Exhaust Gas Recirculation

Published November 6, 2006

This photo shows the EGR valve for the Insight's internal combustion engine. The EGR system is designed to reduce NOx. EGR stands for Exhaust Gas Recirculation and works by routing exhaust gas (which is inert having already been burned) into the intake. The inert gas in the combustion chamber reduces combustion chamber pressures and temperatures. High combustion chamber pressures and temperatures cause high NOx, so by reducing them, NOx is also reduced. Most non-hybrid cars also have EGR systems. Most EGR valves are actuated with a vacuum signal modulated by the engine control computer or an exhaust backpressure modulator. This EGR valve is electronically controlled and and monitored. I've heard American cars have been using this type of valve for a while, but it's relatively new for Japanese cars. Many of the newer Hondas now have a similar EGR valve.