Important Role of Fuel Trim for Ideal Air-Fuel Ratio
Important Role of Fuel Trim for Ideal Air-Fuel Ratio
This is a fuel trim chart. The chart shows how much fuel is added to a car’s exhaust system to maintain the ideal air-fuel ratio for optimal performance and emissions.
- Rich Exhaust: The left side of the chart indicates a rich exhaust condition. This means there is too much fuel and not enough air in the mixture.
- Lean Exhaust: The right side of the chart indicates a lean exhaust condition. This means there is too much air and not enough fuel in the mixture.
The ideal air-fuel ratio is typically around 14.7:1. This means that for every 14.7 parts air, there is 1 part fuel. The fuel trim system adjusts the amount of fuel injected into the engine based on the signal received from the oxygen sensor in the exhaust. The oxygen sensor measures the amount of unburned oxygen in the exhaust. If the exhaust is rich, the oxygen sensor will send a signal to the engine computer to reduce the amount of fuel injected. If the exhaust is lean, the oxygen sensor will send a signal to the engine computer to increase the amount of fuel injected.
The fuel trim chart in the image is labeled with percentages. The percentages indicate how much the fuel injection is being adjusted. A positive percentage means that the fuel injection is being increased. A negative percentage means that the fuel injection is being decreased.
- Go Lean Command: This text appears at the top left of the chart and corresponds with a negative percentage. It means that the engine computer is reducing the amount of fuel injected because the exhaust is rich.
- Go Rich Command: This text appears at the top right of the chart and corresponds with a positive percentage. It means that the engine computer is increasing the amount of fuel injected because the exhaust is lean.
The chart also has a vertical axis labeled “Subtracting Fuel” in the green area and “Adding Fuel” in the yellow area. The horizontal axis is labeled from -25% to +25%. At 0% on the horizontal axis, there is a horizontal line labeled “No Adjustment” which means the fuel injection is not being adjusted because the air-fuel ratio is ideal.
In conclusion, the fuel trim chart is a diagnostic tool that can be used to identify problems with the engine or the fuel injection system. If the fuel trim values are consistently positive or negative, it may indicate a need for repairs.