well, I spent yesterday on the 'teen and one of my 'do do's for the day was
to figure out why my tach is not working.

I just bought the car and have had it for about 1.5 weeks. the previous
owner said something about a "high output ignition" when I bought it but
seeing the pertronix leads and a normal black coil I thought it was odd for
him to call it high output.

anyway, I had noticed an annoying high-pitched noise when turning on the
car and since it is no longer fuel injected I wondered what it could be.

So hunting around the engine compartment I followed some odd wires back
under the battery tray where I found a big box with fins. Take a
small mirror I was abe to see it was a bosch CDI unit.

I disconnected it and ran the ignition normally and now my tach works
and the car runs fine.

So what will the CDI do for me? It is a stock 1.7 with 40 dells. Is there
really a point to run it? to be honest, I think a tach would be more benificial
to my engine than a bigger spark.

Should I run it? is there something Im missing?

The theory of the CDI system is a hotter spark (more volts) to run a larger gap on the plugs (better fuel/air mixture ignition) and less saturation time required for a big spark (capacitor saturates much faster than copper windings).

First it is not run with a "normal" coil ..... it is run with a transformer (which looks like a coil). "Normal coils" are fed about 9 VDC ... 12 VDC is stepped down via an external or internal resistor to the primary windings. The "Normal" Bosch Blue coil has an internal resistor.

The "Transformer" of the Bosch CDI system is fed 400 VDC by the CDI unit.

Keep it? Hell yes. Expensive to replace? Hell yes.

Oh, the whine is the capacitor charging .... it's a cool sound 'cause if you don't hear it you're either deaf to that frequency range (like me) or it's $200+ dollars 'cause it's no good.

Your tach should have worked with it ...........

thanks for that info. I had no idea.

I would keep it if my tach worked with it.
I did some research and it seems like it was hooked up incorrectly.
from what Ive seen, the 3 wires are:
•ground wire
•positive wire(to + side of "transformer" coil thingy)
•and tach lead.

does this sound correct?