Electronic Spark Timing With Electronic Spark Control (EST/ESC)

This is a closed loop system that controls engine detonation by adjusting spark timing. This system consists of EST system, detonation sensor, modified electronic control module in HEI distributor and a controller.

The detonation sensor is mounted in engine block (behind intake manifold) and it detects presence (or absence) and intensity of detonation by vibration characteristics of engine. Sensor sends electrical signal to controller. If sensor fails, no retard will occur. The controller constantly processes sensor signal into command signal to distributor to adjust spark timing. Controller failure would cause either no ignition, no retard or full retard.

The distributor receives commands from controller, and spark firing is delayed while detonation is occurring, thus providing required retard. The amount of retard is a function of degree of detonation. The EST/ESC system is used on 3.8L (VIN Code 3), 4.1L and 4.9L (VIN CODES W and T) engines.