Search Results

The CO2 tracer technique is a method of measuring automotive exhaust mass emissions during arbitrary modes of operation of a car on the 1972 federal emission test driving schedule. This technique allows modal mass measurements of low-emission cars based on undiluted exhaust gas concentrations. The CO2 concentration at the tailpipe is compared with the CO2 in the diluted stream to obtain exhaust flow. This flow, multiplied by tailpipe concentrations of hydrocarbon, carbon monoxide, and nitric oxide, and integrated over the driving mode, gives modal mass emissions. Problems associated with the lag between the time at which a transient maneuver takes place in the engine and the time at which measurements are recorded are also discussed.

Cars with engines having low combustion chamber surface area in relation to volume have correspondingly low exhaust hydrocarbon concentration on the California Schedule. Combustion chamber surface area relative to volume increases with compression ratio and number of cylinders, and it decreases with long stroke and larger displacement.

A method has been developed to estimate from engineering tests the fuel economy that will be observed by customers in normal car service. Trip length, horsepower, weight, temperature, and type of driving are used to predict customer fuel economy.