High Flow cat question

[ZigsGSX97]

I have a Greddy SP exhaust on my car with a custom downpipe (2.5"), and i want to get a high flow cat. What kind of performance am i looking at? Is it a big difference? Will it matter at all?

 

[phatTSi]

Just get a test pipe they are cheaper and better for performance. You live in illinion and if they are anything like iowa they dont check for that kinda stuff. Its basically for California.

 

[ZigsGSX97]

In Illinois they do

 

[Nabyar]

Well, you're looking at $20 for a test pipe, which has no restriction AT ALL or $60-70+ dollars for a highflow cat which still has a tiny bit of restriction.

 

[FearceDSM]

If you do not care about the being legal then run a test pipe. You can always get a test pipe for the track and run a high flow cat the rest of the time. I run a 3 inch hi flow cat and I have no compalints and I stay legal. You can still put up good numbers with a high flow cat in place. But make no mistake, there is a slight loss in hp with a cat. Depends on what is more important to you. Good luck.

 

[coltboostin]

Test Pipe

 

[NewB2dsm]

You guys saying no cat, have not ran a good highflow cat.

I have a car sound 3" highflow cat i use when i feel like it. I ran a 12.9@107mph with it in place on my small 16g at 20psi on pump gas. WIth a highflow cat you do not loose as much as what people seem to think. I cant tell when the cat is in or out, i can only tell b/c the exhuast tone changes. If i could id run the cat all the time, but race gas does bad things to mr.cat

 

[STECARS]

^^^ what cat do you have ?????? I also prefer to use a cat for emissions (eventhough all other emissions are removed) But , i want to run a cat to also quit up the sound.

 

[NewB2dsm]

^^^ what cat do you have ?????? I also prefer to use a cat for emissions (eventhough all other emissions are removed) But , i want to run a cat to also quit up the sound.

Its called "car sound" I passed emisstions here in st.louis with it.

 

[eclipse420a2nr]

you could use a random technology cat. they olny have about 1 hp @ the wheels restriction compared to running a pipe straight through and there smog legal but they're pretty expensive.

 

[4geze63]

what does the obstruction look like in a highflow cat vs. a stock cat?

 

[coltboostin]

You cant say it has a 1hp @ the wheels restriction, that may be true for the car that they tested, but not for everyone else's settup. What turbo and exaust was this on, at what psi, with what mods....

You dont know, and their is a 99.99% chance your settup is not the same, so the results wont be the same.

Wether or not I have used a high flow cat would not change my opinion of them. It is a restricion, no matter how high flow it is, Race gas will destroy it, and most of all, it is a hell of a lot cheaper to slap on a test pipe.

 

[NewB2dsm]

You cant say it has a 1hp @ the wheels restriction, that may be true for the car that they tested, but not for everyone else's settup. What turbo and exaust was this on, at what psi, with what mods....

You dont know, and their is a 99.99% chance your settup is not the same, so the results wont be the same.

Wether or not I have used a high flow cat would not change my opinion of them. It is a restricion, no matter how high flow it is, Race gas will destroy it, and most of all, it is a hell of a lot cheaper to slap on a test pipe.

your missing the point, if you want a car to be legal then you have to have a cat. If he wants to pass emissions and still get the best proformace he can then a highflow is a must.

I have one just to be on the safe side, so if i even need to do anthing like that i have one. And its not too hard to swap out 4 bolts and a pipe for a race night were leaded gas would be ran.

 

[coltboostin]

I have a Greddy SP exhaust on my car with a custom downpipe (2.5"), and i want to get a high flow cat. What kind of performance am i looking at? Is it a big difference? Will it matter at all?

He did not ask anywhere in this post for "emissions" or being "legal". The only thing I see here is performance, and the unit in question that will have the best performance will be a test pipe. If he said he wanted to pass emitions and spend a load of money, I would have told him to get a high flow cat.

A proper test pipe will temporarliy replace the cat, so when you need to , you can just throw the cat back on. So either way, emissions is not a worry.


Test Pipe

 

[NewB2dsm]

He did not ask anywhere in this post for "emissions" or being "legal". The only thing I see here is performance, and the unit in question that will have the best performance will be a test pipe. If he said he wanted to pass emitions and spend a load of money, I would have told him to get a high flow cat.

A proper test pipe will temporarliy replace the cat, so when you need to , you can just throw the cat back on. So either way, emissions is not a worry.


Test Pipe

try to put a stock cat into a 3" system. If it works tell me.. oh yea it wont.

and not to be an ass, but read the thread man. We will use your quote on me then the 2nd and 3rd reply.

