what does it do???

[PRS]

What exactly does the EGR valve do, ?? I have read somewhere that it can be beneficial to modify this so that it takes its air from the air cleaner rather than from the exaust manifold, what is the opinion of the experts...??

Peter

 

[MikeC]

(Stolen from a web page)
The EGR stands for Exhaust Gas Recirculation. Exhaust gas is routed back into the combustion chamber to make emissions meet anti-pollution regulations.

EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx).

During normal combustion, Nitrogen(N2), Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combine to form water (H2O) Carbon Dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen Dioxide (NO2). In the presence of sunlight, it combines with other compounds like Hydrocarbons and forms Smog.

Since exhaust gas won't burn, if it's re-introduced into the combustion chamber, it will lower combustion chamber temps enough so that the Nitrogen doesn?t react with the other compounds and is passed unchanged out the tailpipe thus not contributing to smog.

The downside is that exhaust gas doesn?t exactly help with combustion.

At higher RPM?s, this really isn?t noticable, but at idle, the reintroduction of exhaust gas will cause a very rough idle and can cause stalling if too much is fed back into the combustion chamber.

Mike

 

[PRS]

egr

Thanks Mike