Surveys of smog forming pollutants from the exhaust of the California car population have shown a tremendous range of emissions between the worst and the best cars. The California MVPCB conducted a study at Scott Research Laboratories to determine the effectiveness and cost of various tune-up approaches to the auto exhaust emission problem.
Four phases of tune-up were explored and pertinent facts and data are included in this paper. Three major engine systems affecting emissions of older cars are ignition, carburetion, and exhaust valve leaks. Exhaust control is predicted to be a $150,000,000 annual business and the incentive exists to develop more effective and cheaper control systems.