Valve Timing for Control of Oxides of Nitrogen (NOx)

Three engine camshaft approaches to the reduction of oxides of nitrogen were investigated: increased valve overlap, variable camshaft timing, and variable valve overlap. The interaction of these systems with emissions, fuel consumption, and power was evaluated on a dynamometer engine. The effects of air-fuel ratio and exhaust backpressure were also reported. Results of the dynamometer study were verified with vehicle tests.

Oxides of nitrogen levels of 1.2-2.0 g/mile were attained through camshaft design with acceptable drivability on the 1970 federal test procedure.