o2 questions....need some answers...

[syntax_erorr]

ok...this is something I have been thinking about every snice I rented a scan tool from murrays....anyway...the o2 senors are what the pcm really depends on to decide how much gas to give the engine right?(after it goes into closed loop mode anyway)...and the pcm trys to get the a/f ratio at 14.7:1 right? I have heard that that is a little lean(for emmsions concerns) for best performace...around 12.5:1 would be best ...again..not sure..only heard from someone.....so..would I get some gain out of sending a lean condition voltage to the pcm?...I know running too rich can be bad for you egine though...and I also know that if the pcm see's the same voltage from the o2 senor for more than a few min it starts to ingor it and throws a ses light....and also..is the o2 senor sending a restisted 12 volts to the pcm? or is it sending a resited ground to?....I tryed to sreach for answers to my question...but I couldnt' really find any...

[AllTheGoodNamesAreGone]

I dont know about the ratios but, I think that you are on par as far as how the system works in general..

It would be helpfull if you could let us know what you are trying to do w/ this information..

~Billy

[Camaro Bob]

He's trying to find a way to send a lean condition signal to the PCM to run more fuel into the engine to get optimal power out of it (raise from 14.7:1 to 12.5:1 for the a/f ratio)...also, in a way to not throw SES....am I wrong? I've been working on it for a while....it's not working out. It's causing more problems than gains. Reprogram...maybe it's possible. It's hard to do with such a computer controlled engine. Any of you guys got an idea? Hint?

[zlexiss]

It's probably going to be tough due to the curve that narrowband O2 sensors function on. That steep rise/fall right around 14.7:1 means you can't just bias the voltage by an offset. I'm not even sure you can use the narrowband output to reliably get close to a ratio that isn't 14.7:1, they were designed just for this ratio.

I suspect the full answer involves a wideband O2 sensor and a small black box. The black box reads the wideband's output, and outputs a voltage curve that looks as if it's a narrowband sensor. Except you can set the voltage swing around a custom desired ratio.

I can try to explain this better if I wasn't clear. As far as designing one, I'd guess a decent EE, given the graphs for narrowband and wideband sensors, could devise some sort of system that uses a lookup table for the translations. Multiple tables could be selected or uploaded to a flash to change the goal ratio. After that, it's all packaging..

-Jeff

[syntax_erorr]

do you happen to know if it sends a rested ground to the pcm? ..not 12v?..the senor sits in the header..which would be grounded...so I would think that it is a ground it is sending back to it..I can't believe that the senor makes between(.1-.9 volots(Ithink)) just from the change of air out side the headers to inside.........I would think that this would have to make a performance gain..I know that when the system is in closed loop mode and under heave acl. the pcm decides the pulse width of the injectors off of the o2 sensors...so if I was to send the lowest about of voltage that the pcm will read as a true possible output from the o2 senors that it would open the injectors longer...I believe the min is .1 for lean..and .9 for rich.(am I right on that?)....I dunno...I'm just really ready to try this out...but I'm still uncertain as the whole ground or 12 volts thing...

[zlexiss]

There's some good info on how things work here:

http://www.installuniversity.com/ins...to_tap_faq.htm

along with a graph of the O2 sensor curve. Some good info on air/fuel and how the sensor responds.

-Jeff

[AllTheGoodNamesAreGone]

ohh.. that link is pretty good.. that answered a whole bunch of my questions.. MAFT here i come!!

thanks zlexiss

~Bill