Just get a test pipe they are cheaper and better for performance. You live in illinion and if they are anything like iowa they dont check for that kinda stuff. Its basically for California.

and he replies with...

In Illinois they do

BAM, he wants the car legal. b/c in IL they seem to check for a cat.

I also reponded to anothers question about my cat, which i thought was the thread starter but was not. Either way the thread starter obviouly wants the car somewhat legal, so the testpipe is out. Also he is asking what will a highflow cat do over a normal cat. not is a test pipe better.

 

[Just Nasty]

Ok, from what I have read some high flow cats are still illegal and for off road use only.But their not really that expensive, you can pick some up for around 80 and they claim a 10-15 HP gain over the stock cat, most other high flows probably cost around 120 though.

 

[coltboostin]

Please explain how a stock cat on a 3inch exaust wont "work"? I know at least 6 DSM's in the area alone that run absolutly fine this way when they go to get e-check.

So your telling me since he said they check for cats WHEN HE GOES TO E-CHECK in Illinos thats he wants to have a cat all the time? I would like to know where you got that assumption from, since he never stated that.

They check for cats when you get e-check in Ohio.

Wait, does that mean I want a cat on my car 24/7? No.

On the 80$ not being expensive, to some it is. When your a college student, or high school, makeing blah blah blah.... You have heard the story a million times, 80$ for a converter that is already on your exaust is not nesesarry, IMO. If you have minor mechanic skills, you can make a slip fit test pipe and be good to go for the street and have the cat for echeck.

 

[Just Nasty]

On the 80$ not being expensive, to some it is. When your a college student, or high school, makeing blah blah blah.... You have heard the story a million times, 80$ for a converter that is already on your exaust is not nesesarry, IMO. If you have minor mechanic skills, you can make a slip fit test pipe and be good to go for the street and have the cat for echeck.

I hear ya, probably the only time you'll want a cat or atleast a high flow cat over a test pipe is if a cop pulls you over and checks your setup if he suspects you are running an illegal exhaust.I've never seen it happen, but I know it can.Yet, just out of curiosity how much are we polluting by running with no cat?

 

[NewB2dsm]

Please explain how a stock cat on a 3inch exaust wont "work"? I know at least 6 DSM's in the area alone that run absolutly fine this way when they go to get e-check.

So your telling me since he said they check for cats WHEN HE GOES TO E-CHECK in Illinos thats he wants to have a cat all the time? I would like to know where you got that assumption from, since he never stated that.

They check for cats when you get e-check in Ohio.

Wait, does that mean I want a cat on my car 24/7? No.

On the 80$ not being expensive, to some it is. When your a college student, or high school, makeing blah blah blah.... You have heard the story a million times, 80$ for a converter that is already on your exaust is not nesesarry, IMO. If you have minor mechanic skills, you can make a slip fit test pipe and be good to go for the street and have the cat for echeck.

Ok explain to me how a stock cat that WILL bolt to a 2.5" exhuast will bolt to a true 3" exhuast. I know my stock cat wont bolt to my 3" piping. Maybe im the wrong one here, but last time i checked when a cat bolts up to a 2.5" pipe it wont bolt to a 3" pipe without some kind of reducer on your exhaust or cat. So in other words, a true 3" setup wont work, unless you modfiy the cat.

Also im not saying he will run a highflow alll the time. But he thought about being legal. I run a test pipe alot of the time, but i also like the fact that i can be 100% legal in a matter of a half hour. And still make 12 second pass's

also im a broke college student.

 

[coltboostin]

All you need is a reducer, and weld the reducers onto the stock cat. Their you have it, slip fit stock cat. FI you want to be rediculous about it I can try to get pics of it up, but I dont have a digital camera, so it is a pain.

 

[telly699]

Whats the point of having a 3" exhaust that reduces at the cat to 2.5"? Doesnt that negate any advatages of the 3"? Or your saying slap the old cat on just for emissions?

 

[coltboostin]

Yes.

It is only used for emissions time. Their is no point to any cat anyways

 

[FrankNstein]

Most all 3" pipes/cats will neck down to accommodate a flange. I opted not to use the flange on my 3" downpipe and bolted up a 3" Catco high flow universal fit ($41 shipped). I hacked off the flange on my 3" catback, and connected it all with an extra 8" pipe and band clamps. You can see light through the cat, legal, flows well, but is damn loud around town.

 

[1LE]

They check for cats when you get e-check in Ohio.

Wait, does that mean I want a cat on my car 24/7? No.

They don't have e-check where I'm at in Ohio, but they DO have random roadside inspections... You don't want to be driving around without a cat!

 

[coltboostin]

Random inspections? That is absloutly retarted. They have real crimes to fight here in Cleveland!