chapstic951

I am looking for a cheap used catalytic converter to salvage for the flange? Anyone have one they want to unload for a song? I want to keep mine intact just incase. I could pick up if local.

Lorax

I have one, but i don't know how much they go for. Mine was taken out 15 years ago and is basically new, so you might be better off finding a trashed one..

let me know

chapstic951

Ryan,
Yeah, I would feel bad ruining a working cat. I am doing some research regarding the cat and since I have not been under my 951 recently I don't recall something. Can you tell me if the oem cat is a weld in or bolt on and slip in? If it is a weld in Iwill just cut it out and weld in a straight pipe.

-Steve

jacklet

weld a straight pipe in

potent951turbo

What flange are you working on? The wastegate connection, downpipe, or the connection to the catback?

chapstic951

I didn't do my homework before posting. I was looking at the bolt on cats that aftermarket exhausts offer and assumed it was the same on an OEM exhaust. I will go sit in the corner now.

I am looking at removing the cat and putting in a straight pipe for fun and maybe even remove the muffler. I have to take the exhaust anyhow to install a WBO2 sensor bung, thinking while I have it off, "what else can I do?"

kasturbo

I've got one, I'll sell for $20, but not sure what to do about shipping.

chapstic951

Kevin,
I just took my exhaust out and noticed that the cat is welded at both ends making more sense to just have straight pipe welded in. Thanks for the offer though.

-Steve

chapstic951

Deviating off my own topic. I got the bung welded in a la Midas. Unfortunatly they could not replace the cat with a stright pipe. Apparently they are not allowed to modify emissions equipment.

So I got to thinking, what if I take a long pipe and break out the honeycomb inards? I cannot find the past posts regarding doing it ghetto style. Pros? Cons?

rberry951

I proposed this same question a number of years ago, the answers I got from the 'experts' were not promising. And made sense. If you just ram out the cat material you end up with a funky chamber where exhaust does not flow through well. Creates back pressures and strange flows. So I proposed slicing the cat open, removing said material and welding a straight pipe inside it, leaving it to look like a cat on the outside in case of visual inspection. To that I was told that the cutting/welding part would be difficult and need to be done by a professional welder. My thinking that a pipe inside would at least provide a straight exhaust path if nothing else.

What I didn't consider is ramming out the material and then sliding a pipe inside as you seem to be suggesting. I think that would be a more viable option.

chapstic951

I wouldn't be inserting a pipe after gutting it out. Doing so would reduce the overall diameter of the pipe and causing another restriction point right where I am trying to reduce it. If I could get someone to open the cat and insert a pipe, I would just have them remove the cat housing all together and risk the visual inspection. The garage I used does not lift the car off the ground to do a visual (that I am aware of) so I am not overly worried about it.

I am hearing that hollowing out the cat would cause a turbulance chamber due to the inconsistant size. Again, some have not problmes while others do. Theory says that it could cause problems. I will most likely leave the cat intact and focus my funds on a new 3" exhaust all around.

Tony951

I have an 88 951 that had the catalytic element bashed out - the car ran nicely! I cut out the old cat (which was an aftermarket) and welded in a straight pipe, as I didn't know the old cat had been 'modified', and the welds were poor since someone welded in the new 'modified' cat while on the car. I also cut out the tiny wastegate dump cat and welded in a straight pipe. I did notice a small performance difference with the straight pipe welded in - of course, I also cut out a restriction to the wastegate dump. It was mainly up high in the rpm range. I noticed that the wastegate is now more 'responsive' - it seems to bleed off boost easier, but not too pronounced.

One thing I learned the hard way: make sure you build a fixture or at the very least mark the pipe orientation prior to cutting, or fitting it back in will be a nightmare, or you will have interference with heat shields or the body. Remember - you have to connect to 3 different places. After my little learning experience, my muffler now hangs a bit crooked. I suspect that you may also break the studs at the downpipe, so I would purchase new studs and nuts as well as a stud puller if you plan to remove your cat pipe assembly...