Wiring diagram interpretation

[thegreatestben]

I'm trying to figure out how to get the mitsi ignitor I've got works in terms of the output to the tacho.
I've got the factory diagram:


I took it to an auto sparky to just check my theory before trying it and killing things.
I assume that diagram is suggesting that I need to put 5v into the pin no.4 (which is labled tac on the ignitor)
He seemed to think this was odd. I was wondering if any of you chaps knew?

I've tried hooking the factory tacho wire from the car loom straight to the ignitor and it doesn't even move.

[matt dunn]

I think you are using the same EVO type igniter that I use.

You do not have to apply 5V power anywhere?
Mine is mounted way under the dash but from memory the pins are,

IB1 is signal from ECU
IB2 Is signal from ECU
OC1 Is output to coil 1
OC2 is ouput to coil 2
E is earth
VB is full 12V ignition power
Tac is tacho output.

The igniter will work without the VB wire powered up,
but the tacho output feature will not.

I run mine like that, and the tac wire goes directly to my VDO rev counter,
and is works fine,
no pull up resistors or anything else fitted and no 5V feed anywhere?.

[thegreatestben]

tach was working fine prior to switch to wasted spark.
Got nothing from a scope either

[thegreatestben]

I'm pretty certain I established I have 12v at VB as well

[matt dunn]

tach was working fine prior to switch to wasted spark.
Got nothing from a scope either

When you switched to wasted spark you must have also switched the igniter. Are you trying to run a standard factory Toyota tacho off the mitsi tac signal?

[thegreatestben]

Yeah, using mitsi coils and ignitor.
Just trying to say that it's not a probably with the tach being busted.

Might just try this:

[matt dunn]

Yeah might be wired up and working good,
but a comapatability issue with the toyota tacho and the mitsi signal.

[sergei]

Ok, judging by diagramm do not suply 5V directly.
It is the output to the tacho (which gives square wave out).
The problem you are facing is that you will need to implement resistor/diode network to emulate what is going on when it is used normally.

If you supply 5V you will burn out the transistor.
You can supply 5V via say 1k resistor, which theoretically will be sufficient. Transistor in question pulls down.

EDIT: also said tacho output is ~5V, while I believe toyota Tacho needs 12V. You could wire that 1k resistor to 12V to achieve needed output.

[ChaosAD]

Pin 3 is ground, 2 and 7 are the ignition signals from the ecu, 1 and 6 are the ignitor outputs to the -ve of the coils, pin 4 is the tach output and pin 6 is the 12v supply to the ignitor.

The tach out signal from the ignitor is a swiched ground and the components shown in the ecu in the pic are a diode, a 5v pullup resistor and a curent limiting resistor.

The diagram you posted with the diodes is only for if your tacho used to be triggered by the -ve of the ignition coil. Dont use it if your tacho got its signal from an ignitor or ecu.

[thegreatestben]

The original ignition was switched off've the negative side of the coil to my knowledge. I will confirm that now.

The coils and their function in my ignition system isn't an issue, that part was easy. I am just trying to establish how to get my stock tach working with wasted spark

[thegreatestben]

Apparently the original source for the tach was from the ignitor originally, not the coil -ve. So that means I need to do what?

[matt dunn]

Apparently the original source for the tach was from the ignitor originally, not the coil -ve. So that means I need to do what?

Try a 1K resistor between the VB and TAC terminals.

[thegreatestben]

Sweet, hopefully the smoke doesn't escape from any of my wires.
Thanks so far to all who have contributed, I also hope this provides other toyspeeders with the answers they need in the future