Igniter Operation

When the IGt signal goes high, the primary circuit power transistor TR2 turns on, allowing cur-rent to flow in the coil primary winding. When the IGt signal goes low, the igniter interrupts primary circuit current flow, causing voltage induction into the coil secondary winding.

With the ESA system, the time at which the power transistor in the igniter turns on is further influenced by a dwell control circuit inside the igniter. As engine rpm increases, coil dwell time is increased by turning the transistor on sooner. Therefore, the time at which the transistor is turned on determines dwell while the time the transistor is turned off determines timing. Timing is controlled by the ECU; dwell is controlled by the igniter.

Controlling dwell within the igniter allows the same control over coil saturation time as the ballast resistance does with the Conventional EFI ignition system. It allows maximum coil saturation at high engine speeds while limiting coil and igniter current, reducing heat, at lower speeds.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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