"Introduction The attached report by Automotive Testing Laboratories@ Inc. (ATL)@ of East Liberty@ Ohio@ entitled ""A Study of the Factors Influencing the Evaporative Emissions from In-Use Automobiles@"" fulfilled a contract with the API Gasoline Volatility Task Force. This study was undertaken in response to actions by the Environmental Protection Agency (EPA) and state environmental agencies. Since late 1983@ EPA has been measuring the evaporative emissions of in-use vehicles from the Ann Arbor/Detroit area. Measurements were made using Indolene {the 9.0 psi RVP emission test certification fuel)@ commercial fuel (11.5 psi RVP)/ and a blend of Indol ene and commercial fuel {10.4 psi RVP). Data from these tests formed the basis for EPA's revision of evaporative emission factors in M0BILE2. The MOBILE model is EPA's program for calculating evaporative emissions from mobile sources. The latest program@ cal1ed M0BILE3@ utilizes evaporative emissions developed from EPA??survey of in-use vehicles using 11.4 psi RVP gasoline@ while MOBILES utilized factors from vehicle certification tests using 9 psi RVP gasoline. During the spring of 1984@ M0BILE3 was made available for calculating emissions from vehicles. State environmental agencies are using M0BILE3 to prepare state implementation plans (SIPs) for attainment of the National Ambient Air Quality Standard for ozone. The standard must be attained by December 31@ 1987@ for those areas which had not met the ozone standard before December 31@ 1982. The API task force had several concerns with the data used to develop the evaporative emissions factors in MOBILES: 1. The 1981-1983 model vehicles from the Ann Arbor/Detroit area had a high percentage of defects (30 percent) in their evaporative emissions control systems and a high percentage failed to meet evaporative emissions standards (77 percent). These in-use vehicles may not be representative of the national in-use vehicle f1eet. 2. EPA used a shortened vehicle preconditioning cycle rather than the standard preconditioning cycle in their evaporative emissions testing of in-use vehicles. This shorter cycle had the potential to give higher evaporative emissions . Since these data were used as the basis for evaporative emissions factors in MOBILES@ the model would also predict evaporative emissions values that are too high. 3. EPA applied the same diurnal evaporative emissions factors to both carbureted and fuel injected vehicles (1981 and newer models) even though their limited data showed fuel injected vehicles had lower diurnal emissions. We would expect the fuel injected vehicles to have lower evaporative emissions than carbureted vehicles. The purpose of the API study was to develop information@ using a fleet of vehicles representing the national in-use fleet in 1987@ to address some of our concerns with M0BILE3 and its vehicle data base. The main objectives of this study were to: (1) develop information on the defect and failure rate of in-use vehicles from another locality; (2) develop more information on the differences between fuel injected and carbureted vehicles; (3) eval uate the evaporative emissions response of these vehicles to gasol ine RVP changes; (4) assess the potential benefit of an inspection/maintenance (l/M) program designed to detect evaporative control system defects. (5) compare emissions from vehicles with high odometer mileage to vehicles with low mileage. To address these questions@ a f1eet of forty cars representative of the 1987 national in-use car population was evaluated. The fleet consisted of sixteen (16) 1979-80 vehicles (6 gram/test standard) and twenty-four (24) 1981-83 vehicles (2 gram/test standard). Three fuels were used. They were: (1) Indolene (9.0 RVP); (2) a commercial fuel blended with Indolene to approximate the 11.5 RVP fuel used by EPA (11.8 RVP); and (3) a 50-50 blend of these two fuels (10.4 RVP). For convenience@ the analysis and discussion which follows only refers to the fuels by their RVP values; 9.0@ 10.4@ and 11.8."
API PUBL 4406-1985 history
1985API PUBL 4406-1985 A Study of Factors Influencing The Evaporative Emissions From In-Use Automobiles