I understand that recirculated exhaust gas in the cylinder takes the place of air and reduces cylinder pressure and heat. Lowering temps cuts down on NOx formation. Does this reduction in temps cause more incomplete combustion? Would less efficient combustion not lead to more CO and VOC production? It just seems to me like EGR would be cutting down NOx levels, but increasing VOC, HC, and CO levels. I know this can't be true otherwise 98-00 fbodies wouldn't have it. Can anyone please help me understand.

 

EGR is only activated under driving conditions that produce higher than "normal" combustion chamber temps. The EGR just brings the temps back to "normal"..... not down so low that it affects the HC oxidation reactions.