Vehicle Fuel Consumption Accuracy via OBDII Fuel Trim Correction
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Solution Overview
Problem
Current methods for determining fuel consumption and fuel efficiency in vehicles are not accurate and reliable, despite the presence of OBDII systems in vehicles, which collect real-time data from MAF and MAP sensors.
Innovation Solution
A system and method using OBDII-connected devices, such as the Vehicle Interface Unit (VIU), to collect and process MAF and MAP sensor data, incorporating long-term and short-term fuel trim values, to calculate fuel consumption and efficiency, with data aggregation and reporting through a central host system like OverVIU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If MAF and MAP sensor data is used to calculate fuel consumption, then real-time monitoring capability is improved, but measurement precision deteriorates due to deviations in air-to-fuel stoichiometry
Solution Approach 1:
The system retrieves long-term and short-term fuel trim values from the vehicle's ECU, which represent feedback corrections to the base fuel injection calculations. These trim values are applied to adjust the calculated fuel consumption, compensating for deviations caused by aging, environmental conditions, and other factors that affect air-to-fuel stoichiometry.
Solution Approach 2:
The system changes the parameters used in fuel consumption calculation by incorporating fuel trim values (both long-term and short-term) alongside the base MAF/MAP data. This parameter adjustment transforms the calculation from a theoretical stoichiometric-based computation to a corrected computation that reflects actual operating conditions and aging effects.
2Measurement precision
If fuel trim values are applied to correct fuel consumption calculations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system leverages the vehicle's existing ECU, which already maintains long-term and short-term fuel trim values for emissions control purposes. By retrieving and utilizing these pre-existing correction values, the system avoids the need for separate sensors or complex correction algorithms, effectively using the vehicle's own self-diagnostic data to improve measurement accuracy.
Solution Approach 2:
The fuel trim values serve dual purposes: they are used by the ECU for emissions control and by this system for accurate fuel consumption measurement. This multi-functional use of existing data reduces system complexity, as no additional components or data collection mechanisms are required beyond the OBDII interface.
3Ease of operation
If OBDII data is used for fuel consumption determination, then ease of operation is improved, but reliability deteriorates due to insufficient correction for operating conditions
Solution Approach 1:
The system performs preliminary retrieval and averaging of long-term and short-term fuel trim values before applying them to the fuel consumption calculation. This preliminary action ensures that the correction factors are ready and properly processed, improving the reliability of the final measurement while maintaining the simplicity of using existing OBDII data.
Data Source
AI summary
A method of determining fuel consumption in a vehicle through the OBDII bus is described. The fuel consumption is determined by using mass air flow (MAF) sensor data or manifold air pressure (MAP) sensor data, and obtaining and applying long term and short term fuel trim values for the vehicle, which respectively characterize deviations of air-to-fuel stoichiometry in the vehicle due to aging and vehicle's current operating conditions to determine the corrected fuel consumption in the vehicle. For MAP based method, an independent determining of Volumetric Efficiency of a vehicle's engine is also provided. The method is further enhanced by providing various sensing patterns for various sensor data, which depend on the rate of change of the respective data.