Fuel Delivery and Air Induction: Description and Operation

Engine Management Schematic:

Legend To Engine Management Schematic:

SYSTEM DESIGN
Bosch LH fuel injection is a multi-point, pulsed electronic fuel injection system. Used together with the EZL/AKR ignition system, it is designed to deliver a precise amount of fuel to each cylinder under various engine speed and load conditions.

Two separate fuel injection systems (one control unit per system) are required on the V12 engine. One system operates cylinders 1 through 6 and the other cylinders 7 through 12.

BASIC OPERATION
Fuel is delivered under pressure to the fuel rail (17) by two fuel pumps (M3m1 and M3m2). Fuel pressure in the fuel rail is held constant by a fuel pressure regulator (40). The fuel rail supplies fuel to twelve electric solenoid type fuel injectors (six Y63 and six Y64). Since fuel pressure is held constant, the amount of fuel that is injected is determined by the length of time the injectors are open (injection duration).

Fuel injection duration is controlled by the LH control units (N3/2 and N3/3). Each control unit determines injection duration by measuring various engine input signals and evaluating the signals in relation to pre-programmed values. Injection occurs once per engine revolution. Each injector is activated when the respective intake valves (two per cylinder) open. This is also known as sequential injection.

For additional information regarding the electronic control and programs of the fuel system, see Computer and Control Systems.

FUEL SYSTEM COMPONENTS
The components addressed for the fuel supply and air induction are:
^ Accelerator pedal
^ Air filter
^ EVAP system
^ Fuel cooler (74)
^ Fuel filter (55)
^ Fuel injectors (Y63 and Y64)
^ Fuel lines
^ Fuel pressure regulator (40)
^ Fuel pumps (M3m1 and M3m2)
^ Fuel pump relay (K27)
^ Fuel rail (17)
^ Fuel tank (75)
^ Intake air hoses
^ Throttle cable
^ Throttle valve