When the signal for manual override is held below 1 volt, the Magneto Interface Box (MIB) is in the electronic timing mode. The Timing Control Module (TCM) generates the magneto interface clock signal by changing the signal from the speed sensor to a square wave.
The magneto interface clock signal provides information for the MIB in order to determine the crankshaft position.
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| Illustration 1 | g00697160 |
Nine edges of the signal from the magneto interface clock Note that there are two edges for each cycle. | |
When the magneto reset pulse signal is received from the TCM, the MIB counts nine edges from the magneto interface clock signal. Then, the MIB sends a signal to the magneto in order to fire the number one cylinder.
The MIB continues to monitor the magneto interface clock signal. The MIB signals the magneto to fire the remaining cylinders throughout the rotation at the respective counts of the clock for the cylinders. When the magneto's odd ordered capacitor discharges in order to fire the cylinder, an ignition pulse is generated. The ignition pulse signal is a reduced voltage signal of the odd ordered capacitor voltage.
Ignition timing is calculated by comparing the timing offset between the Crank Angle Sensor Pulse and the Ignition Pulse for the number one cylinder.
When the Manual Override Signal exceeds 1 volt, the MIB operates in Manual Mode. The MIB no longer signals the magneto to fire. The magneto discharges the capacitors when the internal, mechanical trigger is activated. The Ignition Pulse Signal is generated from the odd ordered capacitor discharge. The ignition timing is calculated in the same manner as the Electronic Timing Mode.