Operating Modes of the System

GENERAL INFORMATION.

The ECU controls fuel metering to the engine based on the signals of several sensors. The ECU supports several operating modes

of the MPI system, which are described below.

Engine Starting Mode

When the ignition is switched on, the ECU runs the fuel pump for two seconds to build up pressure in the fuel system. At the same time, the ECU processes signals from the engine coolant temperature (ECT) sensor and the throttle position (TP) sensor and calculates the air-fuel mixture required to start the engine.

The air-fuel mixture ratio depends on the engine coolant temperature and

can vary from 1:1.5 at –36 °C to 1:14.7 at 94 °C. The ECU regulates the amount of

fuel supplied to the intake manifold by changing the duration of the opening and closing of the

injector valves. To control the electromagnetic

injectors, an alternating voltage electrical signal is used.

Cylinder Purge Mode

When the air-fuel mixture is strongly enriched and engine starting is difficult, the ECU

enables cylinder purging to remove excess fuel and

dry the spark plugs. When the throttle is fully open and engine speed drops to approximately 400 rpm, the ECU stops fuel supply. If the throttle is slightly closed (throttle opening

must not exceed approximately 80%), the ECU returns the MPI system to engine starting mode.

Operating Mode

The operating mode has two variations. The ECU can control the MPI

in closed-loop or open-loop feedback control.

OPEN LOOP

When the engine is started and crankshaft speed exceeds 400 rpm, the system switches to open-loop operation. In this mode, the ECU meters fuel

based only on the ECT and MAP sensor signals. The HO2S signal is not considered. The ECU maintains open-loop operation until the

following conditions are met.

1) The HO2S signal voltage begins to change, indicating that the sensor has heated up to operating temperature.

2) The ECT sensor signal reaches the threshold temperature value.

3) A specified time has elapsed after engine start.

CLOSED LOOP

The specific values of the parameters listed above depend on the engine model and are

stored in the ECU ROM. When all conditions are met, the ECU switches to control of the

MPI in closed-loop mode. In this mode, fuel metering, determined by the

injector opening duration, is based on the HO2S signal from the exhaust gases, which allows the ECU to maintain the

air-fuel mixture close to the optimal value of 1:14.7.

Acceleration Mode

The ECU responds to a rapid increase in throttle opening angle and airflow speed in the intake manifold by increasing fuel supply.

Deceleration Mode

The ECU responds to a decrease in throttle opening angle and airflow speed in the intake manifold by reducing fuel supply.

When the accelerator pedal is released very quickly, the ECU may completely cut off fuel supply to the engine for a short time.

Battery Voltage Compensation Mode

When battery voltage drops, the ECU compensates for the

reduced spark energy between the spark plug electrodes by: – increasing the injector opening duration.

– increasing idle speed.

– adjusting ignition module operation to increase spark energy.

Fuel Cut-Off Mode

When the ignition is switched off, the ECU completely stops fuel supply. This prevents the engine from running on after ignition is switched off. Fuel supply is also stopped when there are no signals from the ignition module, which

indicates that the crankshaft is stationary. This prevents

excess fuel from entering the engine and disrupting normal operation of the

spark plugs.