O2 simulator

[1sickbird]

ok i recieved the PaceSetter Exhaust Ceramic-Coated Long Tube Headers with emmision fitting and Texas Speed 3" CAT - Y Pipe System For Long Tube Headers (fits Pacesetter, Hooker, Jet Hot Headers!!) *not CARB Certified!! yesterday. my question is do i have to make my own hole somewhere on my y-pipe for o2sims ? and do i need to buy O2 Simulators ? i just don't get it about this type a thing (O2 simulators) please some explain it to me how this thing works and how to install it. i really appreciate your helps
thank you

[Z Ya Later]

O2 sims are little boxes that you plug into the harness where the post-cat O2 sensors would plug in. Here's a pic...



I've never installed them myself (since I don't have any post-cat O2s), but I believe you would simply plug them in then tie them off out of the way of the exhaust. Mind you, this setup will not pass the visual SMOG inspection, so be forewarned. If you are going to run all 4 of your O2s, you will need 2 sensor bungs welded into place and most likely 2 harness extensions as well. Both are pretty cheap and the bungs can be put in for ~$15/piece by an exhaust shop. Hope this helps.

[1sickbird]

steve i dont thing i have real cats because my y-pipe says no carb certified i asked my friend no carb certified = ory and he said yes. i don't know if that true or not and seems to me o2 simulator is a choice. do i really need o2 sims ? because i hope i can find a "friend" to mske my car pass smog. oh 1 more thing i don't see anywhere to plug those thing in my cat or y pipe
thank you steve

[MN6WS6]

Your post-cat O2's should be easily spotted. One will be near the "hump" in your floorboard under the car, near the second cat on the passengers side. The other one will be at the back of the heat shield for that second cat. When you take the stock stuff off, you'll find them.

I see people on ebay that sell a hardwire-type O2 sim, and it looks like just a simple resistor that does it, similar to what you need for a skip shift eliminator. If I could get the resistance value, I could build O2 sims for next to nothing. They sell on ebay for like $10 shipped for a pair, so I know all it is in there is a nickel resistor with some heat shrink that somebody is making $9.90 minimum a pair. And yes, they are NECESSARY unless you program the rear O2's out with your own software or through a tuner company.

[Kevin - Blown 95 TA]

Maybe all you gotta do is supply 450mV to the PCM input to make it think the cats are working. Never tried it though, but it's going to be something along those lines. So you make a voltage divider out of a couple of resistors and the pcm sees the voltage it needs to think everything's hunky, and you're good to go!

[fastTa]

I have a feeling 1SickBird is thinkinng that he can just replace the FRONT o2's with sims. Obviously he doesn't want to do this unless he plans on tuning without them, which I doubt. He needs to get some o2 extensions so that he can place the o2's for each bank on either side of the header right before the collector. Pacesetter's can be ordered with or w/o the o2 bung I believe. He is going to have to get bungs welded in if he doesn't have them.

[1sickbird]

I have a feeling 1SickBird is thinkinng that he can just replace the FRONT o2's with sims. Obviously he doesn't want to do this unless he plans on tuning without them, which I doubt. He needs to get some o2 extensions so that he can place the o2's for each bank on either side of the header right before the collector. Pacesetter's can be ordered with or w/o the o2 bung I believe. He is going to have to get bungs welded in if he doesn't have them.

i'm confuse of the name and what o2 extensions for , is it the one connect to the header or the one connect to y-pipe after cats on stock setup? because the y pipe i got there is no hole for anything so do i have to make hole for o2sims? then again sites says O2 sims in for off road only thats makes me wonder do i want to make it off road or not.

[MN6WS6]

Your car has to have the Sensor 1 O2's or you're going to have nightmares. Your car will also run in open loop all the time, which is crappy power.

