The ignition systems used on today's EFI/TCCS equipped engines are not that much different from the ignition system used on the original 4M-E EFI engine. Primary circuit current flow is controlled by an igniter based on signals generated by a magnetic pickup (pickup coil) located in the distributor.
The ignition system has a dual purpose, to distribute a high voltage spark to the correct cylinder and to deliver it at the correct time. Ideal ignition timing will result in maximum combustion pressure at about 10' ATDC.
The most significant difference between TCCS and Conventional EFI ignition systems is the way spark advance angle is managed. The Conventional EFI system uses mechanical advance weights and vacuum diaphragms to accomplish this. Starting with the 5M-GE engine in 1983, the TCCS system controls ignition spark timing electronically and adds an ignition confirmation signal as a fail-safe measure.
There are two versions of electronic spark management used on TCCS equipped engines, the Electronic Spark Advance (ESA) and the Variable Advance Spark Timing (VAST) systems.
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