anyone know how to hook up shift light to a rb20det into 240sx?
Hook it up to the ECU rpm signal. Just get a wiring diagram for your ecu. Its really simple.
Or
Pull out the speedo and get a multimeter to the wires in the back of a working tach (if you have one). Just rev the car and watch for a change in the multimeter read out. Hook into that wire.
cant you run it off the coil pack?
Yes.
Pick one of the coil packs and choose the wire that is not the same on all the Coil Packs.
eg. If all 6 have a Red and a Blue and the third one is different from the rest then most likly that’s a useable Tach Signal.
Same goes with Injectors, you can use the odd wire out from Injectors.
Keep in mind this is usually on Nissans it’s a (-) pulse so make sure your Shift Light Accepts a (-) pulse.