Performance of a Fixed Volume Open-Loop Mini SHED System for Evaporative Emissions Testing

This paper presents the use of a fixed volume, open-loop (FVOL) mini SHED (Sealed Housing for Evaporative Determination) for the measurement of evaporative emissions of fuel systems components. Because of tighter government emissions standards for vehicles, more stringent requirements are being made for emissions testing at the component level. Component suppliers need to provide accurate and repeatable emissions test data as well as more extensive testing to show compliance with customer requirements. In light of these demands, improving accuracy and reducing costs for component emissions testing is becoming more important. In this paper, we present a method for using open-loop sampling in conjunction with a fixed volume mini SHED system for emissions testing of automotive components. The advantage of this system is improved accuracy at reduced cost. We also present a simple method for validation of SHEDs using fuel based hydrocarbon vapors. This method provides a more accurate measure of SHED performance than the standard propane validation.