EVAP Diagnostic Test Completion During Engine Stop-Start Cycles
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Solution Overview
Problem
Automatic engine stop-start operations in vehicles interfere with the completion of evaporative emissions system diagnostic tests, as the vacuum pressure needed for testing is lost when the engine stops, making it difficult to perform required diagnostic testing.
Innovation Solution
A method that determines if an engine stop is allowed during a diagnostic test and prevents the engine from stopping if the test is not complete, using software to prioritize test execution and calibration thresholds to manage engine stops and restarts, ensuring diagnostic tests are completed before allowing engine stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is configured to automatically stop and restart to increase fuel economy, then fuel economy is improved, but the ability to perform EVAP diagnostic testing deteriorates
Solution Approach 1:
The system performs preliminary assessment of EVAP diagnostic test status before allowing engine stop. The controller checks whether a diagnostic test is currently being performed or can be completed, and only allows engine stop if the test is not in progress. This preliminary check prevents the engine stop from interfering with diagnostic testing while still enabling fuel economy benefits when appropriate.
2Use of energy by moving object
If the engine stops during EVAP diagnostic testing to maximize fuel economy, then fuel economy is improved, but the completion of diagnostic testing deteriorates
Solution Approach 1:
The controller continuously monitors the status of EVAP diagnostic tests and uses this feedback to make real-time decisions about allowing engine stop. When a diagnostic test is detected as being in progress, the controller provides feedback to prevent engine stop. This feedback mechanism ensures diagnostic tests are completed without interruption while still permitting engine stop during normal operation to maximize fuel economy.
Data Source
AI summary
A method of operating an engine in a vehicle equipped with an evaporative emissions system is described. The engine is configured to perform automatically an engine stop and an engine restart when the vehicle stops moving to increase fuel economy of the vehicle. The method includes the steps of determining if an engine stop is allowed while a diagnostic test of the of the evaporative emissions system is being performed if an engine stop is requested, and preventing the engine stop if the engine stop is not allowed.