printable version

Fuel system

Elements of control and motor control

Management of the fuel system performed ECU ECM (Engine Control Module). ECM conducts adjustment of the ignition timing, determines the amount of fuel supplied to the engine, the system controls the emission control and speed of the crankshaft of the engine idling and the air conditioning compressor clutch, etc. The ECM changes the modes of operation of the engine according to the varying operating conditions on the basis of signals from various switches and sensors.

For example, the ECM adjusts the ignition timing based on the sensor signals, which are responsive to the engine speed, coolant temperature, throttle position, is currently included in the transmission, vehicle speed, etc.

The ECM controls the engine speed of idling based on the sensor signals, which are responsive to throttle position, vehicle speed included in the active time of the transfer, etc.

Sensor meter air flow (MAF - Mass Airflow Sensor)

Meter of air provides the most direct method to measure the load of the engine, as it measures the amount of air entering the engine. Feed air enters the engine through the meter with a hot and cold wire elements forming part of a bridge circuit. The current passing through the heated wire member maintains constant its temperature at a constant level, which is higher than the temperature of air entering the engine. Air mass is determined by the current strength required to maintain the temperature of the wire member. The greater the air flow, and naturally cooling thereof, the greater the value of the signal applied to the ECM.

Coolant temperature

The coolant temperature sensor monitors the temperature of the coolant and on the basis of the sensor signal, the ECM calculates the width of the pulse supplied to the nozzle, thereby changing the amount of fuel supplied to the engine cylinders, and the ignition timing changes.

On cold engine ECM operates in open loop mode, whereby in the cylinder chamber is fed a richer air-fuel mixture and increases the idle speed. This continues until the motor has reached its normal operating temperature.

Throttle position (TP - Throttle Position)

Throttle position sensor transmits the information upon which the ECM determines when the throttle is closed, fully open or is the intermediate positions. The sensor is rigidly connected to the throttle shaft. Depending on the throttle position sensor resistance changes. To power the transmitter with ECM for the unit 5 V output voltage of the sensor is changed from 0.25 V at minimum throttle to 4.7 V at full throttle.

Sensor crank angle (CKP - Crankshaft Position Sensor)

Sensor crank angle passes the ECM information about the position of the crankshaft. Based on the information of the output signal of the sensor and the signal of the camshaft sensor, the ECM detects the ignition timing and the cylinder, which must be supplied with fuel. In the absence of the sensor output signals the engine starts.

Camshaft position sensor (CMP - Camshaft Position Sensor)

Camshaft position sensor generates pulses based on which the ECM identifies the first cylinder and the opening of the nozzle.

Knock sensor

Knock sensor responds to high-frequency vibrations of the cylinder, and converts them into electrical signals, the magnitude of which increases with increasing the detonation. Based on these signals, the ECM displaces the ignition timing to the delay side, thereby eliminating detonation.

The temperature sensor in the engine air inlet

The temperature sensor of air entering the engine is a thermistor whose resistance varies with temperature. The ECM allows for the sensor signal and adjusts the pulse width supplied to the nozzle, thereby changing the amount of fuel supplied to the engine cylinders, and the ignition timing changes.

The oxygen sensor

The car is equipped with two oxygen sensors. Depending on the oxygen concentration in the exhaust gas oxygen sensor induces a voltage from 0 to 1 V. On the basis of these data, the engine control unit changes the opening of the injectors and the fuel ratio in the fuel mixture. In order to complete combustion of the combustible mixture and the exhaust gases no harmful substances to 14.7 parts by weight of the air shall have to 1 part of fuel.

Both oxygen sensor equipped with heaters that keep the temperature sensor in a certain range with the engine at all operating conditions. Maintaining a specific temperature sensor enables the system to quickly engage in work and to work in an idling mode.

The front oxygen sensor

Front oxygen sensor located in the exhaust pipe for a catalytic converter and transmits an output signal based on which the ECM determines the oxygen content of the exhaust gases. Based on these data, the engine control unit changes the opening of the injectors.