Search Results

Traditional EGR measurement systems using delta pressure over a fixed orifice such as a DPFE sensor (Delta Pressure Feedback for EGR), have limitations in the ability to measure EGR accurately. Also, the pressure drop that results from the orifice may not be acceptable in some applications. To measure the EGR accurately and without any pressure loss, a new measurement system was developed that uses an oxygen sensor in the intake air. In this paper, the technology of using an oxygen sensor to measure the EGR concentration is discussed. The paper details the EGR measurement principle with an oxygen sensor and the associated mathematical relations of translating the oxygen measurement to EGR measurement. Factors affecting the EGR measurement such as the air/fuel ratio of the EGR, intake air pressure, and diffusion effects of the EGR constituents are discussed in detail. Compensation mechanisms are explained and associated results shown.

Emission studies and component analyses were carried out on Clear-fueled and MMT®-fueled 100,000 mile Escort vehicles from the Alliance study [SAE 2002-01-2894]. Previously reported analyses of these vehicles indicated that all differences in emission system performance could be attributed, with a 90% confidence level, to the engine cylinder head, spark plugs, oxygen sensors, and catalysts [SAE 2004-01-1084]. These parts from the Clear and MMT®-fueled vehicles were further analyzed to determine the root causes of the differences in emission system performance. The intake/exhaust valves, fuel injectors, and EGR valves from the cylinder heads were tested, individually and in groups, for differences in vehicle emission performance. Deposits from the exhaust valves of the MMT®-fueled vehicle were characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDX), and shown to resemble Mn3O4 with partial substitution of Zn2+ for Mn2+.