6.4.2. Models with 1,6 and 2,0 liter engines
All Nissan Sunny models described in this management can use the gasoline which is not containing tetraethyllead and also, have the systems promoting minimization of harmful emissions in the atmosphere.
On all models the system of decrease in emission of crankcase gases, and also the following systems, depending on model is installed:
Models with the 1,6 liters carburetor engine without catalytic converter – system of decrease in toxicity of exhausts during the operation of the engine in the mode of idling and a damper of a butterfly valve.
Models with the 1,6 liters carburetor engine with the catalytic converter – the catalytic converter, system of recirculation of exhaust gases, the control system behind release of vapors of fuel from fuel system, system of an admission of air, system of decrease in toxicity of exhausts during the operation of the engine in the mode of idling and a damper of a butterfly valve.
Models with the 1,6 liters engine and multipoint system of injection of fuel – the catalytic converter, system of recirculation of exhaust gases and the control system over release of vapors of fuel from fuel system.
Models with the 2,0 liters engine and single-point system of injection of fuel without catalytic converter – system of thermal neutralization of exhaust gases and a damper of a butterfly valve.
Models with the 2,0 liters engine and single-point system of injection of fuel with the catalytic converter – the catalytic converter, system of recirculation of exhaust gases, the control system over release of vapors of fuel from fuel system, system of thermal neutralization of exhaust gases and a damper of a butterfly valve.
Models with the 2,0 liters engine and multipoint system of injection of fuel without catalytic converter – no additional systems of decrease in toxicity of exhausts are installed.
The Phase I models (release till June, 1993) with the 2,0 liters engine and multipoint system of injection of fuel with the catalytic converter – the catalytic converter and the control system over release of vapors of fuel from fuel system.
The Phase II models (release after June, 1993) with the 2,0 liters engine and multipoint system of injection of fuel with the catalytic converter – the catalytic converter, the control system over release of vapors of fuel from fuel system and system of recirculation of exhaust gases.
System of decrease in emission of crankcase gases
For decrease in emission of not burned down hydrocarbons from an engine case in the atmosphere the engine hermetically is closed, and the gases and vapors of engine oil breaking in an engine case get from a case via the valve into the inlet channel from where they, then, will come to the engine and will be burned in the following cycles of operation of the engine.
In case in an inlet collector there is very low depression, gases will just drag on in it from an engine case. When depression in an inlet collector not so big, gases come out an engine case under the influence of higher (relatively) pressure in a case; when the engine is worn-out, the increased pressure in a case (because of increase in break of gases) will force a part of gases to come to an inlet collector with any pressure in a collector.
Catalytic converter
The sensor is sensitive to the content of oxygen in exhaust gases and sends to an electronic control unit signals with various tension depending on its concentration. If the taken-away air / fuel mix is too rich, the sensor sends a signal with high voltage. Tension decreases at increase in content of oxygen in fuel mix. The maximum coefficient of neutralization of the fulfilled gases is reached by the catalytic converter when chemically correct composition of fuel mix / the taken-away air for full combustion of gasoline – 14,7 parts is supported (on weight) air on 1 part of fuel (a stoichiometric ratio). At such ratio, tension of signals of the sensor sharply changes and the electronic control unit respectively regulates composition of fuel mix / the taken-away air, changing the injector(s) impulse duration (time during which the injector is open). On later models in the sensor there is a built-in heating element (controlled by an electronic control unit) which serves quickly to warm up a sensitive tip of the sensor up to the normal working temperature.
The control system over release of vapors of fuel from fuel system
For minimization of emissions of not burned down hydrocarbons in the atmosphere, on models with the catalytic converter the control system over release of vapors of fuel from fuel system is installed. The cap of a jellied mouth of the fuel tank is hermetically closed and the coal filter collects the gasoline vapors formed in the fuel tank (model with fuel injection) or in the fuel tank and the float-operated camera of the carburetor (model with the carburetor engine) when the car stands still. Couples remain in the coal filter until they cannot be let out to the inlet canal during the operation of the engine.
On models with the carburetor engine work of system the thermal vacuum valve which is installed in an inlet collector operates; the thermal vacuum valve, also, operates work of system of recirculation of exhaust gases. When the engine the cold, thermal vacuum valve closes receipt of depression on the vacuum membrane valve of the coal filter and the filter remains is closed. When the engine gets warm up to the normal working temperature (about 70 °C), the thermal vacuum valve opens and the depression which is present at an inlet collector influences a diaphragm of the coal filter. The membrane valve opens also all couples which gathered in the coal filter drag on to the inlet canal with the subsequent combustion in the following cycles of operation of the engine.
On the models "Phase I" (release till June, 1993) with the 2,0 liters engine and multipoint system of injection of fuel the coal filter is connected directly to an inlet collector and work of system the restrictive valve on the vacuum membrane valve of the filter operates. When the engine works, the depression which is present at an inlet collector influences a diaphragm via the restrictive valve. During the operation of the engine in the idling mode the valve is closed, but, at increase in speed of operation of the engine, depression in an inlet collector increases. The restrictive valve increases depression behind a diaphragm, thus, controlling opening of the membrane valve depending on the speed of operation of the engine. The valve is open a little at a low speed of operation of the engine, but opens completely at increase in speed of operation of the engine.
