The closed loop secondary air control three-way catalyst system (CSA system), which controls the oxygen concentration in the exhaust gas, at stoichiometry, by adjusting the secondary air amount, to obtain the best conversion efficiency of the catalyst, was developed. This system has demonstrated a 50% higher limit cycle frequency, resulting in better conversion efficiency, especially during transient operation, and better driveability compared with closed loop intake air/fuel ratio control systems. However, to meet more stringent future emission regulations and requirements of lower fuel consumption, both exhaust air/fuel ratio control and intake air/fuel ratio drift must be improved. Response and controllability of the secondary air to the exhaust have been improved by introducing an electric air control valve (EACV). An electric carburetor bleed control system has been developed, which compensates the carburetor air/fuel ratio, through the electric bleed control valve (EBCV), by detecting its drift based on the secondary air control signal. By the combination of EACV and EBCV, the emissions and the driveability of the carburetor system have been improved to the same level as the EFI system, and the fuel consumption has become better than the EFI system. This paper describes the improved points for a better conversion efficiency and lower fuel consumption in the CSA system, development of new devices and last, the emission control capabilities of the new system.

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 273-290

Subject/Index Terms

Filing Info

  • Accession Number: 00393101
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: Proceeding, HS-037 234, HS-037 235
  • Files: HSL, USDOT
  • Created Date: Mar 29 1985 12:00AM