o 2 sensor question

[I am Technoman]

My 98 240sx has two o2 sensors. I use an Hotshot header. The front o2 sensor has stooped working and my car runs fat. I dont use my rear o2 sensor. can I use the rear o2 sensor in place of the front o2, with the front o2 harness? Or are these two sensors different or the same ?

[I am Technoman]

Both o2 sensors go from 1 v for rich and 0 v for lean. I cant see any reason why I cant use the rear in place of the front.

[drjohn]

The frt. o2 sensor is made of ceramic zirconia and this material generates a voltage between 0-1 volt. 0 being lean and 1 being rich. The rear o2 is made of ceramic titania and uses a 0-2 volt range and uses resistance to measure o2 output of rear cat. Don't know if they will work but I kind of doubt it do to one creates a volt and one measures the resistance of a applied voltage.

[I am Technoman]

The front o2 sensor detects the amount of oxygen in the exhaust gas compared to the out side air. The front heated o2 has a closed end tube made of ceramic zirconia..The zirconia generates voltage from approximately 1 V rich condition to 0 V lean condition.The ECM adjusts injector pulse to achieve the perfect air/fuel ratio.

Rear o2 sensor.The rear o2 sensor after the three way cat, monitors the level of oxygen in the exhaust gas. Even if the switching characteristics of the front o2 sensor are shifted, the air fuel is controlled to stoichiometric, by the signal from the rear o 2 sensor. This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1 V rich condition to 0 V lean conditions.Under normal conditions the rear o2 sensor is not used for engine control operation

[I am Technoman]

This is what I got from the book. But I waned to ask a pro.There both made of the same alloy and make voltage in the same range but I dont now what "stoichiometric" means.

[drjohn]

The rear o2 doesn't generate a voltage but measures the change in the supplied voltage. It opperates in a o-2.2v range. Also in the factory man. the last 2 sentences state " The rear heated ox sensor is not directly used to control the engine system. It is used only for the on board dia. of the three way cat." Put hey I could be wrong . You could just try it and see what happens!!

[Q45tech]

" but I dont now what "stoichiometric" means." and you are "I am Technoman"

Don't get offended! Just seemed dicotomistic to me.

"In chemistry, "stoichiometry" is the study of the combination of elements in chemical reactions"

"Stoichiometric or Theoretical Combustion is the ideal combustion process during which a fuel is burned completely. A complete combustion is a process which burns all the carbon (C) to (CO2), all hydrogen (H) to (H2O) and all sulfur (S) to (SO2). If there are unburned components in the exhaust gas such as C, H2, CO the combustion process is uncompleted." For most unoxygenated gasoline the point is a mass ratio of 14.6-14.7 air to fuel........stoichiometric point of combustion

The mass or volume of air required to provide sufficient oxygen to achieve this complete combustion is the "stoichiometric" mass or volume of air. Insufficient air = "rich", and excess air = "lean", and the stoichiometric mass of air is related to the carbon:hydrogen ratio of the fuel. The procedures for calculation of stoichiometric air-fuel ratios are fully documented in an SAE standard [35].

Atomic masses used are:- Hydrogen = 1.00794, Carbon = 12.011, Oxygen = 15.994, Nitrogen = 14.0067, and Sulfur = 32.066.

The composition of sea level air ( 1976 data, hence low CO2 value ) isGas Fractional Molecular Weight Relative Species Volume kg/mole MassN2 0.78084 28.0134 21.873983O2 0.209476 31.9988 6.702981Ar 0.00934 39.948 0.373114

For normal heptane C7H16 with a molecular weight = 100.204 C7H16 + 11O2 = 7CO2 + 8H2O

thus 1.000 kg of C7H16 requires 3.513 kg of O2 = 15.179 kg of air.

The chemical stoichiometric combustion of hydrocarbons with oxygen can be written as:

CxHy + (x + (y/4))O2 -> xCO2 + (y/2)H2O

Often, for simplicity, the remainder of air is assumed to be nitrogen, which can be added to the equation when exhaust compositions are required. As a general rule, maximum power is achieved at slightly rich, whereas maximum fuel economy is achieved at slightly lean.

The energy content of the gasoline is measured by burning all the fuel inside a bomb calorimeter and measuring the temperature increase. The energy available depends on what happens to the water produced from the combustion of the hydrogen. If the water remains as a gas, then it cannot release the heat of vaporisation, thus producing the Nett Calorific Value. If the water were condensed back to the original fuel temperature, then Gross Calorific Value of the fuel, which will be larger, is obtained.

The calorific values are fairly constant for families of HCs, which is not surprising, given their fairly consistent carbon:hydrogen ratios

[DAEDALUS]

" but I dont now what "stoichiometric" means." and you are "I am Technoman"

Don't get offended! Just seemed dicotomistic to me.

LOL Dennis, it could very well be that his login refers to his choice of music and/or club preference!

[I am Technoman]

yes it is because of music! well anyways My ECU needs some kind of oxygen reading on the front side. Im bored today so im gonna see what happens.

[Q45tech]

See us old guys [55] don't know modern music, the last thing I bought was a record---- oh a few 8 track tapes in the late 60s and some cassettees in the early 80's................books on tape now and NPR. My Q cassette player has been broken for 5 years no loss.

[I am Technoman]

Well I cleaned up the front o2 sensor with purple cleaner and shinned it all up. I placed it in the rear of my header so it could read all cylinders and not just 2. The car idles like a dream with no stuttering at all. I tested it on the road buy hitting it hard in 2nd gear and then letting off the throttle leaving it in 2nd and it did not go pop pop pop like it did before due to being to rich. I do not have my rear o2 sensor plugged in anymore but that’s ok the ECU can still see the front and now it reads properly.

[drjohn]

Sometimes you just have to experiment once in awhile to see what happens. Trial and error.

[I am Technoman]

Im not happy with this o2 sensor so I shall by a new one. I dont think it's reading fast enuff, But hooking it back up and placing it in a better location made my car idle much better.

[EZcheese15]

See us old guys [55] don't know modern music, the last thing I bought was a record---- oh a few 8 track tapes in the late 60s and some cassettees in the early 80's................books on tape now and NPR. My Q cassette player has been broken for 5 years no loss.

Yeah, Dennis says this as he has kazaa open with 30 techno songs qued. haha