What do you mean by perfect? Are you trying to eliminate the cat?

i bought a greddy evo cat back with test pipe, and while i was taking off the stock exhaust, i broke the o2 sensor. I was told to get a simulator since i'm no longer going to have a cat, and i need something soon, because i'm sure the car won't run right without anything there.

The rear O2 does nothing for adjusting fuel. If you can get a working O2 then I would get one. If it throws a code no big deal. Your A/F readings are going to be from the front O2 sensor.

Yes, the second O2 sensor does adjust the fuel mixture. And when I put my A'pexi full exhaust on I called A'pexi to ask what to do with the second O2 sensor. They told me to put it on, cover it and put it in the car to protect it. This was confirmed by a couple of exhaust shops as well. Before this I was running fat and the check engine light was on. After I put it in the car, everything is back to normal.

How would putting it in the car make things better? I really dont understand this because if what you say is true then if it is left on the car then and the car runs rich.....Why wouldn't it run lean if you put it in the car because you are sending 0% 02 signal to it? It does not make any sense. I know several people who run open exhaust and do not have any fuel problems (I.E. .93volts) which last time I check was normal operating perameters. I realize for tuning purposes 02 voltage is not a good indicator of "fuel problems" but it is a way to know if you are running excessively rich. The only thing that putting inside the car would do is keep the CE light from coming on.

Leaving it in the car lets the O2 sensor sense, clean air (double snake bite on the clean air). That is what what my car did, that is what my friends '99 GSX did, and that is what I was told. And keeping the CE light off so you can be warned about other things in your car is kind of important.

could we be more off-topic? I'm asking if anyone knows where to find the simulator. It's my preference to get a simulator over another o2 sensor.

GO here: http://www.casperselectronics.com/cgi-local/store/commerce.cgi?product=HID

I have heard mixed reviews on them.

Why in the world would placing the O2 in the car be better? It is merely a check sensor for the OBD-II ECM to verify cataletic converter function. It compares the two signals and verifies cat operation that way. I have ran a testpipe for over a year with no codes thrown. I know several people who run 12-11second DSMs with no 02 and no simulator that do not have any problems or CE lights. Get a pocketlogger and you can turn off the check engine light whenever you like.

thanks. Well, i guess i'll try running without it, but if i get a CEL, i'd rather get a simulator than another sensor.

I understand, I felt the same way before I got my pocketlogger. Now if I ever do get a CE light I can just turn it off .

well, just as i thought.. as soon as i started it up after putting on the exhaust, it threw a code and its running hella rich. :-/ I know that the simulator is just some form of resistor to keep the voltage optimal. Does anyone know where i could find a schematic to make something? Or- does anyone know what the optimal rear o2 voltage is? thanks!

Thats wierd. Unless the rear one is starting to go bad or something. The only time that it should adjust fuel is if it is bad. I have heard stories go either way on this, but if your having a problem I would go ahead and give casper electronics a call.