adding a resistor to the o2 input wire

[guest001]

I've seen many threads and post on adding a resistor to the IAT input wire, or whatever, or IAT mods, but that doesn't make any sense to me. Isn't the o2 sensor then end all, final adjustment to the fuel. which makes sense cause why the hell is it even there.

I can't take the entire credit for this, but it sounds like it would work. I have an older one wire o2 sensor on my car so that's what I'll be talking about. but if I were to add a resistor to that wire, which size is the question, it would lower the voltage to the ecu and it would lean out the mixture.

I actually have a wbo2 sensor, so I could throw a random resistor in there and get a good idea of how lean it is and vary the resistor accordingly.

It makes way more sense then attempting to adjust the fuel maps, because when the o2 is work its uniform and steady, or consistant as hell, way better then any attempt to lean out the fuel maps so far.

[guest001]

maybe this wouldn't work. cause the o2 sends a voltage of 0-1 to the ecu. is 0 or 1 rich cause if 1 was rich it would lower its actual output and add more fuel.

[n0rt0npr0]

right. It wouldnt' work. goto http://www.eagle-research.com/ to buy a device that will adjust your o2 sensors output

[guest001]

ok...... what the hell is that???


ok, then is the an electical device that would increase voltage?

I'm correct about the iat mod though right? cause if the computer is reading load and rpm, then getting fuel maps from the computers memory. then that duty cycle or fuel value is modified by the iat. at this point fuel is in the motor. it would take the next cycle of the engine for the o2's input to be a variable.

[kamesama980]

yes, the IAT sensor mod is just a resister and works because the IAT is a thermister... temperature varied resister.

[Hateful]

not sure which idea I like better; Lying to the o2 sensor or burning water.

[guest001]

yeah, but the question is how does the o2 actually work.

the engine would have to go throw one cycle for it to even get a reading and send the input to the ecu. so, the iat would affect the a/f ratio the first time. then on the next cycle does the ecu throw the input from the o2 into the calcualation, ONLY if your still in the same rpm/load on the fuel map. if the load/rpm changes its not going to correct it again the first time.

but I'm guess that the computer saves this info and use it next time, which would very!!!!! quickly make the iat resistor mod not do anything. and for only one trip.

the only way to do this without actually adjusting the fuel maps w/ the o2 disabled is to modify the o2 input some how. if 0 voltage from the o2 is lean and .9 is rich. you would need a device that increases voltage by .1 increments.

[kamesama980]

yes, the o2 sensor is used to adjust the whole fuel map over time, NOT for instantaneous response.

[maxxgraphix]

The O2 sensor puts out a DC voltage based on the amount of O2 in the exhaust stream. The CPU monitors this in real time at ??? cycles per second. You can watch the readings change on an advanced scan tool.

If you really want to %^&$ with your air fuel ratio, get your CPU chipped so that you can adjust the maps.

Placing ohms in the O2 circuit will just screw things up. Too lean can also result in less FE and fubard engine.

[guest001]

I do have a chipped ecu. I've been adjusting my fuel maps but it kinda complicated to get it really dialed in. adjusting something that's more precise would make it way more linear. adjust the maps, it really hard to get it to a a/f across the whole driving range.

I have a wbo2 and with the o2 connected the a/f is money. the stock o2 and computer do a great job of keeping the a/f really close to 14.7 . I figure take that same accuracy and slightly modify it or trick it. hell the majority of aftermarket fuel controller do the same thing tricking the computer.

[guest001]

Originally Posted by kamesama980

yes, the o2 sensor is used to adjust the whole fuel map over time, NOT for instantaneous response.

i dunno, it seems like it does it pretty fast, cause I disconnect my battery (which resets the computer) to install eeprom chips in my computer with new tunes and when I have the o2 enabled the a/f quickly goes to 14.7 or really close to it.

maybe its just my car, cause I know there such a thing as drivability issues after resetting a ecu or disconnecting battery. not that I've really seen, but it is in repair info.

[guest001]

is there not such a device or what??

I'm going to school for auto tech. and one of the books has a chart in it showing that you get better mileage with a leaner mixture. from what I've read it seems that 14.7 is just for emissions.

no, wait, why the hell would a leaner mixture cause higher emissions???

[Nate R]

Originally Posted by guest001

i

no, wait, why the hell would a leaner mixture cause higher emissions???

Higher NOX.

[RoadWarrior]

Ummm backwards thinking alert...

The sensor reading lean does not mean the car will run lean. It means the ECU will add fuel to get it richer again. So putting any resistance in there will actually make it run richer.

You wanna fake it out and run lean as hell, get a 1.5V alkaline battery and a 2 silicon diodes, connect the 2 diodes in series to the +ve of the battery and run that and a lead off the negative to the O2 sensor inputs on the ECU... But the fact that the O2 is not cycling either side of stochio or "switching" will probably clue the ECU something is wrong and it will fault it.

[bobski]

A resistor would be a bad choice of component anyway... Resistors limit current, not voltage. The O2 sensor produces very little current, so you would need to use a very high value in order to see a voltage drop across the resistor.

Even if you do manage to adjust the voltage somewhat, it would actually make very little difference in the air/fuel ratio. If you look at the response curve of a typical lambda (narrow band) sensor, it's flat up until something like 14.5:1, then takes a steep dive, ending up flat again by around 15:1. You simply can't tell much from the sensor output beyond that range of air/fuel ratios. So, even if you find a way to offset the sensor voltage, you still won't be able to go beyond that range of AFR readings... You would be feeding the ECU your false sensor readings without actually knowing what the oxygen content of the exhaust is. If you wanted an air/fuel ratio of 17:1, you would be shooting in the dark... Your sensor would simply be telling you the air/fuel ratio is somewhere over 15:1. Your signal tweaking circuit wouldn't know when to switch from 0 to 1 volts without a real reading from the exhaust stream.

What you need is a sensor that will give you readings for a wider range of air/fuel ratios - A wide-band sensor. Your best bet here is to use a wide band controller with an adjustable simulated narrow-band output. That would simply let you tell the controller to put that 14.5-15.0:1 window at 16.5-17 AFRs. That's well within the wide-band's operating range, so you'll be producing the fake signal based on actual readings from the exhaust stream. When the oxygen content in the exhaust shows the AFR at 17:1, the wide-band will actually read it as 17:1 and flip that 0 to 1 volt simulated output, where as the circuit using a narrow-band sensor would simply read "something over 15:1" and have no clue other than that.