, just look for the bolts and clamps holding it on). Begind drinking your 6 pack. Disconnect the wiring from
each coil marking each plug/connector as you go with a number corresponding to which coil you pulled
it off of - number 1 is closest to the timing belt (drivers side/right side) and continues upto 4
consecutively to the other end.
Sell your stock coils to someone along with all the bracketing. Mark each of your new coils with
numbers from 1 to 4. You should probably have your coils mounted on your bracketing system and worked
out where the bracket will sit in your engine bay by this stage so you can work out how long your new
leads will have to be, and also how short you can cut the old wiring to hook up to your new coils, or
even how far you have to extend your wiring depending on where you decide to put the coils, closer to
the plugs is prolly better for tidyness, not on top, just close.
The new coils will only have a + and -, where as the old factory coils had three
wires. The thin black wire can be disgarded completely, follow where it goes and remove it. The
thick yellow one is constant remote power (+) which is a common for the coils and the pink one is
the trigger/negative (-) which has an INDIVIDUAL signal for each coil. Connect each yellow wire
to each coil on the + terminal, and the pink TO THE CORRESPONDING coil - ie: when you disconnected
the wiring connectors/plugs from the stock coils and marked them with numbers, connect the pink wire
from the connector marked (1) to the aftermarket coil you have marked (1) onto the (-) terminal and
repeat so on until (4). * When you cut the each of the wires from the standard plugs, strip the end of
the wire, and crimp one of your spade connectors onto the wire, then plug it onto the correct terminal
on the coil. Don't cut all the wires from all of the standard plugs at once, or you won't know which
is which, just cut one wire at a time and connect it the the correct coil straight away to avoid \
confusion later on, especially if you enjoying a few rumbos while you work Tape up all your wiring
etc, tidy it up, put condue on it if you like, make it look pretty.
Plug the leads onto your coils and then to your spark pulgs, once again marking sure the lead coming
from your new aftermarket coil marked (1) is going to number (1) spark plug, which once again is the
one closest to the timing belt/drivers side of the motor. Repeating up until number (4) continuing
to the right sequentially.