Computers and Control Systems: Description and Operation

Fuel Injection System Schematic:

The Computerized Engine Controls (CEC) electronically regulate the air/fuel ratio, idle speed and ignition timing. This is done by two Electronic Control Units (ECU), one controlling the fuel injection system and the other controlling the ignition system.

FUEL INJECTION SYSTEM (BOSCH LH2.2-JETRONIC):

BOSCH LH2.2-JETRONIC stands for:

BOSCH = manufacturer
L = luft (German for air)
H = heiss (German for hot as in hot-wire)
2.2 = model series

This fuel injection is based on the Bosch multi-point fuel injection system with hot-wire air mass meter (LH-Jetronic). The ECU uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information it will adjust the injector frequency to provide optimal air/fuel mixture, performance, driveability and emissions output.

Input devices (the ECU receives):

^ Ignition switch signal.
^ Oxygen sensor (lambda sond) signal.
^ Engine speed (RPM) signal from the ignition control unit
^ Knock signal from the ignition control unit
^ Coolant temperature signal.
^ Air mass meter signal.
^ Throttle position signal.
^ A/C control signal from climate control panel.
^ Turbo over-boost pressure signal.

Output devices (The ECU controls):

^ [1][2]System relay ground.
^ Suppressor relay via the [1][2]system relay.
^ Ballast resistor
^ Fuel injector ground.
^ Idle air valve.
^ Air mass meter signal to the ignition system control unit (ignition ECU input device).
^ Shift indicator light.

Ignition System And Components:

IGNITION SYSTEM (BOSCH EZ117K):

BOSCH EZ117K stands for:

BOSCH = manufacturer
E = elektronische (German for electronic)
Z = zuendung (German for ignition)
117 = model series
K = klopfregelung (German for knock control)

This ignition is based on the fully electronically controlled Bosch hall-effect ignition system with knock control (EZ-K). The ECU uses electrical input signals from various devices and sensors to calculate the engine load and condition. With this information the ECU will adjust the ignition timing to provide optimal performance, driveability and emissions output.

Input devices (the ECU receives):

^ Ignition switch signal.
^ Crankshaft position and speed (hall-effect) signal.
^ Knock signal.
^ Air mass meter signal from fuel injection control unit.
^ Throttle position signal.
^ A/C control signal from climate control panel.
^ A/C pressure sensor signal.

Output devices (The ECU controls):

^ Power stage.
^ Engine speed (RPM) signal to the fuel injection control unit (fuel injection ECU input device).
^ Knock signal to the fuel injection control unit (fuel injection ECU input device).
^ Crankshaft position and speed (hall-effect) sensor power supply (12V).