The Relation Between Knock and Exhaust Emissions of a Spark Ignition Engine

The effect of knock intensity on exhaust emissions was examined in a single cylinder spark ignition engine. The exhaust components surveyed were carbon monoxide, carbon dioxide, oxides of nitrogen (as NO), and total unburned hydrocarbons. Knock was induced solely by changing the spark timing. To describe knock intensity quantitatively, the magnitudes of the rate of pressure irregularities occurring during the combustion process were utilized. The use of the rate of pressure change to define a quantitative knock intensity scale is supported by an apparent generalization of the stoichiometric air-fuel ratio data. Graphs are presented that indicate the dependency of power output as well as exhaust emissions on knock intensity for various air-fuel ratios.