A running loss test procedure has been developed which integrates a point-source collection method to measure fuel evaporative running loss from vehicles during their operation on the chassis dynamometer.
The point-source method is part of a complete running loss test procedure which employs the combination of site-specific collection devices on the vehicle, and a sampling pump with sampling lines. Fugitive fuel vapor is drawn into these collectors which have been matched to characteristics of the vehicle and the test cell. The composite vapor sample is routed to a collection bag through an adaptation of the ordinary constant volume dilution system typically used for vehicle exhaust gas sampling.
Analysis of the contents of such bags provides an accurate measure of the mass and species of running loss collected during each of three LA-4* driving cycles.
Other running loss sampling methods were considered by the Auto-Oil Air Quality Improvement Research Program (AQIRP or Program). These included the longstanding but rarely used adsorptive carbon traps technique or the use of dry ice for vapor condensation. Considered also was the use of the SHED** running loss measurement method combining the vehicle and driver on the dynamometer sealed within an enclosure (SHED) which, for the Program, posed timing, implementation, operational safety, and cost concerns.