Tuesday, September 24, 2013
EGR Valve Types
Exhaust gas recirculation valves, better known as EGR valves, minimize your car engines creation of nitrous oxide, which can be harmful to the environment. EGR valves play a crucial part in cutting down on the creation of smog. EGR valves help to reduce the overall temperature of the engine by introducing a portion of exhaust gas back into the combustion chambers. The exhaust gas takes the place of otherwise combustible material (air and gasoline), thereby causing cooler combustion temperatures while still generating the same force to push the piston. EGR valves can reduce smog creation by as much as 60 percent. Several major types of EGR valves exist.
Single Diaphragm EGR Valves
Single diaphragm EGR valves are the oldest and simplest type of EGR valve. They consist of a spring-loaded diaphragm connected to a pintle and seat by a slender steel shaft. Vacuum is ported into the diaphragm, which causes the pintle to pull off of its seat. The removal of the pintle from its seat results in the exhaust being allowed to flow into the valve chamber and the intake manifold.
Positive Back Pressure EGR Valves
Positive back pressure EGR valves have a much thicker pintle shaft than a single diaphragm valve. They also usually have a "P" stamped next to the part number and date code. The pintle shaft on these EGR valves is hollow, and it is the play between this hollow control valve and a control valve that regulates vacuum flow that causes the valve to work. Exhaust gases flow into the shaft itself and push up on the shaft, which it turn seals the built-in control valve. Vacuum pressure pulls on the diaphragm and causes it to open.
Negative Back Pressure EGR Valves
Negative back pressure EGR valves can be identified by the "N" stamped next to the date and the part number. It looks very similar to a positive back pressure EGR valve. This EGR valve is opened by a combination between applied engine vacuum and negative exhaust system impulses. When the pintle opens, back pressure is reduced. This reduction causes the control valve vacuum bleed to open and a valve to close. The negative exhaust pulses help to regulate the flow of gas.
Integrated Electronic and Mechanical EGR Valves
An integrated electronic and mechanical valve can be identified by its single vacuum source inlet and three-wire electrical connector. Its basic operation is similar to a single diaphragm EGR valve except for a small pintle position sensor atop its diaphragm. This sensor communicates with the power control module, which in turn applies vacuum when necessary by signaling a pulse width modulated solenoid.
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