The Emission Control Technology Division of the Environmental Protection Agency is interested in engine control techniques that influence emissions and fuel economy. One engine parameter that is readily adjustable is basic ignition timing, and it was desired that data be collected on a variety of late model (1975) vehicles to quantify its effect. Data from such a program would be useful in studies of inventor devices which occasionally include timing adjustments as part of the installation instructions, in tampering studies where investigations are made of the effect of emission control system modification, and in octane requirement problem investigations because of the influence of ignition timing on octane requirements.