Effectiveness of Exhaust Gas Recirculation With Extended Use

Exhaust gas recirculation (EGR) was found to be an effective means of reducing automotive NO_x levels with no major unsolvable problems over 52,000 miles under city/suburban driving conditions. Compatible with air injection and engine modification systems for HC and CO control, EGR effectively reduced the NO_x levels with no decrease in reduction over the 52,000 miles. Engine wear and engine cleanliness with EGR was normal for the mileage and driving regime. However, the throttle area and exhaust valves were found to be sensitive to leaded fuels.