What is a Broadband Oxygen Sensor? General information about the air/fuel ratio sensor and AFR sensor. Wideband oxygen sensor
What is Wideband Oxygen Sensing?
The oxygen sensors that monitor the mixture of air and fuel are evolving with engine management and diagnostics systems. Broadband oxygen sensors are smarter, faster, more durable and capable of measuring air/fuel ratios precisely – an achievement that was impossible with previous generation O2 sensors.
You may be familiar with oxygen sensors, which are used to measure the amount of unburned oxygen in exhaust. The oxygen in the exhaust after combustion is an indicator of the fuel mixture’s relative richness and leanness. For ideal combustion to take place in the cylinders, and for full combustion of all fuel, a certain amount of air must be present. It is approximately 14.7 kg of air to 1 kg of gasoline. This is known as the stoichiometric “air/fuel ratio” . It can also be referred to as “lambda ( λ)” Greek When lambda is equal to one (λ = 1), you have a stoichiometric air/fuel ratio of 14.7:1 and ideal combustion. The air/fuel ratio greater than 14.7 to1 will result in lambda being greater than 1, and the engine will burn more fuel.
A lean mixture can reduce fuel consumption, but it will cause an increase in nitrogen oxides. The mixture may not ignite if it is too thin. “misfire” This can lead to a significant increase in unburned hydrocarbons (HC) emissions. This can lead to erratic idling and hard starting, stalling, and even the destruction of the catalytic converter. This increases the chance of the engine misfiring timing or knocking under load.
When the air/fuel ratio is less than 14.7:1, the lambda is less than one (λ = 0.9) and the engine has a rich fuel mixture. When starting a cold engine, or when the engine is running under load, a rich fuel mixture is necessary. However, rich mixtures result in a sharp rise in carbon monoxide(CO) emissions.
The relative ratios of fuel and air can be determined “just right” This mixture produces little emissions and burns clear. It is important to balance the mixture as driving conditions, temperatures, loads and loads change constantly. These are where oxygen sensors come in.
The sensor(s), which monitor the level unburned oxygen at the exhaust, tells the engine computer (PCM/ECM / CU) when fuel mixture is rich or lean. The computer adjusts fuel mixture to compensate for this by adding fuel more often when the mixture is rich or reducing fuel usage when it’s lean. This is the basic feedback fuel control loop.
Unfortunately, narrow-band O2 sensors cannot accurately report the ratio of fuel to air because they only produce two types (high and low) of voltage signals. A narrowband O2 sensor will produce a signal of 0.45 volts (450 microvolts) when the fuel/air ratio is perfect. The O2 sensor output voltage quickly reaches its maximum output when the fuel mixture becomes slightly more dense.
When the fuel mixture is not rich, however, the output voltage of the sensor drops to 0.1 V. The engine computer adjusts the amount of fuel delivered to the engine computer if the output voltage of the oxygen sensor changes. This rapid reciprocating motion allows feedback fuel control to maintain an average amount of fuel. This tried-and true approach has not been able to meet the most recent emissions standards.
This is how we can explain it:
The ECU will reduce injector time to bring fuel mixture to 14.7 percent if it detects an air/fuel ratio greater than 14.5:1. If the ECU detects that the fuel/air ratio is 15.0:1, it will prolong the injector time for enriching the fuel/air mixture. This works great on a stock motor with no modifications, but the ideal air/fuel ratio (usually 12.0 to about 13.5%) is required for maximum performance. This air/fuel ratio cannot be distinguished by the narrowband O2 sensor and can’t tell the ECU how much fuel it should add or subtract.
The new emission standards require exact controls of the air/fuel ratio. These standards require that cold emissions be reduced as soon as the engine is turned on. However, conventional oxygen sensors (even those with heaters), heat up too late in order to achieve the level of accuracy required to meet cold emission standards. As advanced fuel control strategies evolve, they are unable to report exact air/fuel ratios to the PCM. A simple warning about rich-poor mixture is no longer sufficient in today’s world.
The most recent generation of oxygen sensors is now available Broadband is also known as Lambda sensors “air/fuel ratio sensors” They do exactly that. They give an accurate indication of the fuel/air ratio. They can measure fast and accurately in the pure air range with Lambda = 0.0.7 (11 to1 fuel/air ratio).
The reference voltage is received by the broadband oxygen sensor and the signal current generated by the fuel mixture. The sensor does not produce an output voltage if the mixture of fuel and air is balanced at 14.7 to 1. The sensor will produce a negative current if the mixture of fuel and air is too rich. This is when the lambda value is 0.7 is high and the ratio between fuel/air is close to 11.
The sensor will produce a “positive” current when the mixture is almost dry. It goes from zero up to 1.5 milliamps for mixtures that are nearly air. The broadband oxygen sensor responds in less than 100 milliseconds for changes in the mixture. It also uses its internal heater to heat up to 700 to 800 degrees Celsius (1340 degrees F) in just 20 seconds. This is more than twice the operating temperatures of an ordinary oxygen sensor.
Many engine builders have realized the advantages of broadband oxygen sensor technology for monitoring air/fuel ratios. This allows fuel mixtures to be adjusted and fine-tuned on the spot. This is possible with expensive equipment, but it was not possible before.
In turbocharged, supercharged high-performance engines, the air/fuel ratio is crucial to power the engine and to fuel it at high revs. The engine will eventually self-destruct if the mixture setting is not maintained.
Here are some things to keep in mind when you purchase a wideband sensor.
There are some qualities you should look out for when using a broadband O2 sensor in order to tune an engine and read fuel/air ratios.
