high flow cat

i was wondering if i got a cheap high flow cat off ebay to go with my greddy sp2 cat-back if it would make it louder and throw and CEL?

Louder, perhaps. CEL, no.

What is a CEL??? Btw i was about to post a question about the hi flow cat off ebay. I was wondering is there is a benifit of gaining HP? I was thinking about buying a hi flow cat, but i just want to know is it worth it or should i jsut stick to me stock catalytic converter?

What is a CEL??? Btw i was about to post a question about the hi flow cat off ebay. I was wondering is there is a benifit of gaining HP? I was thinking about buying a hi flow cat, but i just want to know is it worth it or should i jsut stick to me stock catalytic converter?

CEL stands for Check Engine Light. Not sure about the hp gain from a high flow cat since I've only tried driving with the normal cat and a downpipe that eliminates the cat. Beware of those listings that say "high flow catalytic converter" on ebay when they're actually selling a test pipe. You won't be able to pass the smog test with a test pipe.

if it's turbo and your city don't smog ck, just lose it. I felt a big diff on the turbo.

if it's turbo and your city don't smog ck, just lose it. I felt a big diff on the turbo.

Or if they do, just keep your factory cat in the garage/shed. When you need to do an emissions test, take out your test pipe, put in the cat converter, pass the test, then reinstall your test pipe.

You'll throw a CEL unless your cat comes with a bung welded on for your stock rear o2 sensor, or you're creative. Welding resitors or wrapping in tin foil should also work. Some people don't get a CEL at all, whether or not any provision is made against it, but not most people.

It's federal law that your car have a cat, whether or not your state has an emissions test. This means you can get pulled over and cited for not having a cat. In lax states that's no worry. I live in NY state, and around here, while there isn't an emissions test, you'll get busted pretty heavy for running without a cat.

The addition of the HF cat will cut down on backpressure. The HP rise you see depends on your mods list. It's an easy, relatively cheap fix.

As silver98gst said, watch out for fake cats on E-Bay. This is a fake cat (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33629&item=7973357324&rd=1). Really, it's a resonator. Not only will you not pass emissions, you can still get ticketed.
This is a real cat (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33629&item=7973589911&rd=1). You should be able to pass emissions. It's CARB certified, so that holds true even in CA. Cops can't ticket you, either. Well, it's illegal to replace an operating cat, but I doubt anyone would be the wiser.

Have fun :)

What you can do is just take out your cat get a tourch heat it up and take a pice of metal and a hammer and fucking pound it out. Looks like you have a cat.

haha well i knew it was a test pipe. O is it better off for me getting a magna flow cat? or just that hi flow cat (test pipe)? i live in kansas so we dont have emmisions here. =)

If they had emmisions here about 60% of people would not be able to drive, encluding my friends with their 05 sti's.

haha well i knew it was a test pipe. O is it better off for me getting a magna flow cat? or just that hi flow cat (test pipe)? i live in kansas so we dont have emmisions here. =)



Well like i said, if your turbo then take it off, if your N/A then get a high flow cat.

Well like i said, if your turbo then take it off, if your N/A then get a high flow cat.


Ok then.. mine is a N/T so hi cat (strait pipe) from ebay it is! What about magna flow catalytic converter? which one is eventually the better in gain on a NT? Magna or hi flow cat??

Not to be a downer but we all have to live in this environment. You wouldn't just thow trash out your car window and you wouldn't dump your used oil and coolant down the storm drain so how bout pay an extra $10 or so on a high flow cat.

Not to be a downer but we all have to live in this environment. You wouldn't just thow trash out your car window and you wouldn't dump your used oil and coolant down the storm drain so how bout pay an extra $10 or so on a high flow cat.



So Magnaflow or cheap ebay hi flow cat??

Buy an e-bay magnaflow and weld flanges on for a total cost of 80 dollars.
<or>
Buy an e-bay resonator for 50 dollars.

So, if the environment and worries about getting curious cops is worth less than thirty dollars, buy the resonator.

