Gutted cat Vs. Test pipe

[TConklin821]

Are there any advantages to one over the other? I know they may sound different, but other than that, will performance increases be roughly the same?

[D's Avant]

I would say just about the same and a HFC would sound much better and not stink. May get some odd pinging sounds with a gutted cat, I know I did on my I5 2.2 way back. Ran the HFC on my B5 and was very, VERY happy.

[TConklin821]

Yeah but a HFC is so pricey, lol. Pinging sounds? Hm, that's odd. I've had gutted cats in the past.

[seanj130]

Gutted Cat here.. No issues with it. No weird sounds..

[M-Hood]

A test pipe is going to be better because it will have even flow from end to end, a gutted cat is larger in the center which means there is going to be some turbulance in that area. This is why some people that gutt their cat usually install a pipe inside.

[coolgraymemo]

How I see it, the test pipe would flow better because it is a "pipe". It is mostly the same diameter.

The gutted cat would be different. Since it is shaped weirdly.



Quick search:

http://www.audizine.com/forum/showth...+Vs.+Test+pipe

[Turbwhistle]

The gutted cats cause pockets because of its shape which is said to restrict air flow slightly, and it is said to have a weird sound.

[TConklin821]

I may just get a TP, but I wouldn't be able to pass inspection, and a HCF is pricey.

[CCA4]

Trying to come up with a plan for this myself at the moment. Do you guys just have visual inspections or do they use sniffers? The Shell station I go to doesn't have AWD rollers so I'm thinking I'll be able to get away with a test pipe if I can keep the catalyst efficiency code goblins away.

[TConklin821]

In NY they visually inspect for a cat, and check all your codes/monitors.

[Turbwhistle]

Rear o2 spacers ftw! Havent needed to go to emmisions yet but if the just scan the car i am set.

[TConklin821]

Well I can just do the rear o2 sensor delete, that's not the issue. I want a TP, and I have no problem registering my car in another state if necessary.

[ECS Tuning-Audi]

The test pipe will yield more gains due to being all one size. Flow will be much smoother as well. A lot of people use cut the old cat in half and then weld it around the test pipe to make it look like a cat so it will still pass a visual inspection.

Jason

[nthomas33]

I hear the RAI test pipes don't throw a code, cause they have some kind of tube thinger on there. Sorry to bog you down with all the technical data lol :P

[Turbwhistle]

Rear o2 spacer ftw!! I dont know if i will pass emissions yet but i have no check engine light.

[FNK]

Cut your Cat and weld a tube instead.
A gutted cat, as stated before, will create turbulences from the edges.

So cut the cat, weld a tube and reuse the O2 sensor bung.

[Turbwhistle]

I dont thing the 02 sensor would work if you did the cat welded to test pipe thing. You need a small amount of exhaust gases to keep the sensor from going off. If you have the sensor where you get no gases it will go off any way. Your best bet is to get a hfc, test pipe and use o2 spacer, or just swap the cat on every 2 years.


Sorry about the double post before, i am using tapatalk and i have shitty service.

[M-Hood]

I dont thing the 02 sensor would work if you did the cat welded to test pipe thing. You need a small amount of exhaust gases to keep the sensor from going off. If you have the sensor where you get no gases it will go off any way. Your best bet is to get a hfc, test pipe and use o2 spacer, or just swap the cat on every 2 years.


Sorry about the double post before, i am using tapatalk and i have shitty service.

I think what he was saying is weld a pipe in the section where the actual CAT was, the 02 sensor bungs are before/after that area so they would still be in the exhaust flow. This would basically make it a test pipe that looks like a 100% OEM CAT.

[Turbwhistle]

Oh yes, i see it now, i was thinking a little diffrent the before and after the fake cat.

[myfairlady]

I have run a gutted cat with no issues for 70,000 miles, don't even get a CEL...

[TConklin821]

Stock cat around a TP, that's a cool idea. Sounds like a pain in the dick to fab up. And here inspection is every year, not worth the hassle of swapping every year.

[FNK]

Welding the old cat over the test pipe is an idea, but I was just saying you can cut the O2 sensor bug and weld it on the pipe. So you'll have a "test pipe" for 10$ish. The bung might set you back 10$, since you can reuse them, why not!

[M-Hood]

Welding the old cat over the test pipe is an idea, but I was just saying you can cut the O2 sensor bug and weld it on the pipe. So you'll have a "test pipe" for 10$ish. The bung might set you back 10$, since you can reuse them, why not!

The pipe would still need a flange on either end unless you are suggesting to cut those off the stock CAT and weld them onto the pipe too.

BTW the CAT has a bend in it so a straight pipe isn't going to be a direct replacement. Cost more then $10 to make a test pipe seeing that it takes 2 flanges, 2 bungs and a pipe with the correct bend in it to make one. Not to mention the welding material to weld it all up.

[viceprp]

You can pick up a used TP for $90.

[TJN0923]

Just buy a test pipe and find a small shop around your area that will pass you. It's always good to have hookups :)

[bw86]

You can pick up a used TP for $90.

Yep, I picked one up awhile ago for around that same price.

[Turbwhistle]

I payed 90 for an ebay test pipe. Not sure if it was/is good, but it is doing its job.

[coolgraymemo]

You can pick up a used TP for $90.

I regret passing up on a VMR Test Pipe for $60.

[M-Hood]

I regret passing up on a VMR Test Pipe for $60.

Wasn't that just the Jeff Lee PSI test pipe?

[coolgraymemo]

This one was on CL. I don't think the person was a AZ'er.

I preferred it over the regular TP since it has the heatshield and looks like a stock cat.

[TConklin821]

Do you guys know if a standard TP will work with an o2 sensor spacer? Like one from eBay or something?

[Turbwhistle]

yes it will, i have ebay tp, ebay 02 spacer, and they work great. Make sure you get b5 a4 1.8t specific tp though.

[TConklin821]

Will do. Next I'll just have to make sure it will work with a FrankenTurbo, because I'm probably going that route within a year or so.

[flynnr]

buy a test pipe

sell your cat for $100 + to the precious metals place

enjoy a very, very cheap upgrade

[WaspB5]

?Question? I have a 98 B5 A4 1.8t. I recently upgraded to a ko4, 5 bar fuel pressure regulator, and some agressive GIAC software. The ko4 was faulty so i just replaced it w/ a new Ko4... i decided to upgrade to a 4-2-1 turbo header, and a Fast Intentions Test Pipe as well. Now when i start the car it idles rough starting at 2000rpms and then goes down to 500rpms off and on... not like it would with a vaccuum or boost leak but gradually... its very strange. I took the spark plugs out and they were soaked in gas? Also, the car wont stay running for long, and once it dies its hard to start again. We even unplugged the MAF Sensor to see if it would help... no difference. I installed an 02 Sensor spacer so there's no CEL. I havent the foggiest idea as to what the hell is going on. We've checked our work over and over.... a little help here, please???:(

[TConklin821]

You should probably start your own thread.