Next you need to make a decision. There are two input circuits for the tach signal. One takes the square wave input from a hall sensor, optical sensor, or points. The other circuit takes the AC signal from a variable reluctor sensor and converts it to a square wave for use by MegaSquirt. In most cases, you should install both circuits, and make the selection between them with jumpers. However, if you do not want to install the Hall/optical/points circuit, skip ahead to step #51.


So on an M50, '91 non vanos, what should I do?