Enabling Flex Fuel Vehicle Emissions Testing – Test Cell Modifications and Data Improvements

The challenges of flex-fuel vehicle (FFV) emissions measurements have recently come to the forefront for the emissions testing community. The proliferation of ethanol blended gasoline in fractions as high as 85% has placed a new challenge in the path of accurate measures of NMHC and NMOG emissions. Test methods need modification to cope with excess amounts of water in the exhaust, assure transfer and capture of oxygenated compounds to integrated measurement systems (impinger and cartridge measurements) and provide modal emission rates of oxygenated species. Current test methods fall short of addressing these challenges. This presentation will discuss the challenges to FFV testing, modifications made to Ford Motor Company’s Vehicle Emissions Research Laboratory test cells, and demonstrate the improvements in recovery of oxygenated species from the vehicle exhaust system for both regulatory measurements and development measurements. A series of recovery experiments were conducted using controlled injections of known masses of ethanol into vehicle exhaust systems. Results show that heating exhaust sample lines and pre-dilution transfer tubes enable increases in recovery and the use of FTIRs with appropriately designed sampling systems. Modal measurements of cold-start emissions show dramatic improvements with heated systems and provide much needed insight to product development engineers/calibrators. Finally, modifications to impinger/cartridge sampling have improved recovery from ~50% to near 100% while requiring little change to operator standard procedures.