Operation

FUEL SYSTEM:
Fuel is pumped up by the fuel pump, which flows through the fuel filter under pressure through the fuel pipe to the delivery pipe where it is distributed to each injector.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel line (high pressure side) to a pressure 284 kPa (2.9 kgf/cm2, 41 psi) higher than the pressure inside the intake manifold, and excess fuel is returned to the fuel tank through the return tube.
In the California specification models, when the engine is extremely hot, the ECM turns on the Vacuum Switching Valve (VSV) and the fuel pressure is increased to control percolation in the fuel system and improve restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure caused by the injector.
Fuel is injected into the intake manifold according to signals from the ECM.





AIR INDUCTION SYSTEM:
Air filtered through the air cleaner passes through the Volume Air Flow (VAF) meter and the amount flowing to the air intake chamber is determined by the throttle valve opening in the throttle body and the engine speed. VAF meter measures the intake flow to the engine by the swirl frequency.
Located in the throttle body is the throttle valve, which regulates the volume of air intake to the engine. Air intake controlled by the throttle valve opening is distributed from the intake chamber to the manifold of each cylinder and is drawn into the combustion chamber.
At low air temperature the IAC valve opens and the air flows through the IAC valve, as well as the throttle body, into the air intake chamber. During engine warm up, fast idle is accomplished by air flowing into the intake chamber via the IAC valve, even when the throttle valve is completely closed.
The air intake chamber prevents pulsation of the intake air. reduces the influence on the VAF meter and increases the air intake volume. It also prevents intake air interference in each cylinder. There is also the intake air control valve attached to the air intake chamber. Part of the ACIS, the ECM provides signals to the VSV to open or close. This valve opens or closes the vacuum source to the actuator, which in turn opens or closes the intake air control valve. The intake air control valve is designed to modify the effective manifold length in 2 stages for increased power in all driving ranges.





ELECTRONIC CONTROL SYSTEM:
The control system consists of sensors which detect various engine conditions, and an ECM which determines the injection volume and injection timing based on the signals from the sensors.
The various sensors detect the air intake volume, engine speed, oxygen density in the exhaust gas, engine coolant temperature, air intake temperature and atmospheric pressure etc. and convert the information into an electrical signal which is sent to the ECM. Based on these signals, the ECM calculates the optimum fuel volume and injection timing for the current conditions and operates the injectors.
The ECM not only controls the fuel injection timing, but also the self diagnostic function which records the occurrence of a malfunction, ignition timing control, idle speed control, intake air control for ACIS, fuel pressure control, EVAP control, EGR control and fuel pump control, which switches between the high and low fuel pump speeds according to varied load conditions.