Patent ID: 6390077
Filing Date: 2002-05-21
Classification: F02D,F02M

Abstract:
A method for flow restriction testing an engine EGR system including an EGR valve and associated tubing for directing a flow of engine exhaust gas into an engine intake manifold, the method including the steps of increasing an opening of the EGR valve to a test opening, measuring a pressure change in the intake manifold from an initial pressure due to the increased opening of the EGR valve, and indicating a passing EGR system if the measured pressure change exceeds a threshold based on a minimum expected change in intake manifold pressure for an EGR system functioning within acceptable limits, the improvement wherein:the test opening is initialized at a determined value that minimizes degradation of engine operation for an EGR system with substantially unrestricted flow of engine exhaust gas; if the measured pressure change due to the test opening is less than said threshold, periodically increasing the test opening and re-measuring the pressure change due to the increased test opening; if the re-measured pressure change exceeds the threshold, indicating a passing EGR system and recording the test opening in effect when the re-measured pressure change exceeds the threshold; if the test opening is increased to a maximum opening without the re-measured pressure change exceeding the threshold, indicating a failing EGR system; and at a subsequent time during operation of the engine, repeating said flow restriction testing with said test opening initialized to a new value based on said recorded test opening.