How does an aftermarket tach hook up on a 1990 Rx-7? I've heard that you just put the selector switch on the back on 4cylinder and put the input wire of the new tach on one of the coils. How EXACTLY do you do all of this. I'm asking because I want to buy a Proform shift light from Jeg's. The light is unique because it requires no ignitions boxes or seperately purchased rpm "pills", it simply has a dial on the back which lets you choose a shift point between 3,000 and 11,000 rpms. It hooks up just like an aftermarket tach with the green, red, black, and white wires. Any help on this would be helpful!

 

theres a wire coming off the coil closest to the front of the car that isn't plugged into anything (just a wire with a female connector). go buy a male crimp plug and put it on the green wire.

 

if you use the front coil your rpm's will be twice as high... you need to go off the trailing coil near the firewall I think.