A Study of a Fast Light-Off Planar Oxygen Sensor Application for Exhaust Emissions Reduction

It is well known that hydrocarbon reduction during a cold start is a major issue in achieving ultra low emissions standards. This paper describes one of the possible approaches for reducing the cold-start hydrocarbon emissions by using a fast “light-off” planar oxygen sensor. The goal of this study was to verify the operation characteristics of Delphi's fast “light-off” planar oxygen sensor's (INTELLEK OSP) operating characteristics and the closed-loop performance for achieving improved hydrocarbon control for stringent emission standards. Tests were conducted in open-loop and closed-loop mode under steady and transient conditions using a 1996 model year 2.4-liter DOHC in-line 4-cylinder engine with a close-coupled catalytic converter. Overall performance of the OSP showed relatively quick reaction time to reach the operating temperature. During the first 30 second cold-start period of the FTP 75 cycle, the closed-loop control and A/F ratio were adjusted as lean as possible up to the stoichiometric A/F ratio without impacting drive-ability. Engine out hydrocarbon emissions, for the first cold cycle, were reduced by 8.1% using the OSP and a shorter open-loop time. The operating characteristics of the OSP during a cold-start made it possible to achieve closed-loop control in less than ten seconds. Early closed-loop control can contribute directly to reducing hydrocarbon emissions.