GDI -General Information13A-3 GENERAL INFORMATION The Gasoline Direct Injection System consists of sensors which detect the engine conditions, the engine-ECU or engine-A/T-ECU which controls the system based on signals from these sensors, and actuators which operate under the control of the engine-ECU or engine-A/T-ECU .The engine-ECU or engine-A/T-ECU carries out activities such as fuel injection control, idle speed control and ignition timing control. In addition, the engine-ECU or engine-A/T-ECU is equipped with several diagnosis modes which simplify troubleshooting when a problem develops. FUEL INJECTION CONTROL The injector drive times and injector timing are controlled so that the optimum air/fuel mixture is supplied to the engine to correspond to the continually-changing engine operation condi- tions. A single injector for each cylinder is mounted at the cylinder head. The fuel is sent under pressure from the fuel tank to the fuel pressure regulator (low pressure) by the fuel pump (low pressure). The pressure is regulated by the fuel pressure regulator (low pressure) and the fuel regulated is then sent to the fuel pump (high pressure). The fuel under increased pressure generated by the fuel pump (high pressure) is then regulated by the fuel pressure regulator (high pressure) and is then distributed to each of the injectors via the delivery pipes.Fuel injection is normally carried out once for each cylinder for every two rotations of the crankshaft. The firing order is 1-2-3-4-5-6. This is called sequential fuel injection. When the engine is cold or under a severe load, the “open-loop” control keeps the air/fuel ratio at a richer than usual level to maintain driveability. When the engine is under low or medium loads, the air/fuel ratio becomes leaner to reduce fuel consumption. When the engine is running at medium or high loads after having warmed up, the “closed-loop” control uses the signal from the oxygen sensor to keep the air/fuel ratio at the optimum theoretical level. THROTTLE VALVE OPENING ANGLE CONTROL This system controls throttle valve opening angle electronically. The engine-ECU or engine-A/T-ECU determines how deeply the accelerator pedal is depressed by means of the accelerator position sensor (APS). Then the engine-ECU or engine-A/T-ECU sends a target value of the throttle valve opening angle to the throttle valve controller. The throttle valve control servo operates the throttle valve so that it reaches the target opening angle. IDLE SPEED CONTROL This system maintains engine idle speed at a predetermined condition by controlling the air flow that passes through the throttle valve according to engine idling condition and engine loads at idling. The engine-ECU or engine-A/T-ECU operates the throttle valve control servoso that engine speed is maintained within a map value. The map value is predetermined according to engine coolant temperature and air-conditioning load. IGNITION TIMING CONTROL The power transistor located in the ignition primary circuit turns ON and OFF to control the primary current flow to the ignition coil. This controls the ignition timing in order to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timingis determined by the engine-ECU or engine-A/T-ECU from the engine speed, intake air volume, engine coolant temperature, atmospheric pressure and injection timing (intake stroke or compression stroke). www.WorkshopManuals.co.uk Purchased from www.WorkshopManuals.co.uk
