Hi John,
Most distributor setups need at least 3 wires...
- Trigger wire: the distributor usually has some sort of trigger device in it and this is the signal out to your box. You don't HAVE to use this if you have some other means of triggering the ignition (crank trigger pickup, etc.). This device is usually a reluctor/pickup, LED....
- +12V: The trigger device inside generally needs 12V input to create the output trigger signal.
- Ground: Even though the distributor probably is grounded internally, everything always has a real ground wire as part of the harness.
The multi-spark thing is a farce for a race car. The MSD boxes only have multiple sparks below 3500 RPM. Usually, they make three sparks per firing below 3000, then they drop back to only two until 3500. By 3600 RPM, they are ONE spark per firing.
For a street car running down the road, this is great. But it doesn't do anything for a race car at all.
The most UNDESIRABLE spark characteristic is that as RPM increases, it'll need another AMP per 1000 RPM. As supply voltage and current to the box drops (unless you're running a charging system), your spark will diminish. More spark cycles means it needs more energy and after starting your car, the batteries take a dip and spark suffers.
