[40flash]

OK. One more time,this time from experience....
I now have my stock S14 tach working perfectly with the Dakota Digital SGI-8D. Here is how you hook it up. It's really easy.
1. Any switched on with ignition 12V + to power in.
2. Run a ground to the ground input, DUH!
3. Signal in. Tap into, (don't cut) the yellow/red wire that feeds the number 1 cylinder coil wire. It feeds a ground signal from the ECU terminal 62 to the number 1 coil.
(side note) I tried the injector wire for the number 1 cylinder and it works but when you let off of the gas, the ECU shuts off the injector for a few seconds as you decellerate which interupts the tach signal for tha period of time and the tach shuts off until the injector gets turned on again. Trust me. Use the coil wire. No issues.
4. Output wire from the dakota Digital box to the tach. At the 240SX F3 plug there is a tach siganl wire that by coincidence is also Yellow/red (F3 terminal 26.) Plug this wire into the output 2 terninal.
Wiring is done.
5. there are 4 switches on the Dakota Digital box.
A. Switch 1, on.
B. Switch 2, off
C. Switch 3, on.
D. Switch 4, off
You're done. Drive it.

I'm also using a SGI-5C Dakota Digital box for the S14 stock speedo. It's hooked up to the ABS sensor in my Q45 diff with 3.54 ring & pinion and S15 helical limited slip. Their customer service is great. There are several different way to hook up their box and get your speedo working including their magnetic sensor on your drive line if you don't have a diff with a speed sensor. Buy the box and call them. They will walk you through the set-up over the phone.