- fuel supply system, including fuel tank, electric fuel pump module, pipelines, hoses, fuel rail with injectors and fuel pressure pulsation compensator;
- an air supply system consisting of an air filter, an air supply hose and a throttle assembly;
- fuel vapor recovery system, including an adsorber, an adsorber purge valve and connecting pipelines.
The functional purpose of the fuel supply system is to ensure the supply of the required amount of fuel to the engine in all operating modes. The engine is equipped with an electronic control system with distributed fuel injection. In the distributed fuel injection system, the functions of mixture formation and metering of the fuel-air mixture supply to the engine cylinders are separated: the injectors perform metered fuel injection into the intake pipe, and the required amount of air at each moment of engine operation is supplied by the throttle unit. This control method makes it possible to ensure the optimal composition of the combustible mixture at each specific moment of engine operation, which allows for maximum power with the lowest possible fuel consumption and low toxicity of exhaust gases. The fuel injection system and the ignition system are controlled by the electronic engine control unit, which continuously monitors the engine load, vehicle speed, engine thermal state, and the optimality of the combustion process in the cylinders using appropriate sensors.
The peculiarity of the injection system of the Ford Focus II is the synchronicity of the injectors' operation in accordance with the valve timing (the engine control unit receives information from the phase sensors). The controller switches on the injectors sequentially, and not in pairs, as in asynchronous injection systems. Each injector is switched on after 720° of crankshaft rotation. However, in starting modes and dynamic engine operation modes, an asynchronous fuel supply method is used without synchronization with the crankshaft rotation.
The main sensor for the fuel injection system is the exhaust gas oxygen concentration sensor (lambda probe). In the exhaust manifold of the R4 16V Duratec Ti-VCT engine, combined with the exhaust gas neutralizers (catalytic manifold), two oxygen concentration sensors are installed (separately for the exhaust tracts of the 1st and 4th, 2nd and 3rd cylinders), which, together with the engine control unit and injectors, form a control circuit for the composition of the fuel-air mixture supplied to the engine. Based on the sensor signals, the engine control unit determines the amount of unburned oxygen in the exhaust gases and, accordingly, evaluates the optimality of the fuel-air mixture entering the engine cylinders at each moment in time. Having recorded a deviation of the composition from the optimal 1:14 (fuel and air, respectively), ensuring the most efficient operation of the exhaust gas catalytic neutralizers, the control unit changes the mixture composition using the injectors. Since the oxygen concentration sensors are included in the feedback circuit of the engine control unit, the control circuit for the air-fuel mixture composition is closed. A special feature of the engine control system of the Ford Focus II is the presence, in addition to two control sensors, of two more diagnostic oxygen concentration sensors installed at the outlet of the neutralizers. Based on the composition of the gases that have passed through the neutralizers, they determine the efficiency of the engine control system. If the engine control unit, based on the information received from the diagnostic oxygen concentration sensors, records an excess of the exhaust gas toxicity standard that cannot be eliminated by calibrating the control system, it turns on the engine malfunction indicator lamp in the instrument cluster and stores the error code in memory for subsequent diagnostics.
Fuel tank, molded from special impact-resistant plastic, is installed under the body floor in its rear part and secured with clamps. To prevent fuel vapors from entering the atmosphere, the tank is connected by a pipeline to the adsorber of the fuel vapor recovery system. An electric fuel pump is installed in the flange opening in the upper part of the tank, and on the right side there are branches for connecting the filler pipe and ventilation hose. From the pump, which includes coarse and fine fuel filters, fuel is fed into the fuel rail, secured to the engine intake pipe. From the fuel rail, fuel is injected by injectors into the intake pipe.
Fuel lines combined power supply systems, in the form of interconnected steel pipelines and rubber hoses.
Fuel pump submersible, electric-driven, rotary type, with coarse and fine fuel filters, with a fuel pressure regulator. The pump is installed in the fuel tank, which reduces the possibility of vapor locks, since the fuel is supplied under pressure, and not under vacuum. The fuel pump supplies fuel from the fuel tank through the fuel line to the fuel rail under a pressure of about 380 kPa (approximately 360 kPa in idle mode).
