- Sat Nov 29, 2008 4:31 pm
#80850
What all is the purpose of an o2 sensor?
For more on it http://en.wikipedia.org/wiki/Oxygen_sensor
- Sat Nov 29, 2008 4:41 pm
#80853
"Automotive oxygen sensors, colloquially known as O2 sensors, make modern electronic fuel injection and emission control possible. They determine if the air fuel ratio exiting a gas-combustion engine is rich (with unburnt fuel vapor) or lean (with excess oxygen). Closed-loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data rather than operating with a predetermined (open-loop) fuel map. In addition to improving overall engine operation, they reduce the amounts of both unburnt fuel and oxides of nitrogen from entering the atmosphere. Unburnt fuel is pollution in the form of air-borne hydrocarbons, while oxides of nitrogen (NOx gases) are a result of excess air in the fuel mixture and cause smog and acid rain. Volvo was the first automobile manufacturer to employ this technology in the late 70s, along with the 3-way catalyst."
For more on it http://en.wikipedia.org/wiki/Oxygen_sensor
For more on it http://en.wikipedia.org/wiki/Oxygen_sensor
- Sun Nov 30, 2008 9:45 pm
#81156
The O2 sensor is a feedback device that continually checks on the air/fuel ratio so the ECU can make small corrections to keep it within an acceptable range.
In a perfect world, the factory tune would keep you at the ideal fuel ratio under all circumstances and for the lifetime of the vehicle. No O2 sensor would be needed. Unfortunately over time the engine builds up with grease, carbon, and other deposits, the piston rings don't seal perfectly, the sensors wander a bit outside of their original specification, and the owner doesn't keep to the maintenance schedule. So the ECU needs feedback to keep your car running as close to ideal as possible.
There are several conditions under which the ECU ignores the O2 sensor and runs entirely off of it's predefined fuel injection time tables. 1) wide open throttle; normal O2 sensors aren't accurate at rich air/fuel ratios and Honda wants you running rich so the engine doesn't blow up 2) when the ECU can tell that the O2 sensor is bad because it's giving weird readings, and 3) when you let completely off the throttle above 1000 RPMs the ECU cuts fuel completely.
When your O2 sensor is bad or missing, the ECU goes into limp mode running overly rich with retarded timing to keep the engine safe until you can get it home or to the repair shop. But if you run on it like this for too long you'll damage the engine (bore wash), crack the exhaust manifold, and burn out the cat converter which in turn will destroy your muffler. Not to mention very poor mpg and power output.
In a perfect world, the factory tune would keep you at the ideal fuel ratio under all circumstances and for the lifetime of the vehicle. No O2 sensor would be needed. Unfortunately over time the engine builds up with grease, carbon, and other deposits, the piston rings don't seal perfectly, the sensors wander a bit outside of their original specification, and the owner doesn't keep to the maintenance schedule. So the ECU needs feedback to keep your car running as close to ideal as possible.
There are several conditions under which the ECU ignores the O2 sensor and runs entirely off of it's predefined fuel injection time tables. 1) wide open throttle; normal O2 sensors aren't accurate at rich air/fuel ratios and Honda wants you running rich so the engine doesn't blow up 2) when the ECU can tell that the O2 sensor is bad because it's giving weird readings, and 3) when you let completely off the throttle above 1000 RPMs the ECU cuts fuel completely.
When your O2 sensor is bad or missing, the ECU goes into limp mode running overly rich with retarded timing to keep the engine safe until you can get it home or to the repair shop. But if you run on it like this for too long you'll damage the engine (bore wash), crack the exhaust manifold, and burn out the cat converter which in turn will destroy your muffler. Not to mention very poor mpg and power output.