The major sources of variability of an exhaust emission test on the 1975 Federal Test Procedure (FTP) are discussed. Vehicle, driver and the ambient conditions affect hydrocarbon (HC) and carbon monoxide (CO) variability significantly. On the other hand, oxides of nitrogen (NO sub x) and carbon dioxide (CO sub 2) are infleunced more by the differences in vehicle loading. Various diagnostic aids which are used for the purpose of a better correlation between measurement systems on different test sites, are described. A computer simulation of emissions was also employed to determine relative contributions from different sources to overall variability. Variability due to measurement error and within--vehicle variability observed in this work is +19% of the mean for HC, plus minus 33% of the mean for CO, plus minus 9% of the mean for NO sub s and plus minus 5% for the mean for CO sub 2. The magnitude of variability is variable depending on differences in the overall system which includes the vehicle, the measurement system and test operating conditions. /GMRL/

  • Corporate Authors:

    Society of Automotive Engineers (SAE)

    400 Commonwealth Drive
    Warrendale, PA  United States  15096
  • Authors:
    • Juneja, W K
    • Horchler, D D
    • Haskew, H M
  • Publication Date: 1977-3

Media Info

  • Pagination: 24 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00165015
  • Record Type: Publication
  • Report/Paper Numbers: SAE 770136
  • Files: TRIS
  • Created Date: Nov 23 1977 12:00AM