Unless you have a high output engine (ie turbo/supercharged), is there really any reason to go a 100cpi cat over a 200? The extra flow won't turn into much extra power (if any at all), and your emissions will more than likely be over the limit of what it should be for your car....

Cheers

ToranaGuy

Because they flow better and you are unlikely to ever get emission tested...

The OP's sig states they have a mild engine with 130rwkw, doesn't really need it & the extra expense does it? Doesn't need the risk of getting EPA'd & the fine that comes with non compliance either.

Cheers

ToranaGuy

seeing as the law in nsw, (at least last time i checked, also not sure how it stands to the other states) is ANY modification to the standard cat is considered illegal i just went with a 100cpi, it does smell a little bit, but not noticeable, you really have to have the car in the garage and be standing right behind it to notice the smell. so im gonna recommend a 100cpi

I doubt the cost would be any different.

Less restriction is always good.

Whats the point of modifying if you waste your time plugging up the exhaust when you don't have to?

Have you ever met anyone who has been substantially fined for not meeting emissions?

I run the venom cats on my Fairlane when I had it and they were great.
I am also running Venom cats on the XR8 now. Cannot fault them for the money.
While yes 100 cell isnt legal to the EPA the law in NSW is you must have a functional cat convertor if you car is 86 or newer. It doesnt say anywhere how well it has to work it just has to be functional.
As far as the EPA goes changing a cam is just as illegal as running a 100 cell cat. A cat wont clean everything up and if you go with a bigger cam it hasnt been tested and proven to comply with ADR's which is where the EPA gets you. Tuning a factory ECU with a J3 is the same story.
If the EPA want to do you they will one way or the other. I highly doubt many members cars on here are under the 90db required to pass the EPA either.
If you knock the guts out of a cat there is no excuse you could use and you will get raped if they ever checked it. Running a 100 cell you can plead ignorance and just get a notice to change it. Providing the cat is functional you should be fine.

how would they konw of you hav either knocked the guts outta the cat or just got a seriously high flow one?

Smell of the exhaust? Then a gas test.....

My mighty boy is 1986 built, but DOES NOT require a cat under the rules of ADR27a, not all post 1986 car's do! It's a commercial vehicle under 850cc which is exempt from a cat. Last roadworthy the place tried to fail me due to no cat, till I pulled the book out & shown him why it doesn't have one, it's not required & never has had one. The exhaust smells distinctly different to a car with a functional cat.

I guess if a 100cpi doesn't cost any more, and you can plead ignorance as you still have a cat fit, then why not? As for the noise being over 90db, I'm a little , but only a tad. Not enough that you can pick by ear....

Cheers

ToranaGuy

i remember you telling me that Jay. and i believe commercials didn't need cats til 1991 or something.

i just did the highest flow so i could squeeze as much power out of a N/A 6 i could on a budget

Very little and i mean very little gain going 100cpi and by most cases they sound tiny so i went 200cpi and very happy

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Spot on

The big issue is with knocked out cats, as long as you have a functioning catalytic converter then you are ok from a roadworthy perspective. EPA on the other hand is completely different, and while the cat may be compliant (200cpsi or 400cpsi) like EVL098 said, it does depend on other modifications you have done, cam, tune etc as these will all change the emissions output.

The smell is a tell tale sign of decat (and a 100CPSI but not as bad). The 200CPSI is much cleaner.

Most tend to go for a 100CPSI as it is higher flowing and does give a little more volume than an equivalent 200cpsi. Whether that translates to more power though depends on your application, on an NA 6 the flow difference will result in a negligible gain, the difference is greater for a Supercharged/Turbo (especially Turbo) car. The DOHC motors though can sound a little raspy/tinny with a 100 but that is a trait associated with a lot of DOHC 6s and 4 cylinder vehicles when you open the exhaust up, muffler choice in this area helps immensely.

Also most 100CPSI cats will only be Euro 2 compliant. You can put a Euro 3,4,5 or even 6 coating on it but at the end of the day the substrate just doesnt have the density to be able to filter the gases effectively (unless it has a ridiculously long body).

The balance is between emissions and flow. If you are concerned about emissions the 200CPSI cats are great and offer the best balance between flow and filtering and on most applications will work perfect. Especially on a V8 running 2 cats as the exhaust flow is split, although the 100s do sound better on the 8s haha

We also have the 400CPSI cats and they all have a Euro 3 coating and are legal on newer model cars.

If anyone has any concerns or queries just drop me a msg, more than happy to help