Fuel Tank Running Losses – A Pre-Control Evaporative Emission Baseline

Prior to nationwide installation of evaporative emission controls in 1971, a significant quantity of hydrocarbon vapors was lost from fuel tank vents during vehicle operation. Earlier published quantifications of that emission source mode were based on test protocols which predated and differed significantly from the now well established 1975 Federal Test Procedure for regulatory emission measurement. This paper reports the results of a series of running loss evaporative emission tests on a fleet of 1970 cars. The testing was designed to provide experimental data under conditions consistent with the regulatory test. Uncontrolled baseline values of 6.7 g (0.9 g/mi) for 1970 cars and 6.0g (0.8 g/mi) for 1960 cars are consequently proposed as benchmarks from which to measure the extent of evaporative emission control accomplished by today's automobiles