A three-way catalyst with feedback control monitors the exhaust oxygen concentration and controls the fuel flow to produce a stoichiometric exhaust mixture. The control loop consists of zirconium dioxide exhaust sensor to indicate oxygen concentration, an electronic control unit, a vacuum regulator to proportion a vacuum signal to the carburetor, and a feedback controlled carburetor with vacuum modulated main fuel system. Not only does the system pass the 50K emission and durability testing, but it has excellent deterioration factors. Fuel economy was improved as compared with other conventional California emission systems: 14% metro-highway advantage for automatic transmission applications and 7% advantage for manual transmission applications. Driveability is improved because exhaust gas recirculation rates are significantly reduced, more than offsetting the leaner air/fuel ratio. Wide open throttle performance is equal to that of conventional systems; idle quality is not depreciated. Major developmental issues are idle system control, feedback carburetor diaphragm development, exhaust gas oxygen sensor, ramp rate, and control hydrocarbons emissions.

  • Supplemental Notes:
    • Presented at the SAE Congress and Exposition Detroit, 27 February-3 March 1978.
  • Corporate Authors:

    Society of Automotive Engineers (SAE)

    400 Commonwealth Drive
    Warrendale, PA  United States  15096
  • Authors:
    • Seiter, R E
    • CLARK, R J
  • Publication Date: 1978

Media Info

  • Features: References;
  • Pagination: 18 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00395636
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: SAE 780203, HS-025 346U
  • Files: HSL, USDOT
  • Created Date: Jun 30 1985 12:00AM