help with 89 jetta tachometer signal source?

[derekp]

I dont know if this is the right place to ask this....
We're slowly bringing up our 89 jetta 16v/aba turbo with ms 3.57
Sorting out the wiring - we're using a dual coil pack with 2 BIP drivers (wasted spark)

Can someone point me to something that might shed some light on a suitable signal source for the in-dash tach?
should I use one of the driver outputs to attache the tachometer lead to or must I derive its signal from something else?

thanks.

[trakkies]

Driving the OE tach from wasted spark is covered in the MegaManual.

[derekp]

searches for "tachometer" only lead me to this:
http://www.megamanual.com/ms2/EDIS.htm

Searches for "tach" provide lots of results, but all seem to be for INPUT triggering things for the MS to fire off of.

EDIS page shows tying my 2 coil triggers together with diodes.
I was wondering if there was some signal already available in the MS that would provide the needed output.
Apparently not, at least not from the searches I've done.
Anyone know of any other places in the manuals that might show more than the EDIS specifics?
thanks.

[trakkies]

If you want a 'low level' tach signal from MS you'll have to go to Extra Code, IIRC. As with so much else. How was the tach originally fed? If from a single coil, it may need a fairly large pulse to trigger it - something like 30-60 volts or so.