Wideband Questions

[Doug]

I'm just about to finish my wiring on my sr20det blacktop and i have a few questions about the wideband o2 setup. Do i still need my regular o2 sensor if i have an AFC NEO? Is there a way to wire the wideband so that the ecu gets a reading from it, thus only using one o2 sensor?

[silverarrow27]

You don't have to use your stock o2 sensor at all really, it's only there for gas mileage/emissions purposes.  I haven't heard of a way to wire in a wideband into the stock ecu; I'm not sure what your goal is, but most widebands do usually come with one or you're able to purchase one with an a/f ratio gauge for tuning purposes.

[Doug]

well my only goal is to get my car running, however i made the mistake of selling the sr20det t25 mani and turbo with the o2 still attached. I have a UEGO for tuning and an AFC NEO but i thought the ecu would need the stock o2 for proper driveability, im not sure to what extent the ecu uses the o2 reading to dictate the a/f ratios.

[silvia love]

copied and pasted from wiki

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.

Information on oxygen concentration is sent to the engine management computer or ECU, which adjusts the mixture to give the engine the best possible fuel economy and lowest possible exhaust emissions. Failure of these sensors, either through normal aging, the use of leaded fuels, or fuel contamination with silicones or silicates, for example, can lead to damage of an automobile's catalytic converter and expensive repairs.

Tampering with or modifying the signal that the oxygen sensor sends to the engine computer can be detrimental to emissions control and can even damage the engine. When the engine is under low-load conditions (such as when accelerating very gently, or maintaining a constant speed), it is operating in 'closed-loop mode'. This refers to a feedback loop between the fuel injectors and the oxygen sensor, to maintain stoichiometric ratio. If modifications cause the mixture to run lean, there will be a slight increase in fuel economy, but a great increase in nitrogen oxide emissions, and the risk of damaging the engine due to detonation and excessively high exhaust gas temperatures. If modifications cause the mixture to run rich, then there will be a slight increase in power, again at the risk of overheating and igniting the catalytic converter, while decreasing fuel economy and increasing hydrocarbon emissions.

When an internal combustion engine is under high load (such as when using wide-open throttle), the output of the oxygen sensor is ignored, and the engine automatically enriches the mixture to protect the engine. Any changes in the sensor output will be ignored in this state, as are changes from the air flow meter, which might otherwise lower engine performance due to the mixture being too rich or too lean, and increase the risk of engine damage due to detonation if the mixture is too lean.

[Doug]

so its basically only using the oxygen sensor when the motor is not being floored. Would any oxygen sensor signal work to send the motor the information it needs? as in could i use my ca18et o2 sensor on my sr20det? should all be the same 0-1v signal i would assume. I know the ca18et is a "fat-type" o2 sensor and will fit in the bung on my down pipe, allowing me to relocate my wideband further down the exhaust stream where its more useful. Any ideas on this?

[bartc_j]

well almost all the older cars only use the the o2 sensor to stoch mixture when crusiing when floored the ecu only uese the afm/air temp signals as inputs for predetermined fuel curves under hard acceleration.... not the other way around as some may think. as far as locating ur o2 farther down thats also backwards you want the wideband as close as possible to the turbo as possible the farther away u get the cooler the temps and less accurate readings.. i now it may seem that a few inches dont really matter but they actually make a huge difference in how accurate the readings will be

[gearhead313]

I'm just about to finish my wiring on my sr20det blacktop and i have a few questions about the wideband o2 setup. Do i still need my regular o2 sensor if i have an AFC NEO?

YES

Is there a way to wire the wideband so that the ecu gets a reading from it, thus only using one o2 sensor?

NO

a wide band uses a much higher resolution than a stock narrow band.  Some common cases are a stock o2 using a 0-1v signal and a wideband using a 0-5v signal.

[silverarrow27]

Any wideband system would recommend to have the wideband o2 mounted at least 12 inches away from exit I believe.

[bartc_j]

Any wideband system would recommend to have the wideband o2 mounted at least 12 inches away from exit I believe.

exactly but the truest readings will be had at about 2-3 inches from the exhasut ports, but such a setup is only on race cars that meter each cylinder individually

[Doug]

ok, is the ca18et o2 sensor able to send the correct signal to the sr20det ecu? i cant think of a reason it wouldnt be able to but maybe theres something i missed.

[silvia love]

isnt the 18et a one wire o2 sensor? sr is 3 wire, right?

[Doug]

my ca18et has a 3 wire fat type o2 sensor in it, which is why i asked because i know the skinny and fat type are different.

[bartc_j]

fat or skinny type i believe all o2's uae the same thread size

[nismo200sx16]

fat and skinny are the same signal. differences are if its heated or not. you should just go on ebay and get a universal o2 sensor that matches your motor. which would be the 3 wire o2 sensor. the universal ones are way cheaper cause they don't have the plug that plugs in to your car. so you just crimp the wires  together with but connectors or sodder them. I have used the ebay ones and they work just as well as the ones you get from the auto parts store but for a third of the price. and yes you can run your car with some wide band's. my sr in my s12 runs with the narrow band out put from my plx m500. and I also made a box with resisters to make the ecu think its still heating the o2 sensor. so I get no cel. so your best bet would be to get a new o2 off ebay and wire it up. unless your wide band has a narrow band output.