The purpose of an EGR valve is to reduce nitrogen oxide emissions in an internal combustion engine. It accomplishes this by recirculating a portion of the engine’s exhaust back into the intake manifold. The EGR valve helps to lower combustion temperatures, which in turn reduces the formation of nitrogen oxide. It can also improve fuel efficiency and engine performance under certain conditions.

An EGR valve can be controlled either mechanically or electronically, depending on the vehicle’s design.

delphi egr valve for SBC V8
Here’s an EGR Valve for a later small block Chevy V8. They don’t all look like this, but from this angle you can see the large diaphragm housing and the valve port. (Image/Delphi)

Benefits of an EGR Valve

In addition to the reduced emissions, an EGR valve can help improve overall combustion efficiency by optimizing the air-fuel mixture in the combustion chamber. By lowering combustion temperatures, an EGR valve can also foster improved fuel economy and prevent engine knock, which can directly lead to enhanced engine longevity.

Where is the EGR Valve Located?

The EGR valve is typically located on or near the intake manifold of the engine, but its exact position can vary depending on the make and model of the vehicle.

Many vehicles have the EGR valve mounted directly on the intake manifold. However, on some engines, it may be located on the exhaust manifold.

Close up of an EGR Valve on an LS! in a 1998 Camaro 2
As an example, the black cylinder in the circle is the top of the EGR valve assembly on an early LS1 found in 4th-gen. Camaro. (Image/OnAllCylinders)

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Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.