Research Projects

Project at a Glance

Title: Light Duty Gasoline PM: Characterization of High Emitters and Valuation of Repairs for Emission Reduction

Principal Investigator / Author(s): Durbin, Thomas

Contractor: UC Riverside

Contract Number: 05-323

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels, Monitoring


PM emissions from light duty gasoline vehicles (LDGV) could contribute an increasingly larger portion on-road PM emissions, as aftertreatment systems for diesel engines become more commonplace. The most important fraction of the LDGV fleet for PM emissions is the worn or malfunctioning vehicles that can have PM emissions orders of magnitude higher than normal, well-maintained vehicles. While the Smog Check program in California implemented a check for visible smoke starting in January of 2008, it still does not include a direct measurement of PM.

For this project, a small fleet of high PM emitters was tested for emissions at California Air Resources Boardís Haagen-Smit Laboratory (HSL). The goal of this work is to provide a better characterization of the fleet of visibly smoking and high PM emitting LDGVs, to evaluate the potential of lower cost, PM measurements for broader in-use testing, and to evaluate the potential emission reduction benefit and cost-effectiveness of professional repairs for high PM emitters. The PM instruments evaluated included an MPM4 from Maschinenbau Haldenwang (MAHA), an ETaPS from Dekati, a Dustrak and an EEPS from TSI. This project is a cooperative effort between the Air Resources Board (ARB), the University of California Riverside (UCR), the Foundation for California Community Colleges (FCCC), and the South Coast Air Quality Management District (SCAQMD) to determine the characteristics and emissions of high PM emitters, and potential emission reduction benefit and cost-effectiveness of professional repairs for high PM emitters.

The test vehicles had PM emission rates that from varied from 2.7 mg/mile to 91 mg/mile. Of the 3 vehicles repaired, one had reductions of approximately 90%, while the other two only had minor reductions. The DustTrak, the EEPS, and the MAHA were able to distinguish the three high emitting vehicles from the remaining low emitting vehicles. The DustTrak and the EEPS on average both read lower than the PM filter mass data. The MAHA required a calibration factor since the data was only available in concentration units. A linear regression between the DustTrak and EEPS and the PM mass showed a decent agreement with R2 of 0.791 and 0.943, respectively, and negative intercepts of -1.384 and -2.797, respectively, due to the lower readings of these instruments compared to the filter mass at low levels. A linear regression between the MaHa and the PM mass showed a decent agreement with an R2 of 0.852. It is also worth noting that only the MAHA is typically used for emissions measurements in the raw exhaust, which is an important consideration with respect to implementation into the smog check program. Four vehicles were repaired for a variety of issues that generally included both an engine related issue (distributor, valves, fuel injectors, spark plugs, etc.) coupled with the replacement of the catalyst or O2 sensors. The repair costs were comparable to the cost of the vehicle itself, ranging from $1,297 to $2,393, and were effective for only one of the three vehicles characterized.


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

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