The distributor ignition system differs from the conventional breaker points system in form only; its function is exactly the same: to supply a spark to the spark plugs at precisely the right moment to ignite the compressed air/fuel mixture in the cylinders and create mechanical movement.
Located in the distributor, in addition to the rotor, is a spoked reluctor which is pressed onto the distributor shaft. The reluctor revolves with the rotor; as it passes a pickup coil inside the distributor body, it breaks a high flux field, which occurs in the space between the reluctor and the pickup coil. The breaking of the field allows current to flow to the pickup coil. Primary ignition current is then cut off by the Powertrain Control Module (PCM), allowing the magnetic field in the ignition coil to collapse, creating the spark which the distributor passes on to the spark plugs.
The distributor ignition system has timing controlled by the Powertrain Control Module (PCM). The standard reference ignition timing data for the engine operating conditions are programmed in the memory of the PCM. The engine conditions (rpm, load and temperature) are detected by various sensors. Based on these sensor signals and the ignition timing data, a signal is sent to interrupt the primary current at the power transistor. The ignition coil is activated and a spark sent through the distributor, down the spark plug wires to the spark plugs. Ignition timing is controlled by the PCM for optimum performance.
The distributor ignition system can be identified by looking for the presence of a distributor (with spark plug wires connecting the distributor cap to the spark plugs). If no distributor is found, it can be assumed that the engine uses a distributorless ignition system. Coverage of the distributorless ignition system is found later in this section.
Acura ignition systems are basically comprised of a distributor, an ignition control module, a control box, a high energy coil and related ignition wires. The distributor contains a reluctor mounted on a rotor shaft and a magnet mounted on a base plate. The pick-up coil is located around the rotor shaft but does not rotate with the shaft. The programmed ignition employed on these vehicles, provides optimum control of ignition timing by determining the optimum timing using a microcomputer in response to engine speed and vacuum pressure in the intake manifold, which are transmitted by signals from CRANK/CYL sensor, TDC sensor, throttle angle sensor, coolant temperature sensor and MAP sensor. This system, not dependent on a governor or vacuum diaphragm, is capable of setting lead angles with complicated characteristics which cannot be provided by conventional governors or diaphragms.
The ignition control module contains 3 resistors, 3 diodes and 2 transistors. The transistors act as switches which are activated at a precise voltage. When the ignition is switched ON , the switching of the transistors in the ignition control module ensures that no current can flow in the ignition coil primary windings. When the engine is cranked, the reluctor moves through the magnetic field created by the stator and, when the reluctor teeth are aligned with the stator projections, a small AC voltage is created. The ignition control module amplifies this voltage and uses it to switch the transistors so that an earth path is provided to the primary circuit.
As the reluctor teeth move out of alignment with the stator projections, an abrupt change occurs in the AC voltage. The transistors are switched again and the primary circuit earth path is broken. This induces a high voltage in the ignition coil secondary winding.
A time control circuit in the ignition control module controls the charging time for the ignition coil according to engine speed, this reduces consumption at low engine speeds and prevents secondary voltage drop at high engine speeds.