DESCRIPTION
Ignition timing is controlled by the ECCS control unit. Optimum timing for all engine conditions has been programmed into the ECCS control unit.
Signals used for determination of ignition timing come from the cylinder head temperature sensor, airflow sensor, throttle valve switch, vehicle speed sensor, detonation sensor, crank angle sensor, signal rotor plate and ignition coil. Signal from the ECCS control unit is sent to the power transistor of the ignition coil to control the ignition timing.
CYLINDER HEAD TEMPERATURE SENSOR
On 200SX Turbo coolant temperature sensor is located in the coolant outlet. On Maxima, 300ZX models, and 1986 1/2 Pickup, the cylinder head temperature sensor is located in the cylinder head near the thermostat housing. The sensor monitors changes in cylinder head temperature and transmits a signal to the ECCS control unit.
AIRFLOW METER
The airflow meter measures the mass flow rate of the incoming air. The control unit emits an electrical output signal in relation to the amount of heat dissipated from the hot wire placed in the stream of intake air.
THROTTLE VALVE SWITCH
The throttle valve switch is attached to the throttle chamber and actuates in response to accelerator pedal movement. The throttle valve switch is open when the throttle is being moved, and closed when the engine is idling. The switch also contains a set of full throttle contacts. These are used on electronically controlled automatic transmission on Maxima, 300ZX and 300ZX Turbo models.
VEHICLE SPEED SENSOR
The vehicle speed sensor provides a vehicle speed signal to the ECCS control unit. The speed sensor consists of a reed switch, which is installed in the speed meter unit and transforms vehicle speed into a pulse signal. On digital type speedometer models, the sensor consists of an LED, photo diode, shutter and wave forming circuit. Its principle is the same as that of the crank angle sensor.
DETONATION SENSOR
The detonation sensor is located on passenger's side of engine block. It sends a signal when "knocking" occurs. The control unit modifies ignition timing to reduce detonation.
CRANKSHAFT ANGLE SENSOR
The crank angle sensor is a basic signal sensor for the entire ECCS. It monitors engine speed and piston position, and it sends signals to the ECCS control unit for control of ignition timing.
The unit is built into the distributor, and has 2 diodes and a wave-forming circuit. When a signal rotor plate passes the space between light emitting diode (LED) and photo diode, the slit to the signal rotor plate alternately cuts the light which is sent to the photo diode from the LED. This causes a pulsating voltage which is converted into an on-off pulse by the wave-forming circuit and sent to the control unit.
Ignition Timing Control Diagram. Scheme 16
SIGNAL ROTOR PLATE
The signal rotor plate has 360 slits at 1° intervals on outside edge. It also has 4 or 6 slits (depending on engine size) at 90° and 120° intervals. These slits are used to detect crank angle (piston position). The teeth are used to provide the 1° signal that is necessary to control engine RPM and ignition timing.
IGNITION COIL
The ignition coil has a built-in power transistor. The signal from the control unit is amplified by the power transistor. This signal is used to connect and disconnect the ignition coil's primary current to generate high voltage across the secondary coil, thus creating a spark across the spark plug.
COMPONENT TESTING
Note. For testing and inspection of these components, refer to appropriate article in the COMPUTER CONTROLS section.