Prior owner removed cat

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The prior owner removed the cat on my 97 I bought last week. The car seems to run fine, is there any problems besides throwing a cat code I should be really worried about? There are no emission testing in my state as of yet.

Also, can I install another muffler where the cat was to quiet it down some?
Thanks!

[cooljess76]

Removing the cat on a daily driven car is a really sh!tty thing to do. I mean, I could understand if it were a track car, but just because your state doesn't participate in emissions testing doesn't make it right. I'd try to track down a used cat(it's illegal for junkyards to sell them) on ebay or one of these forums, or bite the bullet and spend the cash at the dealer. Ask the previous owner if he happened to keep the old cat. If you bought it from a dealer, make them replace it with a brand new one or threaten to report them to the EPA. BTW, most aftermarket cats(with exception of a few) won't work on OBDII BMW's as they usually fail within a month or two. Stick with OEM.

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Well I dont want to fork out $600 for a cat on a car worth 4g. What afermarket brand do you trust?

[cooljess76]

I'm not sure on the different brands, but I do know that theres different types of cats. Unfortunately, our cars are very sensitive and reject the cheaper cats. Some of the cheaper cats have a ceramic core while others have a metallic core. The core is the honeycomb element inside of the shell which is called a monolith. The monolith heats up to extreme temperatures and attracts the unburned hydrocarbons causing them to stick to it and burn off before being expelled into the atmosphere. Ceramic core cats don't work as efficiently and commonly fail when installed on BMW's. Metallic core cats are somewhat better, but don't always work either. BMW OEM cats have monoliths that are specially coated or impregnated with precious metals such as platinum that attract the hydrocarbons more effectively. This is why they are significantly more expensive. Now when you're shopping for an aftermarket cat, you'll come across two different types. Direct fit, which basically has been welded to a section of pipe and fitted with flanges that bolt right up to a specific model of car, and universal fit which is basically sold according to engine size and have to be welded onto your car at a muffler shop or whatever. Just because a cat is a direct fit and was designed to replace your OEM cat doesn't always mean that it will work. All it means is that someone is making a little extra money by copying the dimensions of a particular car manufactuers catalytic converter and making it easier by offering a bolt on application. Universal cats don't always work either, so they're not actually universal for all cars. Most universal cats aren't made to the standards that BMW uses and won't perform the same. There's also a such thing as a highflow cat which is pretty much useless for our cars. They don't work nearly as effectively and are designed to reduce airflow restrictions caused by the stock cats and actually require a slight level of backpressure to maintain low end torque. That's pretty much all I know, hope it helps, who knows maybe you'll notice an improvement if you install one, but more importantly you'll get rid of the CEL and help the environment by reducing emissions.

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Great, thanks for your help!

[cooljess76]

Here's a couple that I would look into:

direct fit

universal

I'd be sure to get a warranty and some type of guarantee that it'll work.

[aceyx]

I would trust this guy's advice:
http://www.ultimategarage.com/catalyst.html

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Thats alot better price than I have found, thanks!

[Keach]

Don't waste your money and time on an aftermarket cat for your 318ti. I replaced my cat with a CATCO replacement brand cat and it still tripped my OBDII cat code. I've had about 6 different aftermarket units on my car and all of them end up tripping the code sooner or later. Most last about 250-500miles before the codes cycle and the check engine light comes on. Universal applications won't work on our cars because the factory cat has a side inlet for the exhaust pipe, so unless your really good at bending and weilding pipe it's not going to work. Not to mention i doubt the "universal" cat will work anyway because essentially that is what is on the direct fit aftermarket cat (they just take a universal cat and bend/weild pipe to fit it). Another problem with the aftermarket cats is that they almost always cause an annoying exhaust rattle because none of them fit exactly right. It is really ****ty to drive a car with no cat, but I still wouldnt spend the money and go through what ive been going through for the last year, when emissions arent regulated in your area. Im still dealing with this problem cause i dont want to have to shell out the 2k for an OEM when my car is only worth about 4k.

[aceyx]

Which brands have you tried?

[Keach]

CATCO and DEC, they look just about identical. Unless someone personally tells you that the aftermarket brand has worked for them, I would avoid all aftermarket cats. If you find out of one that actually works for you let me know cause im still in a real bad situation with mine, as emissions are regulated in my area.

[Keach]

Originally Posted by cooljess76

Here's a couple that I would look into:

direct fit

universal

I'd be sure to get a warranty and some type of guarantee that it'll work.

The warranty and guarantee won't take care of the cost to ship the unit back to autoparts warehouse or the labor of having someone do the work for you. Don't waste your time with CATCO or DEC cause you have to pay to ship it back to them. TRUST ME, I HAVE PERSONALLY GONE THROUGH ALL OF THIS AND IT SUCKS!!! They made a huge hassell for me to get my money back after the second one didnt work so i spent 60 dollars, 30 to ship each of them back to the company.

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Well i put about 3000 miles on with no cat with no problems. Besides the code and the louder noise/slower at low rpms. Im getting 27.6 mpg, and the car runs great. And I have alot more power at interstate speeds than my prior 318 I owned. And for the tree huggers, my 318ti with no cat still lets off about the same emmisions as a mid sized truck.. I think Im just going to leave well enough alone.

If BMW didnt have such a poor design on factory cats this wouldnt be a issue.