EONV Test Parameter Adjustment for Variable Displacement Engine Vehicles
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Solution Overview
Problem
Variable displacement engines (VDEs) face issues with false failures in engine-off natural vacuum (EONV) tests due to overestimation of heat generation, leading to aborted or indeterminate results, as existing tests are based on heat rejection indicators suitable for engines with all cylinders active, whereas VDEs generate less heat.
Innovation Solution
Adjusting EONV test parameters based on the ratio of cylinder run time to total vehicle run time to accurately reflect heat rejection and tank pressure changes, ensuring the test is initiated only when a threshold amount of heat is generated, thereby reducing false failures and improving test robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EONV test parameters are based on heat rejection indicators for engines with all cylinders active, then the test can be initiated, but false failures occur due to overestimation of heat generation in VDEs
Solution Approach 1:
The patent changes the parameter basis for EONV test initiation from total vehicle run time to the ratio of cylinder run time to vehicle run time. This parameter transformation accounts for the actual heat-generating activity in VDEs, where not all cylinders operate continuously, thereby aligning the test parameters with actual thermal conditions and eliminating false failures
Solution Approach 2:
The system uses feedback from cylinder run time monitoring to dynamically adjust EONV test parameters. By continuously tracking the actual operation of cylinders and comparing it against total vehicle run time, the system adapts the test initiation criteria to reflect real-time thermal conditions, ensuring accurate test performance in VDE configurations
2Productivity
If EONV test is initiated with minimal cylinder activation time, then the test execution rate increases, but the test results become aborted or indeterminate
Solution Approach 1:
The patent implements dynamic test initiation criteria that adapt to the actual thermal state of the fuel system. Rather than using fixed time-based thresholds, the system dynamically evaluates the ratio of cylinder run time to vehicle run time, allowing the test to be initiated only when sufficient heat has been generated regardless of total elapsed time. This dynamic approach ensures both high execution rate and valid results by preventing premature testing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and reliability of EONV tests for VDEs, reducing warranty costs associated with poor test metrics by ensuring the test is only initiated when sufficient heat has been rejected, thus avoiding false failures and improving overall test performance.
Implementation Method 1
As a fuel tank cools down, a vacuum is generated therein as fuel vapors condense to liquid fuel
Implementation Method 2
The pressure in such a fuel system will increase if the tank is heated further (e.g. from hot exhaust or a hot parking surface) as liquid fuel vaporizes
Data Source
AI summary
A method, comprising: adjusting an evaporative emissions leak test parameter based on a ratio of cylinder run time of a deactivatable cylinder of an engine, to vehicle run time; and indicating degradation based on the adjusted parameter. The adjusted parameter may thus more accurately reflect the state of a vehicle configured to run with one or more cylinders deactivated. In this way, the evaporative emissions leak test may realize improved robustness and performance metrics, thus reducing warranty costs associated with poor test metrics.