Emissions from Heavy Duty Vehicles before and after Tune-up

Exhaust emissions of hydrocarbons, carbon monoxide and oxides of nitrogen from a large sample of model year 1959 thru 1977 gasoline powered heavy duty vehicles were measured. Chassis dynamometer driving cycle measurements were made with laboratory grade instrumentation, and idling measurements were made with inspection-station-type instruments. Emissions were measured and fuel economy calculated with the vehicles in as-received condition and also after their engines were tuned to manufacturers’ specifications. The results should be useful for planning or evaluating heavy duty emissions control programs.