Electronic Ignition EI (High Data Rate)

Ignition System

Overview

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

Electronic Ignition System (EI High Data Rate)

The EI High Data Rate systems consist of an Ignition Control Module (ICM), a Crankshaft Position Sensor (CKP), a PCM and connecting wiring harnesses. Six cylinder applications use a six tower coil pack and eight cylinder applications use two four tower coil packs.

The vehicles that use an EI system with a stand-alone ICM are the Mustang, Thunderbird, Cougar, Crown Victoria, Grand Marquis, Town Car and Windstar.

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 CKP is used to indicate crankshaft position and speed information to the ICM. 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 ICM uses this information from the CKP to generate a Profile Ignition Pickup (PIP) signal that is sent to the PCM.

Once the PCM recognizes the PIP signal, fuel and spark functions are enabled. The calculated spark target is sent from the PCM to the ICM as a pulse width modulated digital signal called the Spark Output (SPOUT). The ICM decodes the SPOUT signal and fires the new spark at the commanded spark target.

Coil firing is initiated by energizing the ICM coils in sequence using the missing tooth as a reference and firing at the commanded spark target.

By energizing the primary side of the coils on proper sequence and connecting the secondary wires in accordance with the engine firing order, a power stroke is achieved on each cylinder. In addition, an Ignition Diagnostic Monitor (IDM) signal is transmitted on each spark firing. This signal communicates information by pulse width modulation and provides a clean, buffered signal with a frequency proportional to engine speed for tachometer operation.

The ICM 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.

For EEC-V Integrated-EI Components and System Description, refer to the EEC-V Hardware and Software.









Hardware

Crankshaft Position Sensor

The Crankshaft Position Sensor (CKP) 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 ICM. The trigger wheel has a total of 35 teeth spaced 10 degrees apart with one empty space for a missing tooth. By monitoring the trigger wheel, the CKP indicates crankshaft position and speed information to the ICM. 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 ofthe crankshaft relative to a fixed reference. Refer to Figures 1,2 and 3.






Ignition Control Module

The primary function of the Ignition Control Module (ICM) is to deliver full energy spark at a crank angle targeted by the PCM and provide the PCM with crankshaft position information. The 1CM also produces an Ignition Diagnostic Monitor (IDM) signal that is sent to the PCM. Refer to Figure 4.






Powertrain Control Module

The Powertrain Control Module (PCM) (Figure 5) receives IGN GND and PIP signals from the ICM, and generates a SPOUT signal based upon engine speed, load, temperature and other sensor information. An IDM signal is received from the ICM to determine if an ignition failure mode should be recorded.






Coil Pack

The coil is turned on (i.e. coil charging) by the ICM, 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 Figures 6 and 7.