Catalytic Converter removal.

[derekmitchell]

Hello audi men.

I drive a 2001 Audi a4 avant quattro with the 1.8t

I was considering just taking out my cat. I had no cat on my old trans am and I enjoyed it

Figure it wouldn't be that tough except the anticipated toughness of the bolts holding the cat and down pipe in.

So my one question is if i were to replace my cat completely with just a straight pipe would it run lean and what would I do with the 02 sensor? Just attempt to put it in the straight pipe or what?

http://www.amazon.com/97-05-Audi-1-8.../dp/B008DMFY8K


Link related, if there are better straight pipes point me that direction. Thank you.

[turbo_bootin]

Secondary O2 sensor does not control A/F ratio. Unless you have a larger exhaust, there's no point in replacing it with a catless pipe, just hollow the cat out.

[derekmitchell]

Whats the procedure on that?

[c0r3y.af]

The test pipe you posted should work just fine. ECSTuning also sells one that will work. You will need an O2 sensor spacer (42DraftDesigns sells one) for the rear O2 sensor to prevent a check-engine light.

[bw86]

Just get a testpipe and 02 spacer (search) and you'll be golden. I picked up a test pipe from the classifieds a couple years ago for $75. After that just get a chip and diverter valve and your car will actually have some balls.

Sent from my SGH-I747 using Tapatalk 2

[derekmitchell]

It looks like it comes with spacera doesnt it?

[freeloader700]

Secondary O2 sensor does not control A/F ratio. Unless you have a larger exhaust, there's no point in replacing it with a catless pipe, just hollow the cat out.

Don't do this...its a pain in the butt to do! you will then also have uneven flow due to the shape of the cat Get a test pipe, sell the cat or scrap it for $50-80 to a cat recycler

Just get a testpipe and 02 spacer (search) and you'll be golden. I picked up a test pipe from the classifieds a couple years ago for $75. After that just get a chip and diverter valve and your car will actually have some balls.

Sent from my SGH-I747 using Tapatalk 2

x2

However I didn't have luck with the spacer. Either my O2 is larger than others or the port is somehow smaller because I drilled out the antifouler and I could not get it to seat properly


Here clickity click This is in the B6 section but I am pretty sure this will work with B5 as well, someone else will confirm this

[c0r3y.af]

Don't do this...its a pain in the butt to do! you will then also have uneven flow due to the shape of the cat Get a test pipe, sell the cat or scrap it for $50-80 to a cat recycler

However I didn't have luck with the spacer. Either my O2 is larger than others or the port is somehow smaller because I drilled out the antifouler and I could not get it to seat properly

Agreed, don't hollow out the cat. Not worth it.

Not sure why you had problems with the spacer. I know a few people running THIS ONE with zero issues. Just picked one up myself. Screws right on, no problems at all.

[freeloader700]

$40 is a little more than I want to send on that right now. Thanks will keep in mind

[TylerDSAudi]

I just finished going through all this with my 2001 Audi a4 1.8T what I did:

Replaced my cat with a test pipe from eBay. Great qauilty and install was great! All o2 sensors went right in and I don't get a check engine light for over 100km, but I just clear it with my scanner. If you want but the $6 non foulers and do that mod to get rid of that. I need to do later as I ran out of time. You can tell it sure wakes the car up! If your looking for sound I didn't gain any, just quicker boost and little more power because of that.

I just got my car 3" straight piped yesterday and what a difference! Spool way faster, better power and you can sure tell it! It's alittle loud, but I love it. It will be getting a magnaflow muffler come soon here to quite it just a bit though.

You shouldn't have a problem with running lean or anything in mechical spec, just the check engine light and you smell more outside the car as usually the cat burns that off.

[QuattroGinger]

crap ton of companies make the test pipe. if you go ebay, just watch out for the position of the rear o2 as most ebay ones sit on top when it should sit off to side. i got ebay one and wrote guy about it. he send me free 90 turn spacer, however my new turbo setup came another test pipe with it in correct spot so i just used that.

[TylerDSAudi]

crap ton of companies make the test pipe. if you go ebay, just watch out for the position of the rear o2 as most ebay ones sit on top when it should sit off to side. i got ebay one and wrote guy about it. he send me free 90 turn spacer, however my new turbo setup came another test pipe with it in correct spot so i just used that.

We'll usually you want them on the top. My eBay one came on the side and now I can't use the non fouler mod because I can barly get my rear 02 sensor in because it is pushed against the block almost. I'm going to be rewelding that hole up and drilling a new one with a new welded nut so I can do the non fouler.

[QuattroGinger]

Odd I have plenty of room with fouler in mine

[freeloader700]

My o2 itself was not going to fit in the antifouler. I drilled it more that 1/2" it still no go. In order to get it to fit, I would be scrapping the inside of the outter threads so I gave up for a bit on trying to get it to work

[derekmitchell]

Well thank you guys. Got great responses that helped.

I plan on taking that cat out, putting in a test pipe and getting possible slight power increases and a possible profit with scraping that cat.

The main reason I considered this was because I had a trans am before and the smell of the engine running and the rough idle was loved dearly.

[c0r3y.af]

Well thank you guys. Got great responses that helped.

I plan on taking that cat out, putting in a test pipe and getting possible slight power increases and a possible profit with scraping that cat.

The main reason I considered this was because I had a trans am before and the smell of the engine running and the rough idle was loved dearly.

Good choice. You'll definitely notice a difference.

[freeloader700]

Awesome. You will definitely notice like cOr3y said, the throttle response is better, yeah get more exhaust sound and hear the turbo whistle a lot more..

Also, if you haven't already and have the stock airbox, there is sound dampening foam in the walls of the airbox(I believe yours does), rip that junk out and that will give more sound as well

I know what you mean about the smell, I have a built an 88 GT 5.0. That was good fun