free flow exhaust

[spieluhr]

hello. sometimes when i really push my car and then i come home and park it i smell rotten eggs which is a sign of a catalytic convertor gone bad. i hear you can just rip out the cat and put in a piece of straight piping to make it free flow. would this installation be possible, very difficult, or expensive? I also have been told that it owuld add some HP (Dont have any exact figures). And that if i did this i wouldnt pass my emissions testing here in Washington.

thanks

any information or opinions on this subject would be great!

[alanh]

other than it being illegal...yeah i think that would work

[BimmerE36]

It depends on the high-flow cat if it will be an easy install or not. If its a bolt on high-flow cat it shouldnt be that hard to do by youself, but if youre getting just s straight through test pipe some welding may be required.
As for emissions, if you get a testpipe you most likely fail. You would have better chances of passing with a high-flow cat.
With other breathing mods (ie cai, catback, tb) a new cat can help out with a few extra HP but nothing too noticeable.

[spieluhr]

is a high flow cat/catback an expensive investment?

[BimmerE36]

Highflow cats and catbacks are different. A catco high-flow cat would probably run you abuot 80 for the converter alone. Depending on the exhaust a catback (piping from the catalytic convertor back) can be expensive anywhere from 300-700.

[///M Power]

IT IS ILLEGAL!!!!!! you will never pass emissions, and it should be exptremely loud. i am not sure if the muffler does the mufflign of noise, or if its the cat converter, but when we drove my friends 240sx without a catalytic converter, and completely open headed, it SET OFF ALARMS BY JUST PARKING. also without the cat converter, it woul probably smell much worse!

[bitcore]

Originally posted by ///M Power@Feb 8 2004, 12:04 AM
i am not sure if the muffler does the mufflign of noise, or if its the cat converter,

That's the muffler's sole purpose, to muffle the loud pulses of air and turn them into as steady of a stream as possible. Racing mufflers sound slightly louder because they are designed to produce as little backpressure as possible. Cat's reduce the amount of pollutants that are released into the atmosphere. Also, because they introduce a disruption of flow into the exhaust system, they too also quiet down the pulses of air to some degree. Certainly not enough to not use a muffler at all.
Look at this link if you want to see inside of a cat and in-depth of what goes on.
Oh BTW, open exhaust smells worse than plain ol' sulfer IMO.

[Andrewsd1985]

You could take the cat off and hollow it out that way it would be like a straight pipe and would still look legit even if it didn't sound it.

[PhiLLaY]

hehehe i argee with andrews take ur cat out and get a metal pole and start jabbing it until its hollow > it wont increase the noise by much and plus your car will have a nice backfire sometimes when you downshift or hit the rev limiter, but its not good if you got a white car cause it stains the rear bumper. way better than a high flow cat ie more performance less cost compared to the same sized higher flow cat

[Furious]

just buy track pipes, they are larger in diameter i believe and well straight though

[eloff19]

my cat is going bad, it stinks even when i don't push it, and its been getting worse, how much money am i looking at to replace it? and does anybody have any recommendations on where to buy it or what to get?

[BimmerE36]

I would reccomend getting a catco or some other brand high-flow cat, they are legal, usually direct fit, and add a slight performance gain. Search google for one they shouldnt be that hard to find.

[eloff19]

thanks

[FruityOne]

i had straight pipes...i wouldnt do it again...it gets very loud...and second of all the fumes gave me headaches all the time...

[thekid]

well actually what state do you live in? In Arkansas for instance it is perfectly legal to take off your cat because there are no emmison testing. So depending on what state your from it may be legal.