Catalytic Converter Diameter Question

['00CamaroV6]

Ok, so I want to work on my exhaust system a bit. I'm planning on buying a new cat-back system, more specifically the Flowmaster system for my car. While I'm down there I also wanted to switch out my catalytic converter. I know that the stock cat is 3" in and 2.25" out, and my new exhaust will be 2.5". What size cat should I buy, 3" or 2.5", does it matter? Either way I will need a reducer, but I don't know if the size will effect backpressure or cause bottlenecks or the like. Which size cat do you all think would be better in terms of performance, sound, etc.? Thanks in advance.

[FunkZ]

If you're buying a 2½" cat-back, get the 2½" cat. If you're getting the 3" cat-back, get the 3" cat.

['00CamaroV6]

That makes sense, thanks. While I'm at it, does anyone have a recommendation on a new cat? I've been hearing a lot about catco and carsound and the like, any preferences or experiences?

[FunkZ]

I've had the Carsound on for about a year and a half now, no problems at all. I got it from the same dealer with my Magnaflow cat-back. I am not required to pass a sniff test however, only a visual inspection at this point.

I have heard of some people having problems with the comb breaking up in their relatively new Catco's, but others go for years without problems.

[98Camaro3.8]

Originally posted by FunkZ:
I have heard of some people having problems with the comb breaking up in their relatively new Catco's, but others go for years without problems.

You hear those rumors all the time, but only actually read of it happening a couple times over the past 3 or 4 years. Most of it is just rumors of problems. I personally don't know of anyone that had a Catco go bad, besides the heat shield.

[FunkZ]

Like I said, I read posts from some (how many? 3, 4, 5?) people that had a problem with their Catco cat. I'm sure the posts are still here if someone were to search for it. I'll agree that that few doesn't necessarily mean Catco has a problem with their cats, and 2 people with a problem gets repeated and repeated so many times all of a sudden it's a huge issue... but then I can't recall anyone ever complaining about their Carsound cat going bad. Heh, maybe my eyes are just partial though. :D

['00CamaroV6]

Thanks for the input guys.

I was looking up the two brands of cats on eBay and there is a lot of talk about O2 sensors and O2 bungs. Will I need to buy these or are they already on my car now to reuse? Thanks.

And the air tubes, but I think I read somewhere that those are only necessary in California?

[evangelion137]

you're going to need the O2 bung to mount your O2 sensor (drilling a hole and welding is required). Or you can get an O2 simulator and just forget about the O2 sensor (no drilling or welding required).

..i don't think you can really reuse the bung on there already, if you could it would be more work and more of a hassle to reuse it.

[FunkZ]

AFAIK there are no AIR tubes on 4th Gen cats (there was not on mine) however you may have a pre- or post-cat O2. You could reuse your existing O2 but you will need the bung welded in unless it is currently in the intermediate pipe, not the converter. Or you can get an O2 simulator.

['00CamaroV6]

If I had a garage do my install they would have bungs right? I wouldn't need to order it off the internet? It seems like a pretty simple part. And yeah I want to go out and look at my car but it's kinda cold, how would I know what to look for when looking for the O2 sensor?

[ezrollin]

98, what do we need a heatshield for?
how can a heatshield go bad?
i was gonna rip mine off

[FunkZ]

Heh, yeah I think he was saying that seemed to be the only common fault, which isn't a big deal.

Yeah, I would expect a good exhaust shop to be able to modify the thing to work with your existing O2's. What do they look like? Well, just look for the electrical wires coming out of your exhaust.

['00CamaroV6]

Ok thanks for all the info. Does anyone else have any thoughts on the two cats? I'm still looking around for info on them.

[98Silver6]

I had Carsound for about year and a comb broke the damn thing rattle like hell so im going with catco now, also i want to make sure before i order do our cars take 14' or 16' cats cause im too lazy to measure under my car?

[articacid]

you should go with a 3 in cat no matter what. you better off having a bigger cat then a reducer than reducer then a smaller cat.

stock cat is 3 inches with a reducer basicly.

[ November 08, 2005, 09:50 PM: Message edited by: articacid ]