Research Projects

Project at a Glance

Project Status: complete

Title: Characterization of particulate emissions from gasoline-fueled vehicles.

Principal Investigator / Author(s): Norbeck, Joseph M

Contractor: UC Riverside

Contract Number: 94-319

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


This two-phase program was designed to (1) increase our knowledge of particulate emission rates from gasoline-fueled vehicles representative of the modem fleet, (2) provide a characterization of the size distribution and chemical composition of these emissions and (3) assess the effects of vehicle operating condition, driving cycle, and fuel type on particulate emission rates. Phase 1 examined the effects of three variables on particulate emissions and composition: driving cycle (Federal Test Procedure (FTP) vs. Unified Cycle (UC)), fuel effects tire-1992 California average gasoline and California Phase 2 reformulated gasoline (RFG)), and vehicle technology (three-way catalyst (TWC) with multi-point fuel injection (MPFI), oxidation catalyst and non-catalyst-equipped). Overall, driving cycle had the most significant effect on particulate emissions, with all vehicle technologies showing a statistically significant increase in particulate emissions on the UC over the FTP. This effect was largest on an absolute and relative basis for the oxidation and non-catalyst vehicles. The effect of fuel composition on particulate emissions was smaller than the effect of driving cycle and varied between vehicle technologies. The fuel effect was largest for the non-catalyst vehicle, with RFG producing lower particulate emissions than the pre-1992 fuel.

The scope of testing was broadened for Phase 2 to expand the database of particulate emissions over the UC for a larger and more representative fleet. The test matrix included vehicles in the following categories: 1955-1974 (1), 1975-1980 (4), 1981-1985 (7) and 1986+ (12). Unified Cycle particulate mass emission rates from 1986 and newer gasoline vehicles were generally low ( < 5 mg/mi ) with modest increases in emission rates found for older model year and emission control technologies. Overall, the mass emission rates were comparable to those observed previously for FTP testing of larger vehicle fleets. Measurements of particulate size distributions and chemical composition were also included the test matrix for Phases 1 and 2.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

Stay involved, sign up with ARB's Research Email Listserver