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Air Fuel Gauges: Frequently Asked Questions
An air-fuel gauge, also known as an AFR gauge or ratio meter, monitors the air/fuel ratio of an internal combustion engine. It reads the voltage output of an oxygen sensor, which is sometimes referred to as an AFR or lambda sensor.
There are also ethanol gauges, which are designed to detect ethanol content via the sensor, which also measures fuel temperature.
What Do They Do?
The sensors of the AFR are linked to the voltage of the vehicle's computer system, which adjusts as necessary throughout a drive.
When the voltage reaches .450V, the meter will reduce the amount provided to the engine through the injectors. Some of the benefits of using an AFR include:
- Enhanced engine performance.
- Increased fuel economy.
- Reduced emissions.
- Determines the condition of the oxygen sensor.
Do I Need an AFR Gauge?
An AFR can tell you about the balance of air and fuel in the engine. It's extremely important to have this right, so that you aren't wasting petrol. It will also tell you if your engine is running correctly, if your ratio is in a safe range, and how well your car is running under all circumstances.
These are designed to measure the ratio in a vehicle's internal combustion engine, and have been developed to deliver on greater accuracy compared to the previously used 'narrow gauge'.
Professionals swear by these and say they are a must-have, encouraging other drivers to install them so they can always know what's happening with the ratio when the car is on boost. You definitely need one of these if you don't want to blow the motor due to running lean.
What is the Best Air/Fuel Ratio?
Theoretically, the ideal ratio for complete combustion is called the stoichiometric ratio. The stoichiometric mixture for a gasoline engine is the ideal ratio of air to fuel that burns all petrol with no excess air present.
For gasoline, the stoichiometric mixture is about 14.7:1. So, for every gram of fuel: 14.7 grams of air are required.
How Do I Know if My Ratio Sensor is Bad?
Generally, when your sensor begins to show issues, this is the car’s way of alerting you that an air/fuel ratio sensor may require attention. You may start to notice the following symptoms:
- Less efficiency: If there is any problem with the sensor, it can send a bad or false signal to the computer, which can throw off its calculations and cause excessive wastage.
- Rough idle: A poor or failing oxygen sensor can send an inappropriate signal to the computer, which may throw off the idle and cause it to fluctuate or drop below the correct level.
- Decrease in engine power output: If a ratio sensor has become ‘lazy’, it will send a delayed signal to the computer over time, which may result in an overall delayed response for the entire engine. As a result, you may experience a sluggish or delayed response when accelerating, as well as a noticeable loss in speed and power.