Fuel Delivery and Air Induction: Description and Operation

PURPOSE

Fuel Delivery System:

Fuel Delivery
The Sequential Fuel Injection (SFI) delivers correct air/fuel mixture to the engine at the precise time throughout its entire RPM range and under all operating conditions.

Air Induction
The air induction system filters, controls, silences and delivers fresh air to the engine.

OPERATION

Fuel Delivery System Schematic:

Fuel Delivery
A high-pressure in-tank mounted fuel pump delivers fuel to the fuel injection supply manifold. The fuel injection supply manifold incorporates electrically actuated fuel injectors mounted directly above each of the engine's intake ports.

Fuel pressure across the injectors is maintained by a pressure regulator. Because fuel pressure is a constant while fuel demand is not, the system includes a fuel return line that allows excess fuel to flow through the regulator to the fuel tank.

The amount of fuel the injectors will spray under a particular operating condition is determined by a Powertrain Control Module (PCM). This assembly receives electrical signals from sensors that monitor factors such as airflow pressure and temperature to the engine, engine coolant temperature, throttle position, vehicle speed, etc.. The PCM evaluates the sensor information and signals the fuel injectors, controlling injector pulse width.

Air Induction
Air enters the system through the fresh air duct and flows through the air cleaner and is monitored by the Mass Air Flow (MAF) sensor. The metered air passes through the air duct and enters the throttle body. From the throttle body, the air passes through the intake plenum to the intake manifold, where it is mixed with fuel for combustion.

Fuel Injection Timing
The fuel injectors are energized in the following sequence: 1, 4, 2, 5, 3, 6.

The period of time that the fuel injectors are energized (fuel injector on time or pulse width) is controlled by the vehicle's Powertrain Control Module (PCM). Air entering the engine is measured by a Mass Air Flow (MAF) sensor. This air flow information and input from various other electronic engine control sensors is used to compute the required fuel flow rate necessary to maintain a prescribed air/fuel ratio for engine operation.

The PCM determines the needed fuel injector pulse width and outputs a command to the fuel injectors to meter the exact quantity of fuel.