LE-Jetronic Fuel-Injection System
Automotive Engineering Research Assignment
1. Introduction
LE-Jetronic is an electronically controlled petrol-fuel-injection system developed from Bosch's L-Jetronic
family. It is a multi-point fuel-injection (MPFI) system in which fuel is delivered through individual
electrically operated injectors to the engine's intake ports.
Unlike a carburettor, which mechanically mixes fuel and air, LE-Jetronic uses an Electronic Control Unit
(ECU) and information from sensors to determine the amount of fuel required by the engine. The
principal measurement in the L-Jetronic family is the amount of air entering the engine, measured by an
airflow meter.
The system was designed to improve fuel metering, engine performance, fuel economy and emissions
compared with older carburettor systems.
2. Theory of LE-Jetronic
The basic theory is that the amount of fuel required by a petrol engine depends largely on the amount of
air entering the engine and the engine's operating conditions.
LE-Jetronic therefore uses an airflow sensor to measure incoming air. The sensor produces an electrical
signal that is sent to the ECU. The ECU combines this information with signals from other sensors and
determines how long the fuel injectors should remain open.
The injector opening time, often called injection duration or pulse width, determines the quantity of fuel
delivered.
3. Main Components
3.1 Electronic Control Unit (ECU): The ECU is the electronic control unit or 'brain' of the system. It
receives signals from the sensors, processes them and produces electrical control signals for the fuel
injectors.
3.2 Airflow Meter: The airflow meter measures the amount of air entering the engine. In the conventional
L/LE-Jetronic arrangement, a spring-loaded flap or vane is moved by incoming air. Its movement
changes the electrical output of a potentiometer, providing the ECU with information about airflow.
3.3 Fuel Pump: An electrically operated fuel pump draws fuel from the tank and supplies it to the
injection system under pressure.
3.4 Fuel Filter: The filter removes dirt and other contaminants from the fuel before it reaches the
injectors.
3.5 Fuel Rail: The fuel rail distributes pressurized fuel to the individual injectors.
3.6 Fuel-Pressure Regulator: The regulator maintains the required fuel pressure and returns excess
fuel to the fuel tank in systems designed with a return circuit.
3.7 Fuel Injectors: Electrically operated valves that spray finely atomized fuel into the individual engine
intake ports. The ECU controls their opening duration.
Automotive Engineering Research Assignment
1. Introduction
LE-Jetronic is an electronically controlled petrol-fuel-injection system developed from Bosch's L-Jetronic
family. It is a multi-point fuel-injection (MPFI) system in which fuel is delivered through individual
electrically operated injectors to the engine's intake ports.
Unlike a carburettor, which mechanically mixes fuel and air, LE-Jetronic uses an Electronic Control Unit
(ECU) and information from sensors to determine the amount of fuel required by the engine. The
principal measurement in the L-Jetronic family is the amount of air entering the engine, measured by an
airflow meter.
The system was designed to improve fuel metering, engine performance, fuel economy and emissions
compared with older carburettor systems.
2. Theory of LE-Jetronic
The basic theory is that the amount of fuel required by a petrol engine depends largely on the amount of
air entering the engine and the engine's operating conditions.
LE-Jetronic therefore uses an airflow sensor to measure incoming air. The sensor produces an electrical
signal that is sent to the ECU. The ECU combines this information with signals from other sensors and
determines how long the fuel injectors should remain open.
The injector opening time, often called injection duration or pulse width, determines the quantity of fuel
delivered.
3. Main Components
3.1 Electronic Control Unit (ECU): The ECU is the electronic control unit or 'brain' of the system. It
receives signals from the sensors, processes them and produces electrical control signals for the fuel
injectors.
3.2 Airflow Meter: The airflow meter measures the amount of air entering the engine. In the conventional
L/LE-Jetronic arrangement, a spring-loaded flap or vane is moved by incoming air. Its movement
changes the electrical output of a potentiometer, providing the ECU with information about airflow.
3.3 Fuel Pump: An electrically operated fuel pump draws fuel from the tank and supplies it to the
injection system under pressure.
3.4 Fuel Filter: The filter removes dirt and other contaminants from the fuel before it reaches the
injectors.
3.5 Fuel Rail: The fuel rail distributes pressurized fuel to the individual injectors.
3.6 Fuel-Pressure Regulator: The regulator maintains the required fuel pressure and returns excess
fuel to the fuel tank in systems designed with a return circuit.
3.7 Fuel Injectors: Electrically operated valves that spray finely atomized fuel into the individual engine
intake ports. The ECU controls their opening duration.
