Interesting O2 Sensor Question!!!!!

[AnthonyR23]

On my aftermarket PYPES High Flow Catalytic Converters that I welded onto my x pipe there is a place for 02 sensors and there was also a place for the 02 sensor's close to where the original 02 sensors go on a regular H pipe.

The Cats came with plugs for the o2 sensor holes.

If I take those plugs out, put them in the holes where the o2's are right now, in the original location, and move the o2's down to the cat's, technically part of the cat but after the cat. Would my car better adjust the a/f mixture for an emissions test?

One other quick question is, you know how on alot of offroad x pipes, there is still a tube for the smog tube air pipe. I still have my smog pump hooked up. It is close to the x in the x pipe. The only place possible to weld on my cats was on the straight pipe on the offroad x. This is before the smog air tube. I guess the cats are supposed to be after this air tube. But I think I read somewhere that the newer cats are different and don't need air from a smog pump. Is this true, and should I be worried about this or do you guys think it is fine.

Thanks!!

 

[BlownFiveLiter]

Your readings would likely be off if you put the sensors in the cats because the sensors wouldn't get warm enough. I bet the plug holes on the cats are actually for air tubes to enter them. The cats I put on my old 90 GT had air tubes that came off at about mid-cat.

 

[AnthonyR23]

No they are definitely O2 sensor bungs. If you look up Pypes Catalytic Converters they are actually listed as with o2 sensor bungs and caps. I agree that the readings could be off. I guess that's maybe what heated o2 sensor's are for?

Guess that's a good question, heated o2 sensors possible on an odb1 for after cat use and emissions test instead of where it is now?

 

[AnthonyR23]

I'm sure there is something that can be done for this other than tuning the eec, that would account for the reduced o2 output voltage because of the temp difference by moving the o2 further down the exhaust pipe. Eg. instead of from .1 to .9, lets say its 0 and .8. The output voltage would still be linear, just might loose the two further ends, eg. closer to .2 or .8.

So if the o2 sensor operates best at 600 degrees and is placed at a certain point, does someone know what the temp drop is approx. for long tube header o2 adjustments using tuners' like the tweecer? Or even better voltage drop?

Is there any products out there that are more mechanical like plug in for long tube headers and o2 relocation that accounts for the change in temp and voltage drop? Or do people just make these adjustments to the eec?

Wish I had the lab at my old job with function generator, then I could play. I may dig out my old electromechanical and electronics program, with digital lab. Cause it would be sweet if you could just make a simple circuit that would allow you to move the o2's down a bit further to account for the air coming out the o2's, which would probably help emissions.

 

[Foxfan88]

I'd just keep the o2 pre-cat and let the EEC do its job, and the smog pump and cats will do their, the air from the smog pump will make the o2 read leaner and then the EEC will be trimming fuel in CL to a false reading. and probably would be a tad on the rich side. I dont know of any way to account for the extra air from the smog pump. But i dont see a reason putting the o2s in or after the cat.

I also think you would run into more of a HEGO delay problem as distance increases from the engine. And also it doesnt seem that the o2 should have a problem staying hot. The heaters keep it warm and the exhaust should keep them pretty hot. I dont think moving the o2s back a bit will cause any issues. Perhaps if you moved them to the rear of the car or something (who would do that?) perhaps it would.

If possible just get some bungs welded in the stock location and run them there and plug off the holes in question on the cats.

 

[HISSIN50]

If it was easy to tune around O2 relocation, guys with LT's who do their own tuning would not have to idle in open loop (they could rescale their O2's for the relocation). The O2's fluctuate quickly from rich to lean. When they're not hot enough, they lose range. This cannot be scaled around (if they had a constant reading, not back-and-forth, then maybe you could do something).

If the cats have O2's, maybe they're for OBD-II cars with O2's to monitor catalyst performance.

 

[AnthonyR23]

It was late when I made this post and was just thinking about my emissions test, but agree, def. not practical at all. Really ideally a wideband o2 with controller would be nice, even without a tuner at the moment. I sold my EEC Tuner as I don't like it. But am thinking that before getting a tuner a wideband would be useful just to get the right fuel pressure and to verify things like how my actual o2's are working at trimming/scaling the fuel. Don't mind my late night thought posts. I am going to tone it down.

I do have a new question, I actually have time this weekend, and am going to my o2's off, car is jacked up right now. And was reading a method of testing the o2's with a torch. I have 4 o2's and am going to use this method to test them. I have the link on my laptop, it's really interesting and all about o2 sensors. Has to do with hooking up a meter to the o2's on a workbench, then applying heat to the o2 at the with the torch, apparently within the first so many seconds it should read like .6 or something, then after 20 seconds should either go up to like .9ish or something, then with the heat off should quickly drop down to .1, on then off with the torch and it should fluctuate. Anyone know a good method like this for our 3 wire o2's? With details on the wires, think there is a white and two black or other way around. Help with this would be great!! Thanks guys!