Hello All.
Where does a tacho get its signal from when using a modern engine such as a zetec.?

depends on what ignition usually the - side of a coil.

Diesel cars tend to use the alternator

In a zetec it would be the (green?) wire from the ECU or EDIS.

Wherever the manufactures get their Taco signal from, should be easy to find in the Heynes, provided your Taco accepts this kind of input.

Thanks chaps.
It's a wasted spark system so the coil idea doesn't work.

I was thinking the ECU so the Ecu or EDIS makes ense.

My Haynes manual says white/black wire from terminal 11 on the ignition module.

Without knowing which ECU it's hard to say where to pick up Tacho signal.
I'm having similar thoughts at the moment as I need to pick up a tacho drive sigmal from my MegaSquirt.
What occurs to me is that the standard signal from MS that goes to the EDIS comes directly out of the processor chip with no interface and I believe it has a max current rating of about 10MA.
This is fine for EDIS but if you drive your tacho from this as well you may overload the output, depending of course what sort of current your tacho sinks.
The answer I guess would be to install the "high current driver" transistor in MegaSquirt. This will still drive the EDIS ok but will allow you to sink more current through the cars tachometer.