M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => General Topics => Topic started by: joelthejedi on February 22, 2010, 09:19:03 AM
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Since I got my car, it has sounded like a crushed up tin can was rattling around in the Cat under moderate to heavy acceleration. I always assumed it wouldn't be a problem, but I was reading today about it could be clogged and causing power/mileage loss. I also don't like the noise (it isn't terrible.. but it doesn't sound good at all)
Also, until my new ignition coils come in the mail this week, my car will be missing on one cylinder (one coil failed). Apparently running all of this fuel through the cat can damage it further.
Point is, whether it was already destroyed (it rattled), or this week's driving destroys it, I think I'd like to do something about it. I've been getting kindof poor mileage (18-20) and I am trying to go after it. Hopefully the new ignition system will help smooth things out, but maybe a new cat would help?
What is involved with replacing the cat? Can it be done at home? We have an arc welder and an acetylene torch. Can you buy something like this: http://www.amazon.com/MagnaFlow-94005-Universal-Catalytic-Converter/dp/B000COVG8E/ and just slide it on and weld? I'm not sure at all - but I just want whatever solution can get rid of my current cat.
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I have the same rattling. I thought it might be a heat shield, but it isn't. I'd figure the cat is just cut-and-weld. I've heard good things about the Magnaflow, just not sure what fits.
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do your self and get a stainless steel ceramic core cat from vibrant performance. they are heavy wall tig welded and spun stainless steel. the case looks to be about the thickness of scd 40 stainless. worth ever penny. they flow great.
http://vibrantperformance.com/catalog/product_info.php?cPath=1022_1035_1063_1112&products_id=848
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I've had the honeycomb material bust loose in the cat and it's horribly annoying. Here is the problem when it breaks loose. That material can ignite. Don't ask how I know. It makes no sense, because you'll wonder why it won't ignite under normal circumstances. I don't have the answer to that. But seriously, a busted cat can be bad news. Just hollow it out.
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I put on of those magnaflow universals on and it seems to be working great! No more stink and I didn't notice any performance loss at all. I had it welded on at a muffler shop. They did look at me funny for wanting to add a cat though. Our state has ZERO emission laws or inspections etc. At least nothing is enforced if there is a law.
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Thanks for the help! I'm thinking about the Vibrant Performance cat posted by 4banger. Could someone who has changed a cat tell me what is involved? It looks like the current one has the inlet on the passenger side, and the outlet on the driver side - but universal ones are straight through... how do you install it? Do you need a pipe with a bend in it?
I'm fine with welding and cutting and all that.. but I'm less confident about being able to get a hold of the proper 2 1/4" pipe to fit the application. What is involved, guys?
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there is a cross over right before the diff. the one i linked is the correct size for stock piping. curt the old one out and put your new one in. id use band clamps. it be a bitch to weld it up on the car.
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when the honeycomb stuff breaks loose in your cat it can rattle around until it's sideways, so that your exhaust flow is forced around it instead of through it.. like a banana in your tailpipe. I found a cat in this state in a Ford van one time, and it was perpetually overheating. also, combustion mixture in a cylinder that is not being ignited will wash the oil from the cylinder walls causing rapid wear of rings and bore.
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i have a 3" in/out magnaflow cat in storage awaiting my turbo install. looks like a really nice piece, you can see straight through it.
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like a banana in your tailpipe.
(http://farm2.static.flickr.com/1171/530679899_5c89902e55.jpg)
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hah!