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Project Status: complete

Report Published August 1987:

Title: Survey of heavy-duty diesel engine rebuilding, reconditioning and remanufacturing practices

Contractor: Sierra Research, Inc.

Contract Number: A4-152-32

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


A survey was conducted to determine the emissions impact of rebuilt, reconditioned and remanufactured heavy duty diesel engines sold in California. Proper rebuilding practices generally return engines to as new condition, that is they will emit at levels close to those of new engines. Therefore, information was collected from fleet maintenance shops, independent rebuild shops and diesel injection repair specialists on the frequency of improper rebuilding practices observed in the field. Data was also collected from manufacturers and regulatory agencies on the emissions impact of improper rebuilding practices.

An analysis of the data collected indicates that improper rebuilding practices can have a significant impact on emission levels: 25 percent for hydrocarbons (HC) and 3.1 percent for oxides of nitrogen (NOx). Stated another way, improper rebuilding practices can increase heavy duty diesl emission of HC by 11.86 tons per day and NOx BY 11.42 tons per day in 1986. These increases represent an overall increase in total vehicular emissions of 0.9 percent for HC and 0.7 percent for NOx.

Two general categories of improper rebuilding practices were identified: improper equipment replacement; and improper equipment calibration. Improper or incorrect equipment replacement is most likely to occur during a rebuild and is etimated to account for approximately 20 percent of the increase in HC emissions and 33 percent of the increase in NOx emissions identified above. Improper equipment calibration can occur either in the course of a rebuild or during normal maintenance activities in the field. It is not possible to quantitatively allocate the observed rate of improper calibration between normal maintenance and rebuild from the data collected in the survey. However, conversations with fleet and dealer rebuild shops and equipment repair facilities indicate that warranty concerns make improper calibrations financially unattractive. Therefore, it is estimated that roughly 80 percent of the 11.86 tons per day increase in HC is not due to rebuilding, but due to improper field maintenance practices. Similarly it is estimated that roughly 67 percent of the 11.42 tons per day increase in NOx is due to improper field repair practices.

The primary conclusion of the study is that improper rebuilding practices are not estimated to have a significant impact on emissions.


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

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