The primary O2's are also known as the pre-cat O2's. They are the ones that actually tell the computer what the fuel/air ration is. The post-cat O2's are secondary, and they only tell the computer that the cats are there and are working. They send out a variable signal, but it is pretty much within a very limited range so the computer knows the cats are doing their job. An O2 simulator is just a plug-in module that sends out that single voltage all the time, so whether or not the cats are there, the computer thinks they are.

O2 extenders are just 18-24" long wires with connectors on both ends that extend the length of your factory primary O2 wiring. Most long tube headers have the O2's way back, and the factory wiring can't reach it. So the extenders allow you to run the primary O2's much farther back from the motor than factory, so that you can run long tube headers.

[casey02ws6]

With cats you run 4 o2 sensors - 2 per side - 1 before the cat and one after the cat. If you are running without cats (ORY) you will only be using 1 per side. That 1 per side will connect to the wiring harness closest to the front of the car (the one that was in front of the cat in the stock position). The stock wiring harness will not reach from the stock position to the position on the long tube headers - this is why you need the extensions. The o2 sims do not connect to the y-pipe or header at all. They connect to the end of the 2nd set of wires closest to the back of the car and are kind of like a "cap" on the end of the wire. You then just tie them up somewhere under the car. I did not buy o2 sims - since I had to have it tuned anyway I just had the tuner take the 2nd set of 02s out. Your car will not pass smog without cats. If you are worried about that you should get a "catted y-pipe" rather than an ORY pipe.

[casey02ws6]

I see you got the catted y-pipe - I still do not think you need that 2nd set of o2 sensors but you could easily have the bungs welded up for them.

[1sickbird]

wow that was awesome and thank you all i know what i have to do thank you alll so much.

[MN6WS6]

You know, I just thought of this, I have real O2 sims on my car, and I have a Carchip EX that I can monitor the rear O2 sims with, so I just may try the build-them-myself deal. If I can make them cheap, I'll make a bunch and sell them to everybody on the cheap. I'm sick of seeing people charge $50-75 for O2 sims if it's just maybe $5 in parts retail including the solder, wires, connectors, etc.

[Injuneer]

For the after-cat O2 sensors, the PCM performs the following diagnostics:

P0137/P0157 - Heated O2 sensor circuit low: Circuit continuity - detects an O2 voltage stationary lean (low signal voltage) condition. Code sets if O2 sensor voltage stays below 40mV

P0138/P0158 - Heated O2 sensor circuit high: Cirduit continuity - detects an O2 voltage stationary rich (high signal voltage) condition. Code sets if O2 sensor voltage stays above 930mV.

P0140/P0160 - Heated O2 sensor ciruit no activity: Circuit continuity - detects an O2 circuit open. Code sets if sensor voltage remains between 391-491mV.

P0141/P0161 - Heated O2 sensor heater circuit: Detects a malfunctioning O2 heater circuit by comparing time to O2 activity to a calibrated threshold. Code sets if O2 sensor time to activity exceeds a lookup table value as a function of average flow rate.

So.... you need a device that supplies a variable voltage, fluctuating over the range of less then 391mV to more than 491mV, and which provides that signal fairly quickly after startup.

[Kevin - Blown 95 TA]

...
So.... you need a device that supplies a variable voltage, fluctuating over the range of less then 391mV to more than 491mV, and which provides that signal fairly quickly after startup.

So what do you think is in a sim that does all that and is still cheaper than a real O2 sensor? Maybe somebody needs to open up a sim and see what's really in there. Apparently they work, right? I have a hard time believing they are that sophisticated, but I've never really looked at one.

[MN6WS6]

I'm going to run the Carchip in my 98 Astro tonight and see what the deal is. It still has factory rear O2's in it, so we'll see. When I get my Firebird out of the garage (after all of these stupid hurricanes get done coming in down here) I'll run it in the car with the O2 sims and see what the difference is. I'm pretty sure it's just a simple resistor setup with a constant voltage, because it seems it would take an elaborate setup to make a constantly changing voltage output like that.