Cyrus951

Shouldn't the head of the test pipe connect to a flange (I think that's what it's called, I'm talking about the 3 bolt connector on the head) that is coming down from the turbo downpipe? My system has no flange, it's been welded on..
As you can see, the new cat has been welded on by the PO..



If you look closely, you can see that the cat has been welded on to the pipe coming from the turbo downpipe. Do I need to order a special "flange" or just take it to a shop and get the head of the pipe welded on?

toddk911

A shop won't touch your exhaust unless they are putting a cat on after they are done. You would have to find someone wiling to do it "on the side"

Eyal 951

its welded from the factory like that. all our cars are like that.
~Eyal

Ben Z.

I think you are not looking at it quite right. The flange connecting the cat pipe to the downpipe is most probably fine, you just need to look farther forward and up (towards the turbo). The downpipe isn't very long. Go check it out again.

Claus Groth

The test pipe bolts to the turbo downpipe, up above the area where the O2 sensor is. At the back, it bolts to a 4-hole flange after the cat.

Also, please PM me.

Danno

Yeah, unlike other cars with a flange before and after the catalytic, the 951 has the cat welded to the middle section of exhaust. The flanges are at the end of the turbo downpipe and the beginning of the cat-back section. When people say "testpipe" here, meaning a catalytic bypass, they are really referring to a completely new middle-exhaust section that has no catalytic converter installed. So you can get something like the Burshc "testpipe" for $220 which is a complete 4-foot long section that bolts up in between the turbo downpipe and the catback.

I've still got cat-bypass pipe from my Supra if anyone wants one. It's an 18" section of 2.75" pipe with a 2-bolt flange on each end. Installing it was simple, undo 4-bolts, drop catalytic converter, bolt in bypass pipe. If only Hans and Frans engineers actually worked on cars, it would've been a lot easier on all of us.

Cyrus951

Thanks, I was looking at the piping the wrong way.

Claus, I sent the PM.

Eyal 951

cyrus, are you still looking to buy an LBE, I have one for sale.
~Eyal

PorscheDoc

So why can't you just cut the cat out, and weld in an exhaust pipe of the same length and diameter as the existing pipe? Seems like a very cheap way to do it if you have a welder. Maybe i am missing something here.

Danno

"So why can't you just cut the cat out, and weld in an exhaust pipe of the same length and diameter as the existing pipe?"

Not a problem and a lot of people actually do it that way. Just that not everyone has a welding-torch in theri garage. It's also illegal for automotive shops to do that kind of a procedure as well and they can lose their license and face stiff fines. At my last smog-check a couple years ago, I had to go to an official State of California inspection station and they even pulled out a dental mirror and checked all around the welds to make sure I didn't weld in a bypass pipe. I've seen cops look under cars that have modified exhausts as well. I think the fine is around $1500 for removing a cat. So the really stealthy procedure would be to weld in a cat-bypass pipe internally and keep the entire outer housing. Or even better, get a testpipe and weld on the outer catalytic housing (that way the flow is uninterrupted on the inside).

Sounds like a project for the various wrenching societies that are popping up... "Ok class, today's topic is 'Getting Around Smog-Emissions Laws 101'"

Eyal 951

Danno, cat removal is something i wanna do before i get my car up on the dyno, so it can be tuned that way. (does it make a difference?) I'm considering just gutting a cat and having mine as a spare. is it worth it to source a used test pipe instead?
~Eyal

OriginalSterm

a test pipe gives you better flow through the exhaust than a gutted cat. the sudden change in diameter can cause large boundry layers and turbulent flow, which can create some added back pressure (bad) that wouldn't be there with a straight pipe.

toddk911

Call around to some of your local performance shops. You might find someone willing to do a side job for a good price. I got a full 3" exhaust done from a guy for 250$ labor, 100 parts.