95maxrider

iTrader: (32)

I was thinking about this last night...I'm getting my exhaust cutout installed tomorrow, and it made me think about what effects it will have on the O2 sensors. I want to install the cutout in the y pipe right before the cat, which would bypass at least 1 O2 sensor. Would my car go into closed loop, or something to that effect if the O2 sensors weren't reading anything? I know Aaron has been using one for a little bit now, and I'm sure there are other people using them. I'm guessing that since I haven't read about this yet it's probably not an issue...but it made me think.

What do you guys think?

95maxrider

iTrader: (32)

Any ideas???

Also, besides my y pipe, my exhaust is stock, so my mechanic didn't really have a place to mount to cutout. I wanted it in the y pipe, but there isn't room. My next thought it to get a straight pipe and weld it into that. What are your thoughts on this issue?

Aaron92SE

iTrader: (128)

I highly recommend getting a straight pipe and welding the cutout in there. When emissions time comes around, just swap in the cat and you're set. There won't be any change in your setup and it will be easy to get rid of the cutout if you change your mind later on.



You're right, the cutout won't fit in your stock Ypipe. It will fit fine in a testpipe. And it should fit after the cat, in the Bpipe. But you don't want a cutout AFTER your cat. That wouldn't give you the best results.

I wouldn't worry about the o2 sensor at all if the cutout is after the sensors. My car only has one o2 sensor (not counting my wideband o2 sensor ). So I didn't have to worry too much about sensors since I just did the testpipe cutout dealy.

95maxrider

iTrader: (32)

Yeah, but I'm pretty sure us 4th gens+ have more O2 sensors, with 1 after the cat. I could be wrong though. Anybody know?

young1976

4th gen fed emission has an )2 sensor after the main cat. 1999 CA emission and 5th gen CA emission does not have O2 sensor after main cat. That's all I know. I think the Fed emission cars have it .

nismology

iTrader: (8)

4th gen fed spec has 2 in the y-pipe and 1 after the cat.

95maxrider

iTrader: (32)

Ok, so we 4th gens do have a sensor after the cat. How much do you think it could effect the timing and stuff in the engine if it doesn't get any info?

young1976

probably not too much considering the cutout just lets exhaust leave the exhaust pipe sooner. So in that sense it relieves backpressure, so you can increase your upper end. I'm sure there will still be some exhaust gas going into and through the rest of the exhaust so the O2 sensor will still pick up stuff. It might fool it into thinking there's not as much hydrocarbons in the exhaust and not give you any problems. I guess you'll just have to find out. It shouldn't effect timing. unless your engine knocks or if you're using lower octane gas. As for the fuel air ratios (power) you might gain because again, the 02 sensor thinks the exhaust is cleaner because a bulk of it is released already by the time it passes the rear 02 sensor after the Cat. Just what I think by logic... I'm no expert... Anyone with a definitive answere please make a comment.

Aaron92SE

iTrader: (128)

Well, I know a bad o2 sensor can really make the car run like crap. So, an o2 sensor getting no reading, I would say it's not good.

I think some 4th gens have a sensor IN the cat converter. I'm not sure which years those are. But I've never heard of a sensor being located after the cat in the Bpipe.

You can email "i30krab". Look him up and ask him about his cutout. He has a 95 or 96 i30 with an electric cutout like I have.

Anachronism

95-96 has an o2 sensor in the cat, 97-99 have it in the B-pipe behind the cat.

Aaron92SE

iTrader: (128)

Thanks. So that means that 95maxrider should be fine. You can just get a normal testpipe, weld an o2 sensor bung into it while you weld in the cutout.

I recently had to get an o2 sensor bung welded in my Ypipe for my wideband o2 sensor. The guy cut the hole with a torch and then welded the bung that I gave him. $40 to do all that on a lift at a mom and pop's muffler shop. I bet they could cut the testpipe and weld in the cutout for about $20 more.

But my friend helped me weld my cutout in my testpipe after I got the exhaust couplings from autozone. Then just drill a hole, weld the bung in and you're set. I would just try your best to put the o2 sensor before the cutout.

young1976

But doesn't that O2 sensor after the cat or in the cat(but toward the end of it) reads the exhaust after it's supposedly processed by the cat? So by literally removing the cat, that O2 sensor would think your exhaust is bad and throw a CES light signifying a malfunctioning Cat or something along those lines? That's how the CA spec y pipes work, it fools the ECM and removes the rear bank precat. There's 4 o2 sensors on our CA Emission cars. and the sensors after the precat essentially act like the one after the main cat on Fed spec cars. My thinking is if an O2 sensor can't get readings such as no readings or out of parameters then it's dead. But if it senses less of the bad exhaust it would just send that info and the ECM would think everything is working great if not realy good. I've heard of people just tying or hanging the rear (aftercat) O2 sensors in the air (not in exhaust) so the CES light won't come on. I guess that's when they remove all cats...

nismology

iTrader: (8)

The rear O2 sensor does nothing to affect the air/fuel ratio. The ECU uses it for diagnostic purposes to see if the cat is operating properly. You might possibly get a CEL, but the car won't run any differently.

Edit: And besides, at WOT when the ECU enters closed-loop operation(when you would be using the cutout anyway) the ECU ignores the signals from the O2 sensors so you should be good to go.

young1976

Then I guess his question is answered, don't worry about it, if the light comes on, then reset it...

Aaron92SE

iTrader: (128)

It's open loop that doesn't read from the o2 sensor. Not that it really matters. But you're right, when you're WOT, the ECU stops getting readings from the o2 sensor. So if that rear o2 sensor is strictly used for diagnostic purposes, I wouldn't even worry about welding an o2 sensor bung in the testpipe. Just let it hang in the air. I know there are plenty of 4th genners out there that have a testpipe. Just find out what they do with the o2 sensor. I think they either let it dangle or actually get a testpipe made for 4th gens with a sensor bung.

WSP has the best deal on a testpipe. Cheap, great service, and great quality. I think I got mine for $35 shipped.