AggieDave

I have the 89-91 stock TII computer and i need to know which wire is the tach send wire that goes to the computer. I am wiring up a rebic that i have and dont know what wire on the stock harness to tap into.

Thanx in advance

dave
87 TII ( Series V Conversion)

Icemark

There isn't one at the ECU.

You need to go to the trailing coil or the back of the cluster and use the yel/blue there.

AggieDave

yes there is. that would retarded if there was not. how else would the ecu calculated timing and all that other stuff...

i found it. i just hooked into the rpm wire for the AVC-R that i have. i had to get a diagram from the apex-i website.

it is the purple wire for those that might need the info

dave

Icemark

The ECU gets its engine speed signal from the CAS, it is not an accurate tach signal.

The tach signal (what everything that uses tach in the car- like the cluster, the cruise, the power steering, etc) is picked up off the trailing coil. It is a buffered signal specific to be a tach wire (yel/blu). It does not go to the ECU.

Furthermore there is no purple wire going into the ECU... so I don't know even what you tapped into and could be damaging hooking up an unbuffered wire too.

Piranha

Ah... so thats why my tach on my turbo timer is off a little bit.

AggieDave

the purple wire is the tach signal for the AVC-r. is this goin to be a problem if i tap into there? or should i run a wire to the coil. if so where on the coil do i hook it up?

dave

Icemark

were's the purple wire hooked too???

AggieDave

the purple wire is hooked up to the ecu. go to apex-i's web site and they have diagrams for each car as to where each of the wires are located on the facotry harness.

since the boost controller is hooked up to the ecu i want the injector controller to work (rpm dependant variable) the same way.

i called the guys at greddy and they aggreed with this method. but i am sure that there are many other ways to do it.


dave

Icemark

Without you saying the wire color, I can't not say if it is okay to use.

The problem is often people will tap into a wire or a couple of wires with a sense circuit and it will overload the controlling transister... suddenly an injector is always on, or timing is advanced 20 degrees, or countless other problems. Or if the wire is shorted by a poor unprotected wire run then a whole array could be lost in the ECU.

But either way, You asked for the tach wire, I gave the Mazda approved wire, used for countless remote starts, tachs, cruise controls, etc. if you chose to use another wire it will be your problem.