oxygen sensors introduction
What is an Oxygen Sensor/Lambda Sensor?
Oxygen Sensors, also konwn as Lamb Sensor, is an key componet in the automobile emission control system. They are widely used in modern automobiles to control the fuel and ignition systems to optimize a car's performance in the areas of emissions and fuel economy. Oxygen sensors measure oxygen in emission, it means engine combustion could be controlled by optimizing catalytic converter. Result: minimize the emission, optimize engine performance, save fuel consumption up to 15%.
Exhaust emission standards and limit values are becoming stricter and stricter. The trend in emission values clearly shows that oxygen sensors have become indispensable in the fight to reduce exhaust emissions efficiently. In China, there are more than 15 million passenger cars equipped with gasoline engine. Many newer vehicles actually have two or more oxygen sensors.
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How does an Oxygen Sensor/Lambda Sensor work?
Oxygen sensor measures oxygen in emission, and reports the voltage signal to ECU, reflecting air fuel ratio is lean or rich. ECU controls fuel injection and air charge accordingly, for the best air fuel ratio (¦Ë=1) status for engine running, which is the ideal condition for working of catalytic converter. If the mixed air is too rich (¦Ë<1), fuel injection need to be decreased; if the mixed air is too lean, the fuel injection need to be increased (¦Ë<1),
In conventional engine management system, there is only one oxygen sensor/lambda sensor which is called control oxygen sensor/lambda sensor, equipped at upstream of catalytic converter. The newer version of passenger car is also equipped with diagnostic oxygen sensor/lambda sensor, equipped at downstream of catalytic converter. The reason is : the voltage output would be deviated due to oxygen sensor/lambda sensor damaged. Diagnostic oxygen sensor/lambda sensor could check if the control oxygen sensor worked in best work condition.
Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.
 The amount of oxygen the engine can pull in depends on factors such as the altitude and the temperature of the air and engine. |
A gasoline engine burns gasoline in the presence of oxygen. It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.
The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage. The engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.
The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.
When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.
