What is the working principle of the EGR valve?
2 Answers
EGR valve works as follows: 1. The EGR valve stem rises, pushing the connected sliding contact arm to change its position, causing the sliding contact to move along the sliding resistor, generating different voltage signals. These signals are transmitted to the engine control ECU, which monitors the position of the EGR valve to ensure it responds correctly to ECU commands. This adjusts and corrects the opening timing and duty cycle of the EGR valve, precisely controlling the amount of recirculation to reduce emissions and improve performance. 2. EGR stands for Exhaust Gas Recirculation system, and the EGR valve is a key control component in the entire EGR system. The EGR valve is installed on the intake manifold. Exhaust Gas Recirculation (EGR valve) introduces exhaust gases into the intake manifold, reducing the oxygen content in the intake air, thereby lowering combustion temperature and reducing nitrogen oxide emissions. The EGR valve, or Exhaust Gas Recirculation valve, is a mechatronic product installed on diesel engines to control the amount of exhaust gas recirculated back into the intake system.
After all these years of repairing cars, the most common issue with EGR valves is carbon buildup causing them to stick. Simply put, this valve is an exhaust gas recycling switch—it redirects a portion of exhaust gases from the engine's exhaust pipe back into the cylinders to be burned again. Why do this? Because high-temperature combustion in the engine produces nitrogen oxide pollution. The exhaust gas contains no oxygen but retains heat, so mixing it in effectively cools the combustion, similar to adding cold water to a stir-fry to prevent burning. The car's computer controls the valve's opening and closing via a vacuum line or an electric motor. The valve stays tightly shut during cold starts and idling, opens slightly during steady-speed driving, and closes completely during sudden acceleration to allow the engine to deliver full power. Cars frequently driven in urban areas need special attention, as carbon buildup can cause the valve to stick in a mid-position, leading to unstable idling or excessive emissions.
