Reduction of Nitrogen Oxides in Automobile Exhaust

Although the control of nitrogen oxides from automobile exhaust is not yet required by law, several methods have been investigated to determine how much control is possible and what penalties result. These methods involved spark timing, carburetion, and exhaust recirculation. On one test car, a control system was developed which reduced nitrogen oxides 74% while maintaining hydrocarbon and carbon monoxide control at current (1968) federal levels. However, a 13% loss in fuel economy was incurred, and driveability problems were observed. Application to other car models, deposit accumulation, durability, and performance under extreme weather conditions are all open questions at this time.