O2 queston

[tbaum12]

New to programming and i have noticed some of you talk about monitering the exhast with a tool hooked to the scanner. just wondering what tool it is how it works, and what you are checking for?

[Ryan]

New to programming and i have noticed some of you talk about monitering the exhast with a tool hooked to the scanner. just wondering what tool it is how it works, and what you are checking for?

Hi tbaum, welcome to the forum. :cheers:

What people are likely referring to are wideband O2 sensors (although sometimes people utilize exhaust gas temperature sensors, too). The sensor is "hooked" to the scan tool either directly through the analog inputs on the Flashscan unit, or through the stock narrowband harness.

The wideband O2 sensor is designed to determine the percentage of oxygen in the combustion by-products. Air is approximately 20.9% oxygen, which is used to reference the amount of oxygen in the exhaust, giving us an air-fuel ratio (AFR). The stoichiometric ratio for gasoline combustion is 14.7 parts of air to fuel, but sometimes, we use different ratios as necessary. I suggest you refer to this page: http://forum.efilive.com/showthread.php?t=6328

How the device technically works is probably more information than you really wanted to know, but you can read more here: http://auto.howstuffworks.com/question257.htm

Simplistically, the purpose of the computer is to measure the incoming airflow and provide the correct amount of fuel, along with controlling the spark timing. Using the wideband O2 sensor, we can determine the difference between the commanded AFR by the PCM and the reported AFR we measure in the exhaust. The idea of tuning the computer is to make these two values equal.

[odd boy]

first welcome to the forum :welcome:

What Ryan said is right, below some info about wideband and the narrow one.

Narrow band (attached to the car's headers) setups are great for allowing the stock ECU to keep itself in a happy state of tune for emmissions and stock power. The only problem is they are only accurate in a very narrow range of A/F ratios (thus they are called narrowbands). A wideband o2 sensor will give a linear output for the entire range of A/F ratios that you can possibly see coming out of the engine.

The narrow band sensors was designed to achieve a stoichiometric (14.7:1) mixture under closed loop conditions, as this is the point where optimum catalytic converter efficiency is achieved. There are ways to guess your actual air/fuel ratio (AFR), but there is only one tool which can give you exact values. That tool is the wide band oxygen sensor. The wide-band sensor expands on the principle of the two-state sensor narrow band function by incorporating a second chamber, the pump cell. The Wide Band Sensors are used in the pre catalyst position in the exhaust stream. They look similar to the Oxygen sensors that you have been accustomed to, however there are some differences.

The sensors for wide band systems are very similar to the ones that you are used to. They look a lot alike with a few exceptions. The sensors will have 6 wires connected to them (Heater power and ground, Reference high and low, and 2 wires for pumping current. The ECM is attempting to maintain a constant 450 mV potential difference between the reference voltage and low reference circuits by increasing or decreasing the abundance of oxygen ions in the exhaust gas sample chamber, an external electrical force is required to move the oxygen ions. That's where the 2 extra wires for the pump current comes in. The ECM relies on Pumping Current to move electrons, here's how;

The ECM supplies a pumping voltage to the ion conductive material that separates the exhaust gas sample chamber and the exhaust stream. As the pumping voltage, and thus the pumping current, increases or decreases, as well as changes polarity, oxygen ions will be moved from the exhaust stream through the ion conductive material into the exhaust gas sample chamber. Ions may also be moved from the exhaust gas sample chamber through the ion conductive material back into the exhaust stream. The ECM monitors the pumping voltage level and polarity required to maintain the 450 mV potential difference between the reference voltage circuit and the low reference circuit electrodes and uses this information to change the air/fuel ratio accordingly. This new commanded air/fuel ratio will burn in the engine cylinders, then pass the sensor, entering the exhaust gas sample chamber, and the adjustment process will start again. This process happens extremely quickly and thus makes the wide-range sensor much more accurate, fast, and able to detect greater deviations, rich or lean, from the stoichiometric air/fuel ratio.

[tbaum12]

Thanks for the help Ryan and Odd Boy. The obove info helped alot, but only raises one more question. How do I hook it up to the scan tool to see what the what the ratio is in the exhuast, and do I need any special tools?

[Ryan]

Thanks for the help Ryan and Odd Boy. The obove info helped alot, but only raises one more question. How do I hook it up to the scan tool to see what the what the ratio is in the exhuast, and do I need any special tools?

The only tools you need are that which allow you to put the O2 into the bung in the exhaust (typically immediately following the manifold flange or in the collector of the header). You can buy an O2 socket from any parts store, or you can use whatever you have handy to get it out. Using a dab of anti-seize on the threads of the O2 sensor is a good idea.

There are two ways of logging the values reported by the wideband in the scanner: one is through direct connection from one of the wideband's analog outputs into the Flashscan device through the analog inputs. The other is through the stock narrowband harness, and setting up a custom PID for wideband AFR from the narrowband O2 voltage PID.

I used the latter approach because it was easier to move between cars, but most use the former. Wiring depends on the unit used, but I think they are pretty similar between the various makes.

What wideband are you attempting to wire, or which are you considering purchasing?

[odd boy]

I have LM-1, u can connect it to V2 and it has its own LCD too.

[tbaum12]

sorry took so long to reply. have been real busy at work. Have not picked which wideband i am going to use yet.

[odd boy]

There is a lot of brands in the market, below are the compatible types with EFILive:

1. Autronic
2. Innovate LC-1
3. Innovate LM-1
4. PLX
5. Tech Edge
6. Wide Band Commander