Edit>> I don't see performance being very different between the two. The stright pipe offers a lil' less restriction. This is more a question of values, I think.

Buy an e-bay magnaflow and weld flanges on for a total cost of 80 dollars.
<or>
Buy an e-bay resonator for 50 dollars.

So, if the environment and worries about getting curious cops is worth less than thirty dollars, buy the resonator.

Edit>> I don't see performance being very different between the two. The stright pipe offers a lil' less restriction. This is more a question of values, I think.


ONE LAST QUESTION!!!!! loss of back end power with the resonator?

You won't lose exhaust velocity with a resonator, you'll gain it, same with the Magnaflow. Power throughout the range should improve, same with the Magnaflow. More-so with the resonator than the Magnaflow.

You won't lose exhaust velocity with a resonator, you'll gain it, same with the Magnaflow. Power throughout the range should improve, same with the Magnaflow. More-so with the resonator than the Magnaflow.


COOL! ok F with magnaflow. Resinator it is!!!

I was wondering if i should buy this? http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7974143859&category=33629&sspagename=WDVW

I bought a 2.25 resinator and also a 2.25 muffler and im going to do a 2.25 piping. So i was wondering if i should aslo get a 2.25 catalytic convertor as well? Or should i just replace that Catalytic Convertor and place that resinator in its place instead?? Just wondering before i do my piping because i want my cat to flow freely.

Get a cat! You will need it for emissions and you will be doing your part for the environment. ;)

That'll work fine. It's ODB II compliant and it doesn't matter for you whether or not it'll work with CARB (California). The diameter is correct, it'll fit with your custom setup and meet its needs. It's better for trees and birds and shit too, if you care about that sort of thing ;) Good luck.

That'll work fine. It's ODB II compliant and it doesn't matter for you whether or not it'll work with CARB (California). The diameter is correct, it'll fit with your custom setup and meet its needs. It's better for trees and birds and shit too, if you care about that sort of thing ;) Good luck.


Sooo... is that a Yes or a No? By the way we dont have emissions here so i dont need to worry about that. But i was just thinking performence wise and in the long run.

So me a yes or a no! hahaha

Buy the fuckin' thing :)

I bought a 2.25 resinator and also a 2.25 muffler and im going to do a 2.25 piping. So i was wondering if i should aslo get a 2.25 catalytic convertor as well? Or should i just replace that Catalytic Convertor and place that resinator in its place instead?? Just wondering before i do my piping because i want my cat to flow freely.

Is 2.25 the largest recommended piping you can safely run on a N/T?
and would it be fine to run a stait pipe from the headers to muffler on a N/T?

Is 2.25 the largest recommended piping you can safely run on a N/T?
and would it be fine to run a stait pipe from the headers to muffler on a N/T?


Well 2.25 is the biggest i would go with scince i have no turbo. 2.5 is ok but i want my piping to match all the 2.25 all the way... so 2.25 outlet on the headers all the way thru. But running a strait pipe would make your car flow more easier... but i heard if you go that way you gain a bit more then without a catalytic converter. So i guess im going to be going with the 2.25 catalytic converter =\

Will a Magnaflow Cat/high flow increase the noise at all compared to the stock one?

Will a Magnaflow Cat/high flow increase the noise at all compared to the stock one?

This was answered on the first page, second post. The answer was "perhaps."

Well, I guess I can try to be a little less vague :) Its less of a restriction than a stock cat, so it should be louder. But its not a whole lot less restrictive, so its not a whole lot louder. But there should be some sound level increase, wether you can percieve it or not. Going from a cat of either type to a test pipe will of course add to the noise level in a much more noticeable manner ;)

I dont think i would woudnt want my car to be too loud. I know it will get anoying later on and specially if you want a sound system. But what i do want is that deep mean sound to my car... not those ugly high pitched sound. Too bad my car cant sound like a sooped up 95' or so Mustang.. now that car sounds hella mean when its fixed up.