Fuel filter fine cleaning - full-flow, installed in the fuel pump module housing. If the filter is clogged, it is necessary to replace the housing together with the filter, since the unit is non-separable.
Fuel rail 5 (Fig. 5.26), which is a hollow tubular part with holes for installing injectors 8 and a compensator 2 for fuel pressure pulsations, serves to supply fuel to the injectors and is secured to the inlet pipe. The injectors and the compensator for pressure pulsations are sealed in their sockets with rubber rings 3, 4 and 7. The ramp with the injectors in assembly is inserted with the tails of the injectors into the holes of the inlet pipe and secured with two nuts.
Fig. 5.26. Fuel rail with injectors and fuel pressure pulsation compensator: 1 – fuel pressure pulsation compensator mounting bolts; 2 – fuel pressure pulsation compensator; 3 – fuel pressure pulsation compensator sealing rings; 4 – upper injector sealing rings; 5 – fuel rail; 6 – injector retainers; 7 – lower injector sealing rings; 8 – injectors
NOTE: Depending on the version, the fuel pulsation compensator may not have a small O-ring.
Nozzles 8 (see Fig. 5.26) enter the inlet pipe openings with their sprayers. In the inlet pipe openings, the sprayers are sealed with rubber sealing rings 7. The sprayer is designed for metered injection of fuel into the engine cylinder and is a high-precision electromechanical valve in which the shut-off valve needle is pressed against the seat by a spring. When an electrical impulse is applied from the control unit to the electromagnet winding, the needle rises and opens the sprayer opening - fuel is supplied to the engine inlet pipe. The amount of fuel injected by the sprayer depends on the duration of the electrical impulse.
Fuel pressure pulsation compensator is installed at the end of the fuel rail and serves to maintain constant fuel pressure in the rail when there is a sharp drop in the fuel line, caused, for example, by a significant increase in fuel consumption during intensive acceleration of the vehicle.
Air filter is installed on the left side of the engine compartment on a special bracket. The filter element is paper, flat, with a large filter surface area. The filter is connected by a rubber corrugated air supply sleeve to the throttle assembly.
The pipe in the lower part of the filter housing is installed with tension into the neck of the intake noise muffler, located under the left front wing of the car.
Throttle assembly, which is the simplest control device, serves to change the amount of main air supplied to the engine intake system, is installed on the inlet flange of the intake pipe and secured with screws. A molded rubber sleeve is put on the inlet pipe of the throttle assembly, secured with a clamp and connecting the throttle assembly with the air filter.
The throttle assembly includes a throttle position sensor and a stepper motor for controlling the throttle valve. There is no mechanical connection between the throttle assembly and the throttle valve control pedal. The so-called "electronic" throttle valve control pedal transmits information about the degree of pressure on the pedal to the electronic engine control unit, which, in turn, taking into account the vehicle speed, the gear engaged, the engine load and the crankshaft speed, opens the throttle valve to the required angle.
Fuel vapor recovery system prevents fuel vapors from escaping from the fuel system into the atmosphere, which have an adverse effect on the environment.
The system uses a method of vapor absorption by a carbon adsorber. It is installed in the rear part of the body base and is connected by pipelines to the fuel tank and the purge valve.
In the engine compartment, on the intake pipe, there is an electromagnetic valve for purging the adsorber, which switches the operating modes of the system based on signals from the engine control unit.
Fuel vapors from the fuel tank are constantly removed through the pipeline and accumulate in the adsorber filled with activated carbon (adsorbent). When the engine is running, the adsorbent is regenerated (restored) by purging the adsorber with fresh air entering the system under the action of vacuum transmitted through the pipeline from the inlet pipe to the adsorber cavity when the purge valve is opened. The control unit regulates the degree of purge of the adsorber depending on the engine operating mode, sending a signal with a variable pulse frequency to the valve.
Fuel vapors from the adsorber enter the engine intake pipe through a pipeline and burn in the cylinders.
Malfunctions of the fuel vapor recovery system lead to unstable idle speed, engine stalling, increased toxicity of exhaust gases and deterioration of the vehicle's driving performance.