Integrated Electronic Ignition System (High Data Rate)

Ignition Systems

Overview

The Ignition System is designed to ignite the compressed air/fuel mixture supplied to the engine by the fuel and air systems. The ignition system also provides engine timing information to the Powertrain Control Module (PCM) for proper vehicle operation.

Integrated Electronic Ignition System (High Data Rate)

The Integrated Electronic Ignition (EI) system consists of a PCM a Crankshaft Position Sensor (CKP) and connecting wiring harnesses. The PCM contains the ignition control hardware for Profile Ignition Pickup (PIP) Spark Output (SPOUT) Ignition Ground (IGN GND) and Ignition Diagnostic Monitor (IDM). Six cylinder applications use a six tower coil pack. Eight cylinder and dual plug applications use two four tower coil packs. Four cylinder applications use a single four tower coil pack.

The EI High Data Rate system eliminates the need for a distributor by using multiple coil packs. Each coil within the pack fires two spark plugs at the same time. The plugs are paired so that as one fires during the compression stroke the other fires during the exhaust stroke. The next time the coil is fired~ the plug that was on exhaust will be on compression and the plug that was on compression will be on exhaust.

The coil on plug works in the same manner as a standard coil pack. The coil on plug systems fire only one spark plug at a time instead of two like the standard coil packs. Since there is one coil on each spark plug the coils will fire the spark plugs on the compression stroke only. Coils no longer fire spark plugs on the exhaust stroke. The PCM uses information from the CMP to identify the position of cylinder one in order to synchronize the firing of the coils.

The CKP is used to indicate crankshaft position and speed information to the PCM. By sensing a missing tooth on a trigger wheel mounted on the crankshaft damper the CKP is also able to identify a specific point in the travel of piston 1. The PCM uses the information from the CKP to generate an internal Profile Ignition Pickup (PIP) signal.

Once the PIP signal is generated fuel and spark functions are enabled. The calculated spark target is used internally by the PCM as a pulse width modulated digital signal called the Spark Output (SPOUT). The PCM decodes the SPOUT signal and fires the next spark at the commanded spark target. The PIP signal is also used to supply a clean inverted signal (PIP) for tachometer operation.

The PCM also serves as an electric switch for a coil primary circuit. When the switch closes current flows and a magnetic field expands around the primary coil. When the switch opens the field collapses and causes the secondary coil to fire the spark plugs at high voltage. In addition an Ignition Diagnostic Monitor (IDM) signal is transmitted on each spark firing. This signal communicates information by pulse width modulation.






Hardware

Crankshaft Position Sensor

The Crankshaft Position (CKP) sensor is a magnetic transducer mounted on the engine block adjacent to a 36 minus one tooth trigger wheel located on the crankshaft. By monitoring the crankshaft mounted trigger wheel the CKP is the primary sensor for ignition information to the PCM. By monitoring the trigger wheel the CKP indicates crankshaft position and speed information to the PCM. By monitoring the missing tooth the CKP is also able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to a fixed reference. Refer to Figures 7, 14.









Camshaft Position Sensor

The Camshaft Position Sensor is a magnetic transducer mounted on the front cover adjacent to the camshaft. By monitoring a target on the camshaft sprocket the CMP identifies cylinder one to the PCM. The I-EI system uses this information to synchronize the firing of the Coil per Plug.

Powertrain Control Module

The Powertrain Control Module (PCM) (Figure 17) receives IGN GND and PIP signals from the ICM and generates a SPOUT signal based upon engine speed load temperature and other sensor information.






Coil Pack

The coil is turned on (i.e. coil charging) by the PCM then turned off firing two spark plugs at once. The spark plugs are paired so that as one spark plug fires on the compression stroke the other spark plug fires on the exhaust stroke. The next time the coil is fired the situation is reversed. The next pair of spark plugs fire according to the engine firing order etc. Refer to Figure 20.