individual coil signal to tach :( Options

[match220]

my setup
gen III 3sgte with autronic ecu + individual audi 1.8t coils (the stable year versions). Each coil has its own built in igniter and 4 pins: positive from switched connection, signal ground, ecu signal, and power ground. And the coils are TCI coils, not CDI, not that it matters. I'm getting tired of not having a tach signal so I'm hoping you guys can help me figure something out aside from running 4 diodes in-line with the signal ground and jumping off one of the coils to run to the tach.

1mz tach
I was hoping I could read up on how it was done on the 1mz swap which has a 3 coil wasted spark setup, nada..the 1mz swap just requires the gauge clusters to be disassembled and mixed together to work.

mixing audi and toyota gauges
My initial plan was to mix the audi gauges with the celica gauges and use the tachometer output from my autronic as the tacho signal, not going to work unless I recreate the circuit-board for the audi and wire it into my celica. I bought the gauges off of the same kind of car the coils came off of, but they are all driven by a signal from the ecu it looks like, not to mention it's just one big circuitboard.

running only audi gauges
I've also thought about running the audi gauges instead of my celica gauges, BUT I would have to wire me speed sensor and fuel level sensor into the autronic and run outputs to the gauges.

using a tach adapter
Now I'm wanting to run the tach signal off of the autronic to the celica gauges. Is there an adapter I can buy? I can configure the autronic to run a normal tach output or invert the output to the tach as either a .5 msec pulse or 1 msec pulse, nothing else.

[Hafkai]

There is a quite easy way to get our stock tach working with most aftermarket ECU signals. You just have to take out your tach and take a look at the circuit board, there is a ~43kohm resistor between the signal input and the IC that controls the tach. I never measured the voltage spike that is coming from the stock ignition so i dont exactly know what the voltage the IC receives should be but i tried some resistors and the tach was ok with a 1kohm resistor instead of the 43kohm.

While i was playing i checked what kind of signals the tach could handle, well the IC seems to be happy with everything, PWM from 1-99%, sinus, saw, triangle and of course square, so every aftermarket ECU should work.

Since my ECU pulls the tach signal to ground i had to put a pull up resistor (~500ohm) between 12V+ and the tach signal cable. Seems to work flawless on my tach.

I can upload a pic of the resistors later.

[match220]

There is a quite easy way to get our stock tach working with most aftermarket ECU signals. You just have to take out your tach and take a look at the circuit board, there is a ~43kohm resistor between the signal input and the IC that controls the tach. I never measured the voltage spike that is coming from the stock ignition so i dont exactly know what the voltage the IC receives should be but i tried some resistors and the tach was ok with a 1kohm resistor instead of the 43kohm.

While i was playing i checked what kind of signals the tach could handle, well the IC seems to be happy with everything, PWM from 1-99%, sinus, saw, triangle and of course square, so every aftermarket ECU should work.

Since my ECU pulls the tach signal to ground i had to put a pull up resistor (~500ohm) between 12V+ and the tach signal cable. Seems to work flawless on my tach.

I can upload a pic of the resistors later.

I've only had the tach barely jumping since I have finished the engine. Today if I have time I will take out the gauges and look for the problem if I can find it.