On all models operation of the control system on release of vapors of fuel from fuel system copes an engine electronic control unit via the electromagnetic valve with fuel injection; the same electromagnetic valve operates work of system of recirculation of exhaust gases. In order that the engine correctly worked after cold start and / or in the idling mode, and also for protection of the catalytic converter at receipt in the engine of too rich fuel mix, the electromagnetic valve does not open an electronic control unit until the engine is heated-up or on it loading is not given. After that, the electromagnetic valve opens in order that collected vapors of fuel could get to the inlet channel.
System of recirculation of exhaust gases
This system reduces the content of not burned down hydrocarbons in exhaust gases until they got to the catalytic converter. For this purpose some part of exhaust gases gets from a final collector and is produced back in an inlet collector, through the tube connecting them then they participate in operation of the engine again. The valve of recirculation of exhaust gases is installed that end of a connecting tube which fastens to an inlet collector.
On models with the carburetor engine work of system the thermal vacuum valve and the valve of counter-pressure operates. The thermal vacuum valve, also, controls operation of the control system on release of vapors of fuel from fuel system. When the engine the cold, thermal vacuum valve stops receipt of depression on the recirculation valve, and it remains is closed. When the engine is heated-up up to the normal working temperature (about 70 °C), the thermal vacuum valve opens, allowing depression to influence the recirculation valve via the counter-pressure valve. The valve of counter-pressure is sensitive to pressure of exhaust gases and, according to it, opens or closes the recirculation valve. When pressure of exhaust gases high, the valve of counter-pressure is closed that allows depression to influence the recirculation valve, opening it. When pressure of exhaust gases falls, the valve of counter-pressure opens, stopping receipt of depression on the recirculation valve, the valve is closed.
On models with fuel injection, the system of recirculation of exhaust gases copes an electronic control unit operation of the engine via the electromagnetic valve and the valve of counter-pressure; the electromagnetic valve also operates operation of the control system on release of vapors of fuel from fuel system. When the engine cold, an electronic control unit operation of the engine holds the electromagnetic valve closed, stopping receipt of depression on the recirculation valve. When the engine gets warm up to the normal working temperature, the electronic control unit opens the electromagnetic valve, allowing depression to influence the recirculation valve via the counter-pressure valve. The valve of counter-pressure is sensitive to pressure of exhaust gases and, according to it, opens or closes the recirculation valve. When pressure of exhaust gases high, the valve of counter-pressure is closed that allows depression to influence the recirculation valve, opening it. When pressure of exhaust gases falls, the valve of counter-pressure opens, stopping receipt of depression on the recirculation valve, the valve is closed.
System of thermal neutralization of exhaust gases
This system reduces the content of not burned down hydrocarbons in exhaust gases, without allowing their excessive hit in exhaust gases. It is reached by giving of additional amount of air in an inlet collector when depression in an inlet collector very high. The system turns on only one valve.
The valve of system of thermal neutralization of exhaust gases is sensitive to pressure in an inlet collector. If in an inlet collector too high depression (i.e. when the butterfly valve is closed at a high speed of operation of the engine) is formed, the valve opens and passes in an inlet collector a portion of the fresh filtered air from a casing of the air filter.
System of an admission of air in a final collector
The system of an admission of air in a final collector reduces the content of not burned down hydrocarbons (HC) and carbon dioxide (SO) in exhaust gases, passing a part of the air filtered by the air filter directly in a final collector in order that a considerable part of molecules of not burned down hydrocarbons and carbon dioxide could be oxidized in a final collector before hit in the catalytic converter. The system turns on the valve of air supply and the electromagnetic valve operated by an electronic control unit operation of the engine.
In order that the engine correctly worked after cold start and / or in the idling mode, the electromagnetic valve does not open an electronic control unit until the engine gets warm and on it loading is given. When there come both of these conditions, the electromagnetic valve opens in order that the portion fresh, filtered by the air filter, air could get to a final collector. For an air intake from the air filter the difference between pressure in a final collector and the air filter therefore there is no need to use the air pump for air supply is used. The valve of air supply passes air only in one direction therefore exhaust gases cannot get to the air filter.
System of decrease in toxicity of exhausts during the operation of the engine in the idling mode
The system of minimization of emission of exhaust gases idling of the engine serves in order that fuel mix did not become too rich at high temperature of the engine. It is reached by an admission of additional amount of air in an inlet collector at high temperature of the engine. The system turns on only one valve which is installed on a casing of the air filter.
The valve of system of minimization of emission of exhaust gases idling of the engine has the bimetallic spring sensitive to temperature. At a low temperature of the engine the valve is closed. When temperature increases in a casing of the air filter, the bimetallic spring of the valve is deformed, and the valve gradually opens. It allows fresh, filtered by the air filter, to air to get to an inlet collector that increases the content of oxygen in fuel mix.
Damper of a butterfly valve
The damper of a butterfly valve serves for decrease in content of not burned down hydrocarbons in exhaust gases at switching off of the engine or sharp decrease in turns. It is reached by prevention of sharp closing of a butterfly valve, for example, when the driver at a high speed of operation of the engine quickly releases an accelerator pedal. The damper of a butterfly valve serves as the shock-absorber and slowly closes a butterfly valve at the last stages. It reduces the content of not burned down hydrocarbons in exhaust gases, preventing education in an inlet collector of too big depression that would lead to hit not burned down until the end of fuel in a final collector.