![]() The gas is then passed back to the inlet manifold via a pipe. A secondary valve is also used to help create a vacuum in the inlet manifold as this is not naturally present on diesel engines.ĭiesel Low pressure EGR valves divert the exhaust gas after it has passed through the diesel particulate filter - this gas has a lower flow but is almost completely clean of soot. The gas is then passed back to the inlet manifold either via a pipe or internal drillings in the cylinder head. Types of EGR valveĪlthough there are several types of EGR valve - earlier systems use a vacuum-operated valve, while newer vehicles are electronically controlled - the main types can be broadly summarized as:ĭiesel high pressure EGR valves divert the high-flow, high-soot exhaust gas before it enters the diesel particulate filter – the soot can combine with the oil vapor to create sludge. In diesel, it can also help to reduce diesel knock at idle. However as more torque and power is required, for example during full acceleration, the EGR valve closes to ensure as much oxygen enters the cylinder.Īs well are reducing NOx, EGR valves can be used in downsized GDi engines to reduce pumping losses and improve both combustion efficiency and knock tolerance. During idle and at low speeds, only a small amount of power is required, and therefore only a small amount of oxygen, so the valve gradually opens – it can be up to 90% open at idle. The EGR valve is closed when the engine is starting up. The EGR valve has two primary settings: open and closed, although the position can vary anywhere in between. With less oxygen, the now diluted mixture burns slower, lowering temperatures in the combustion chamber by almost 150☌, and reducing NOx production for a cleaner, more efficient exhaust. ![]() To help minimize this, the EGR valve allows a precise quantity of exhaust gas to re-enter the intake the system, effectively changing the chemical makeup of the air entering the engine. However, when it is exposed to the extremely high temperatures in the combustion chamber, plus 1370☌, the normally inert gas becomes reactive, creating harmful oxides of nitrogen or NOx, which are then passed through the exhaust system into the atmosphere. ![]() Nearly 80 percent of the air we breathe is nitrogen. Examples of harsh environments for EGR valves.
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