Engine management system - EDC (Description): Description and operation

Description

General

The Td4 engine has an Electronic Diesel Control (EDC) engine management system. The system is controlled by an Engine Control Module (ECM) and is able to monitor, adapt and precisely control the fuel injection. The ECM uses multiple sensor inputs and precision control of actuators to achieve optimum performance during all driving conditions.

The advantages of the system are: l Greater fuel economy. l Reduced exhaust emissions. l Reduced engine noise. l More effective cold starting. l Smoother engine operation.

The ECM controls fuel delivery to all four cylinders via a Common Rail (CR) injection system. The CR system uses a fuel rail to accumulate highly pressurised fuel and feed four electronically controlled fuel injectors. The fuel rail is located in close proximity to the four fuel injectors, which maintains full system pressure at each injector at all times.

The ECM utilises the drive by wire principle for acceleration control. There are no control cables or physical connections between the accelerator pedal and the engine. Accelerator pedal demand is communicated to the ECM by the throttle potentiometer, which is installed on the pedal box. A variable reading from the throttle potentiometer, enables the ECM to determine the position, and the rate and direction of movement of the accelerator pedal. The ECM uses this information to facilitate the correct engine response.

The ECM controls the Exhaust Gas Recirculation (EGR) system which is fitted to reduce the formation of oxides of nitrogen (NO_x). This group of gases is formed in the combustion chamber under conditions of high temperature and pressure. It is not desirable to reduce the compression ratio, so the ECM reduces the combustion temperature by introducing a controlled volume of inert gas into the cylinders on the induction stroke.

The inert gas used is exhaust gas, which is freely available. It is directed from the exhaust manifold, via a control valve, into the intake manifold. The flow of gas is monitored by the ECM using the MAF sensor. The EGR system is not required until the engine is hot, and is turned off during engine idling and wide open 'throttle' to preserve smooth operation and driveability.

The ECM processes information from the following input sources: l Brake switch. l Clutch switch (manual gearbox models). l Crankshaft Position (CKP) sensor. l Camshaft Position (CMP) sensor. l Anti-lock Brake System (ABS) ECU. BRAKES, DESCRIPTION AND OPERATION, Description. l Engine Coolant Temperature (ECT) sensor. l Boost Pressure (BP) sensor. l Low side fuel pressure sensor. l Throttle potentiometer. l Mass Air Flow/ Intake Air Temperature (MAF/ IAT) sensor. l Fuel rail pressure sensor. l Controller Area Network (CAN). COMMUNICATION DATA BUSES, DESCRIPTION AND OPERATION, Description.