Alan 91 C2

The below pictue shows what 18" of the exhaust pipe, before the cat, looked like Almost closed .

J1720

Wow. Never seen that before.

Mighty Shilling

I've heard of that, but never seen it. That's insanity!

Alan 91 C2

I removed the collapsed sections and will weld the pipe back together. Bought the car early this year. Interested in performance after the blockage removed.

Thom

I saw that on a cross pipe. The turbo would not spool.

Alan 91 C2

Cross pipe looked good. Used a 1" rubber hose inserted up to turbo. When i tried to push the hose in the cat pipe, no joy. After a few minutes of sawsall the problem was identified.

Tom M'Guinn

That's the best picture yet of the infamous collapsed downpipe! Yes, you should feel the difference! Just going from a cat to test pipe is noticeable. I'd take a close look at the cat portion for melting/blockage if you are planning to use it. If you don't need to retain the cat portion, or if a new higher flow replacement will suffice, you'll notice it even more.

lart951

I have seen that in both crossover and down pipe.

dillon410021

why is it 2 piece pipe(2 layers)?

mclarenno9

It's just a different way of insulating a pipe basically.

toddk911

Yea get the cat out at the same time and with the collapsed pipe out you will swear its a whole different motor under the hood. Lol

LuigiVampa

Can someone explain how this happens?

TonyG

Seen it many times, just not to that degree.

It's commonly known that buying a real test pipe (like a Bursch) makes a much larger difference than just getting rid of the cat. And this is exactly why.

TonyG

toddk911

How does messing with the cat or test pipe have anything to do with causing collapsed down pipe or crossover?

Also test pipe is test pipe. Be it 3 dollars or 300.

Tom M'Guinn

The collapsed down pipe is part of the cat converter. When people hollow-out there cat, they think they are getting the same benefit as a test pipe. Instead, they have a restricted pipe with a partially collapsed inner wall with a nice hollow cat in the middle.