Spark Ignition Engine Control Variables Study

Systematic testing of a fuel injected 429 in³ (7.03 dm³) V-8 engine at steady states produced data from which the effects on emissions of three control variables in combination could be determined. Plotted data of brake specific nitric oxide, hydrocarbons, and carbon monoxide, as well as brake specific fuel consumption, are presented as a function of air-fuel ratio, ignition timing, and percent of exhaust gas recirculation (EGR). Analysis of trends shows that EGR permits nitric oxides control with less fuel consumption penalty than extreme rich operation alone. Nitric oxide control is shown to be important at low power levels as well as high, while hydrocarbons are much more of a problem at the lowest power levels than at high engine outputs. An optimum engine size for the weight of a vehicle is indicated. Simulation of warm engine emission tests permits comparisons between several control approaches, suggesting entirely different calibrations are indicated for different emission performance goals.