Can some explain how an O2 sensor works ?

[Ozark Hauler]

I was wondering how an O2 Sensor works ? Does it work on some sort of electrical resistance / air flow /exhaust temp ?

The reason I'm asking is this . I've heard how our engines computers go a bit crazy with cams, exhaust changes with the decreased back pressure . Somewhere or someone told me that installing a freer flowing exhaust will fool the Computer into thinking that a "Lean Condition" exists and throws more fuel to the injectors , is this true ?

I've got other questions and an Idea but I'd like to hear about this first , especially if electrical resistance plays a role in it's operation .

Thanks ,

Steve

 

[BLADE262US]

Hows this Steve ?

http://auto.howstuffworks.com/question257.htm /emoticons/[email protected] 2x" width="20" height="20" />

 

[Ozark Hauler]

Thanks , Cool site ! It clears it up for me . Hang in here with me . I may be way off base but it won't be the first or last time !

What I was thinking about when I first posted was when a cam , exhaust and lets say a cold air intake was added to a speed density system the ECM can't handle alot of changes . I've seen that mentioned alot here, so I was wondering if the air charge is altered by the cam exhaust etc. and the O2 sensor was sensing the change and throwing the info to the ECM (is that the right description?) and it's trying to compensate by chucking too much fuel into "the mix". Do you think there may be some way to throw some resistance into the signal from the O2 sensor to "fool" the ECM ? ( my idea was a variable resistor-kind of like an adjustable proportioning valve for brakes ) ( also a Stereo Volume Control is a resistor ) You'd need one of those on-board digital units that has a read out of the real-time mixture that's being burned . I'm assuming (dangerous territory) , that something would have to be done with ignition timing too . But aren't there units for racing that can advance/****** timing for NOS systems ? Maybe I have too much time on my hands !!

Steve

 

[BLADE262US]

LOL no problem Steve feel free to ask any questions you want here NO ONE will give you a hard time about anything . You are correct in the speed density system not likeing changes . The O2 sensor is just giving input to the EEC to try to maintain the magic 14.7 to 1 ratio . The reason it doesnt accept change that well is because it is preprogrammed with all the characteristics of the motor such as mechanical timing , volumn of air intake and such . By mechanical timing I mean it expects that at a certain degree of crankshaft rotation a given valve is going to be open a given amount for a given duration it doesnt know any better and that is what it has been told it has to work with so the timing curve and fuel curves are all based off that . Now when you put a cam in that is outside of that range it is still working with its preprogrammed values and things arent happening when they should so generally the motor produces less power than it did with the stock cam . Same happens if you use a 302 computer for a 351 it may run but its going to be lean because the preprogrammed air volumn is off . A mass air system actually measures the amout of air coming into the motor by means of a heated wire running through the middle of a sensor mounted in the air intake tube the more air coming into the motor the cooler the wire becomes which changes the resistance value generally the higher the temp the higher the resistance . This system of measureing air is why the mass air system can handle about any mod you want to do to the motor . There are things you can do with the speed density system do a search on TWEECR and you should find the software and the special cable for reprogramming the EEC yourself its not really easy to use and it is easy to mess it up so make sure you back up a copy before you play with it . There are forums dedicated to this unit so there will be help available . Another item of interest if you want to get into this kind of thing is megasquirt.com it is a stand alone EFI controller that is all open based again forum supported so there is help . With this system you can do pretty much anything you want for a fuel map and they even have it controlling the ignition now so its a very good system but alot to learn . /emoticons/[email protected] 2x" width="20" height="20" />

 

[BroncoJoe19]

do a search on TWEECR and you should find the software and the special cable for reprogramming the EEC yourself its not really easy to use and it is easy to mess it up so make sure you back up a copy before you play with it .

Blade, Excellent response!

LOL, Spell checkers don't correct words that are purposely misspelled.

I did a search on TWEECR and found a number of links to it. So now I don't know if you MEANT tweecr, or if you meant tweecer

http://www.tweecer.com/