Fuel Delivery and Air Induction: Description and Operation
Fuel Injection System Diagram:
SYSTEM DESIGN
Bosch LH2.4 fuel injection is a multi-point, pulsed electronic fuel injection system. Used together with the EZ116K ignition system, it is designed to deliver a precise amount of fuel to each cylinder under various engine speed and load conditions.
BASIC OPERATION
Fuel is delivered under pressure to the fuel rail by two fuel pumps; an in-tank pump and a main pump. Fuel pressure in the fuel rail is held constant by a fuel pressure regulator. The fuel rail supplies fuel to four electric solenoid type fuel injectors. 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 fuel system ECU. The ECU 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 for all four injectors at the same time. (LH-2.4 is NOT a sequential injection system).
Features of the LH2.4 fuel system include:
^ Adaptive memory,
^ Self-diagnostics with fault code storage,
^ "Limp home" operating mode,
^ Separate cold-start injector, and
^ Anti-knock enrichment.
ADAPTIVE MEMORY
Time and mileage affect the operation of both the injection and the idle control systems. To compensate for wear and deposit accumulation, the LH2.4 system modifies its basic programming (within a "window" of operation) to provide efficient operation under all driving conditions. If the system determines that it must modify its basic programming beyond the "window", a fault code is stored in the self-diagnostic memory.
SELF-DIAGNOSTICS
The self-diagnostic system is a built-in function of the injection ECU. The ECU constantly monitors engine performance by comparing its programming "window" with the values it receives from various sensors. When a programming parameter has been exceeded, a retrievable fault code is stored.
LIMP HOME OPERATION
If the ECU determines that the air mass meter signal is incorrect, the system enters a pre-set "limp home" function. In "limp home" mode, a pre-set injection duration allows the vehicle to be driven to the nearest garage.
COLD START INJECTOR
During cold weather starting additional fuel is delivered to the intake manifold by an electrically operated cold start injector.
ANTI-KNOCK ENRICHMENT
If ignition knock cannot be counteracted by retarding ignition timing, the fuel system ECU provides a richer mixture to reduce combustion temperature.
FUEL SYSTEM COMPONENTS
The components addressed for the intake air and fuel delivery are:
^ Accelerator pedal
^ Air filter
^ Cold start injector
^ EVAP system
^ Fuel filter
^ Fuel injectors
^ Fuel pressure regulator
^ Fuel pumps
^ Fuel pump relay ([1][2]system relay)
^ Fuel rail
^ Fuel return line
^ Fuel supply line
^ Fuel tank
^ Intake air hoses
^ Suppressor relay
^ Throttle body
^ Throttle cable
Turbo System Schematic:
BASIC TURBO CHARGING SYSTEM OPERATION
The B230FT engine incorporates a turbo charger in the air induction system. The turbo charger compresses intake air to provide a higher cylinder fill rate. This higher fill rate results in an overall power increase. The normal fill rate of a cylinder in a naturally aspirated engine is about 85%. The turbo charged engine can fill the cylinder to a rate of approximately 95 - 120% (depending on boost pressure).
The turbo charger can be compared to an air pump which pumps air into the engine at higher than atmospheric pressure.
The turbo charger consists of a turbine wheel and a compressor wheel which are connected via a shaft.
The exhaust gases from the engine drive the turbine wheel and consequently the compressor wheel. When the exhaust pressure and velocity increase, so does the speed of the compressor wheel, which in turn pumps more air into the engine. A wastegate valve is incorporated to limit the maximum boost pressure in the intake manifold.
TURBO CHARGER COMPONENTS
The components for the turbo charging system are:
^ By-pass valve
^ Intercooler
^ Turbo charger
^ Wastegate valve
For additional information regarding FUEL SYSTEM components,