Description of emission control systems (Mondeo 1 and 2)

1. On models with 4-cylinder engines, the main components of this system are: an oil separator mounted on the cylinder block at the front (from the radiator side), and a positive crankcase ventilation valve mounted in a rubber bushing in the upper part of the oil separator. The piping part of the system consists of a pipe with two flexible hoses (to connect the positive crankcase ventilation valve to the fitting on the left edge of the intake manifold) and a hose connecting the cylinder head cover to the air cleaner (see Fig. 2.1,a). Models with V-shaped 6-cylinder engines have a similar system, but the oil separator is mounted on the cylinder block at the top, between the cylinder heads (see Fig. 2.1,b). A small sponge filter installed in the air cleaner prevents dirt from being sucked into the engine.





2. The system components are designed to reduce the emission of unburned hydrocarbon particles from the crankcase, as well as to reduce the amount of oil sludge formed. Due to the vacuum created in the crankcase, in most operating modes (and in particular at idle), oil vapors and gases that have broken through into the crankcase are sucked out of it. (Air is also forced into the system.) Through the oil separator, these products enter the intake tract for subsequent combustion in the engine.

Fuel Evaporative Control System (FECS)

3. This system is designed to reduce the level of penetration of unburned hydrocarbons into the atmosphere. To concentrate gasoline vapors formed in the tank while the car is parked, a carbon adsorber is installed under the tank, and a sealed cap is installed on the fuel tank neck. During engine operation, vapors leave the adsorber through a purge valve controlled by the ECU into the intake tract for subsequent combustion in the engine.

4. During engine warm-up and/or idle mode, the purge valve does not open to prevent an over-rich mixture from entering the catalytic converter and to ensure normal engine operation. When the engine is warmed up and operating in partial load mode, the purge valve periodically opens and closes to allow gasoline vapors to pass into the intake tract.

Exhaust Gas Recirculation (EGR) system

5. To reduce the content of nitrogen oxides in the exhaust, part of the exhaust gases enters the intake manifold through the EGR valve. Due to this, the combustion temperature decreases.

6. The system contains the EGR valve, the exhaust gas differential pressure sensor, the EGR electromagnetic valve, the ECU and various sensors. The ECU opens the EGR valve at the optimum moment for each operating mode. On models with V-shaped 6-cylinder engines, the EGR system valve is installed on the engine compartment bulkhead (see Fig. 2.6).

Fuel afterburning system

7. This system contains an "air injection" valve installed in the filter housing, a solenoid valve, and a pipeline. The system is designed to inject filtered air directly into the exhaust ports. The engine sucks in air coming out of the filter housing due to the difference in exhaust gas pressure. The air flow enters the exhaust tract only if its pressure is lower than atmospheric. To prevent exhaust gases from getting back into the filter, the "air injection" valve allows the flow in only one direction.

8. The main task of the system is to increase the temperature of the exhaust gases at startup so that the oxygen sensor and catalytic converter quickly warm up to operating temperature. Until this moment, the system reduces the release of unburned hydrocarbons and carbon monoxide contained in the exhaust gases after combustion, due to the fact that a significant part of these substances burns in the manifold itself or in the catalytic converter.

9. The system operates only during engine warm-up, when the oxygen sensor does not affect the air-fuel mixture ratio. The ECU controls the system via an electromagnetic valve.

Catalytic converter

10. The exhaust gases of a gasoline engine contain harmful substances: carbon monoxide, unburned hydrocarbons, nitrogen oxides, a small amount of a solid phase substance containing tiny particles of lead.

11. These substances are harmful to the environment.

12. A catalytic converter is designed to neutralize the vehicle's exhaust. It is installed in the exhaust system and contains noble metals - platinum, palladium or rhodium, which are catalysts that accelerate the reaction between harmful emissions and oxygen. Carbon monoxide is oxidized to dioxide, and hydrocarbons are converted into water. In a three-phase catalytic converter, some of the nitrogen oxides are converted into nitrogen.

Note: The catalytic converter is not a filter. It also does not participate in the chemical reaction, but only accelerates it.

13. The converter contains an element (made of cellular ceramics) covered with a composition of noble metals. It has a developed surface washed by the exhaust gas flow. The element is installed in a stainless steel housing. A two-fraction catalytic converter performs simple oxidation. It neutralizes only carbon monoxide and hydrocarbons. A three-fraction converter neutralizes carbon monoxide, hydrocarbons and nitrogen oxides. Three-fraction converters are divided into uncontrolled (without feedback), which neutralize from 50 to 70% of harmful substances, and controlled (with feedback), which neutralize over 90% of harmful substances.

14. The catalytic converter installed on the Ford Mondeo vehicle presented in this manual is a three-fraction, controlled (with feedback).

Oxygen sensor

15. The sensor installed in the exhaust system provides the ECU with a continuous feedback signal. This allows the mixture composition to be adjusted to ensure optimal operation of the catalytic converter.

16. The sensor has a built-in heating element controlled by the ECU, which allows it to quickly reach the operating temperature mode. The sensor tip is sensitive to oxygen. The sensor sends a voltage signal depending on the oxygen content in the exhaust gases. If the air-fuel mixture is too rich, the exhaust gases contain little oxygen, the sensor sends a low voltage signal. The voltage increases when the mixture is lean and the amount of oxygen in the exhaust gases increases. Optimum conversion of the main components of combustion products occurs when the air/fuel mixture ratio is maintained at a certain level, at which complete combustion of gasoline occurs. This ratio of components is called stoichiometric and corresponds to an air/fuel ratio (by weight) of 14.7:1. Near the critical point, the output voltage signal of the sensor changes sharply. The ECU uses the change in signal as a reference point and accordingly changes the air-fuel mixture ratio by changing the opening duration of the fuel injectors.

Exhaust Gas Differential Pressure Sensor

17. The sensor registers the difference in exhaust gas pressure at the point of narrowing of the exhaust gas recirculation system pipeline. It sends a voltage signal to the ECU depending on the pressure difference.

For details, please visit the website FORDBOOK.RU