In the Conventional EFI system, spark advance angle is determined by the position of the distributor (initial timing), position of the magnetic pickup reluctor teeth (centrifugal advance), and position of the breaker plate and pickup coil winding (vacuum advance). The spark advance curve is determined by the calibration of the centrifugal and vacuum advance springs.
Besides being subject to mechanical wear and mis-calibration, this type of spark advance calibration is very limited and inflexible when variations in coolant temperature and engine detonation characteristics are considered. Mechanical control of a spark curve is, at best, a compromise. In some cases the timing is optimal; in most cases it is not.
Was this article helpful?