Tacho wiring for 20V

[Bentley]

I have a japanese GTV Trueno from 1983 with a Silvertop 20V engine that the previous owner swapped.

My problem is that my tachometer is not working.

I have been looking around on the internet for a while with little success.

So, does anyone here know what wires I need to connect? From where to where?

[jondee86]

You need to find this plug....



It is located high on the firewall behind the engine, and connects the
dash loom to the engine loom. Depending on the version (USDM, JDM,
EUR etc) the plug may have less wires than shown, but the main ones
will be there.

Then take a wire (splice it to the existing) from the coil negative and
connect it to the tacho wire.

Job done

Cheers... jondee86

[fax0815]

That works if your car runs standard ECU, if it runs a standalone ecu you need a little converter that turns the positive square tacho singnal output into a negative peak signal, which will then work with your tacho in the car.

You can run can also use the one black fro the ignitor, thats a designated tacho signal as well and will provide the correct signal to connect to the wire above.

[Bentley]

I have the Haltec e6x ECU, so what does that tell me?

[jondee86]

Quote:Then take a wire (splice it to the existing) from the coil negative and
connect it to the tacho wire.

Tacho needs the flyback voltage spike generated by the coil. The wire in
the pic would normally be connected to the OEM igniter, and would get the
signal from there. Since I don't know what ignition system you are using,
I just assumed you would be using the ST coil, which has a plug instead
of open terminals. Therefore I suggested splicing to the negative wire, as
that is where the spike originates.

If you have multiple coils, MSD or some other fancy ignition, it can get
a bit more complicated. Signal converters or pull-up coils are only
required if you are trying to use a low-level tacho signal from the ECU.

Cheers... jondee86

[fax0815]

Are you running standard Toyota ignitor?
Then you just use black wire with the red dots and connect it to the tacho wire in the picture above.

If you don´t:
Your halltech ECU should have a "tacho" output, find that!
Not familiar with halltech, but you might have to configure an AUX out for this?

Buy a signal converter, I normally use Omex, which is about 20-25Euro wire it in as shown in the manual.
And the rev counter works again, done this with 2 20V already, it is quiet funny to look at, as it pulls way past the redline...