Speed Density Engine Control Using Manifold Pressure
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Solution Overview
Problem
Existing fuel injection systems relying on air flow meters (AFMs) are affected by pulsations in the intake system, leading to inaccurate air mass measurement and reduced engine performance, especially after engine modifications that alter the airflow patterns.
Innovation Solution
Implementing a speed density method that uses volumetric efficiency based on engine speed and manifold pressure, measured by a manifold absolute pressure (MAP) sensor, which is less affected by pulsations and provides more accurate fuel injection determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an air flow meter is used to measure air mass flow, then the fuel injection system can achieve precise air-fuel ratio control under normal conditions, but the measurement accuracy deteriorates when intake system pulsations increase due to engine modifications
Solution Approach 1:
The patent changes the measurement parameters from direct air flow measurement (velocity-based) to pressure-based measurement. By measuring manifold absolute pressure and using the speed density method with volumetric efficiency tables, the system transforms the measurement approach to one that is less sensitive to flow pulsations, thereby maintaining accuracy across different engine configurations
Solution Approach 2:
The patent introduces manifold absolute pressure as an intermediary measurement parameter. Instead of directly measuring air flow velocity which is disrupted by pulsations, the system measures pressure (a more stable parameter) and derives air mass information through calculations involving volumetric efficiency, engine speed, and pressure data
2Measurement precision
If an air flow meter is installed in the intake system, then air flow measurement is possible, but the system becomes sensitive to pulsations and non-linear flow patterns caused by engine modifications
Solution Approach 1:
The patent extracts the measurement function from the direct air flow path by removing the air flow meter from the intake system. Instead of placing a sensor in the pulsating air stream, the system uses a manifold absolute pressure sensor that measures pressure in a location less affected by flow pulsations, thereby eliminating the harmful sensitivity to pulsations while retaining measurement capability
Solution Approach 2:
The patent replaces the mechanical air flow measurement system (air flow meter with moving parts or hot wire elements) with a pressure-based measurement system. This substitution uses a manifold absolute pressure sensor that is less susceptible to mechanical disturbances from pulsations, and employs computational methods (speed density calculation) to derive air mass information
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 results in more accurate fuel injection and improved engine performance by reducing the impact of airflow pulsations and allowing for better tuning of the air-fuel ratio, even with altered engine intake systems.
Implementation Method 1
The manifold pressure is then measured by a manifold absolution pressure (MAP) sensor
Data Source
AI summary
The present invention utilizes a speed density method for determining the cylinder air mass using volumetric efficiency (VE) based on engine speed and manifold pressure. The VE data contain the cylinder filling efficiency for various engine speed and manifold pressure values. The manifold pressure is then measured by a manifold absolution pressure (MAP) sensor. Using the speed density has the advantage that it is much less affected by pulsation in the intake system of the vehicle, and does not require a linear air flow past a sensor in the engine intake system.