Why No O2 Simulators

[sparty116]

How come a '96 gts doesn't need O2 simulators when removing the cats? Any thing that I should worry about concerning the engine after removal? What do I do about the existing O2 sensors after I cut out the cat?

 

[BigCarrot]

I'm guessing that a 96 is OBD1, so it doesn't have downstream sensors. I emphasize GUESSING!

 

[1TONY1]

A 96 is obd2 just like later models, it just has a dumb computer that doesn't care about the rear o2's. After you get rid of the cats just leave the 02's pluged up and in the pipe as they are now and you will be fine.

 

[Jack B]

I believe the O2's care, because when in closed loop they are modifying the A/F ratio by altering the injector pulse. When out of range by 33% that is the typical reason for a "Service Engine" code. The question is why aren't they as sensitive and throw a code like the 99 and later.

 

[GTS Bruce]

On later obd 2 cars the 02 sensor upstream adjusts fuel mixture just like earlier cars.The down stream 02 sensor tells the computer wether or not the cat is working.A cat sym is pluged into the harness where the down stream sensor was pluged it and it fools the computer into thinking there is still a working cat there. Bruce

 

[sparty116]

Could I still put on the Roe O2 Sims to ensure I don't get a error code, or run too rich? The O2 sims say they are for '98 and newer. Does that matter?

 

[STUGOTS]

I would call Sean Roe and ask him

1 866 275 7326 #3

 

[Jack B]

Bruce:

early OBD2 cars also have two O2 sensors. My 94 (OBD1) had one, anything 96 and up has two. The question is why don't the 96-98 throw a code when you remove the cats/modify exhaust and the 99 and newer do.

I believe the OBD2 standard is any deviation (in closed loop) of greater than 33% from 14.7 for a prolonged time will draw a code. The standard didn't change for different model years, therefore, why do the newer cars go into alarm.

 

[GTS Bruce]

Here's a question.If early obd2 cars don't throw a code without cats.Will the pcm still screw up the fuel mixture and timing? Bruce

 

[Achilles99]

Bruce:

...The question is why don't the 96-98 throw a code when you remove the cats/modify exhaust and the 99 and newer do.

Just a quick clarification... 98's throw a code, according to Sean's website.

Sorry to hijack the thread, but I have a related question... I plan on installing hi-flow cats. Will I need to change the O2 sensors that were left on the car... ie, will they still work, or does running without cats ruin them? I guess I'll just remove the O2 sims that are on there now, and rewire the sensors. Hopefully, they'll still work. If not, where's the best place for stock 02 sensors?

 

[1TONY1]

Could I still put on the Roe O2 Sims to ensure I don't get a error code, or run too rich? The O2 sims say they are for '98 and newer. Does that matter?

Ok, In you first post you answered your own question. A 96 DOES NOT need sims. So why would you put sims on it to "ensure" you don't get an error code ?????? If you want to throw money away you can start me a twin turbo fund There is a reason that sims are for 98 and later....hmmmmm.....I wonder what the reason is.

The front o2's do the a/f and the rears are just supposed to make sure the cats are working.

 

[Joseph Dell]

so where can one buy an O2 Sim? Or can I just make one with some bubblegum, paperclips, and a resistor from Radio Shack?

Any help would be appreciated... I'm thinking about going the no-cats route...

JD

 

[Achilles99]

JD,

You can buy the sims from Sean Roe. Better yet, you can buy my sims They've been on the car for less than a year. I'm putting hi-flow cats in, because the car is too noisy and smelly to use as my daily driver. I'll be going back to the stock 02 sensors, so I won't need my sims.

If you want, you can have my old straight pipe setup. It has big tips, borla bullet mufflers in the side sill, and a muffler delete. The only thing is that it uses stock 2.5" piping. It's LOUD, and the side sills stay cool to the touch, though. I HOPE the hi-flows stay as cool!

I'm switching to a 3" exhaust with hi-flows (the hi flows were 3", so I figured I'd take this time to switch to a 3" catback).

Let me know, because otherwise I'd be throwing the current straight pipe into the dumpster

 

[Achilles99]

BTW, if you want to hear the setup with no cats/rear muffler delete/borla bullet mufflers, let me know... I'll probably be removing it within the next few days!