What's wrong with Ford Transit EGR control card in the open position?

EGR valve is a mechatronics product installed on gasoline engine, which is used to control the amount of exhaust gas recirculation fed back to the intake system. It is usually located on the right side of the intake manifold, near the throttle body, and connected to a short metal pipe leading to the exhaust manifold. Its function is to control the amount of exhaust gas entering the intake manifold and make a certain amount of exhaust gas flow into the intake manifold for recycling. EGR valve is a very important and key component in exhaust gas recirculation device. EGR valve is divided into mechanical type and electronic control type, and the mechanical type is shown in the right figure. EGR valve can reduce the temperature of the combustion chamber, improve the working efficiency of the engine, improve the combustion environment, reduce the burden of the engine, effectively reduce the emission of NO compounds, reduce knock and prolong the service life of various components by introducing the exhaust gas discharged from engine combustion into the intake manifold.

Exhaust gas recirculation [1] system is used to reduce the emission of nitrogen oxides (NOX) in exhaust gas. Nitrogen and oxygen can only react chemically at high temperature and high pressure, and the temperature and pressure in the combustion chamber of the engine meet the above conditions, especially during forced acceleration. When the engine is running with load, the EGR valve is opened, so that a small amount of exhaust gas enters the intake manifold and enters the combustion chamber together with the combustible mixture. When idling, the EGR valve is closed and almost no exhaust gas is recirculated to the engine. Automobile exhaust is a non-combustible gas (excluding fuel and oxidant) and does not participate in the combustion of the combustion chamber. It reduces the combustion temperature and pressure by absorbing part of the heat generated by combustion, thus reducing the generation of nitrogen oxides. The amount of exhaust gas entering the combustion chamber increases with the increase of engine speed and load.

Exhaust gas recirculation is a method of introducing a part of exhaust gas into the inhaled fresh air (or mixed gas) and returning it to the cylinder for recirculation and combustion during engine operation, which is used to reduce the emission of nitrogen oxides. Nitrogen oxides are a kind of gas that is extremely harmful to human body, and are mainly produced under high temperature and oxygen-enriched conditions. When the engine is working, if part of the exhaust gas is introduced into the cylinder in time and in a proper amount, due to the large specific heat capacity of the main component CO2 in the exhaust gas, the exhaust gas can absorb part of the heat generated by combustion and take it out of the cylinder, thus diluting the mixed gas to a certain extent, thereby reducing the maximum temperature and oxygen content of engine combustion, thereby reducing the amount of nitrogen oxide compounds generated.

However, excessive exhaust gas recirculation will affect the normal operation of the engine, especially at idle speed, low speed and light load. When the engine is running in a cold state and full load (full throttle) requires engine power, the recycled exhaust gas will have a serious impact on the performance of the engine. Therefore, the amount of exhaust gas involved in recirculation should be automatically adjusted according to the actual working conditions and working conditions of the engine. Practice has proved that it is appropriate to change the amount of exhaust gas involved in recirculation between 6% and 13% according to the different engine structures.

In order to avoid the excessive influence of exhaust gas recirculation on engine performance, modern electronically controlled engines also adopt closed-loop control strategy for exhaust gas recirculation, and install EGR valve position sensor at the exhaust gas recirculation valve (some vehicles also adopt exhaust gas temperature sensor or pressure sensor) to carry out closed-loop correction feedback control for actual exhaust gas recirculation.