Catalytic Converter, legalities Options

[Red_06_EvoRS]

I've been hearing ugly rattle/vibrations since the summer on my 93 GSX. I got out and listened and it sounded like it was coming from the catalytic converter area. It only does it when idling slow or chugging from a dead stop. I finally took it to a local shop and they said that I need a new catalytic converter (a couple of heat shields could also use some work).

I've always had in the back of my mind possibly putting on a larger exhaust, etc. etc. I know replacing the catalytic converter for no good reason is supposed to be illegal. So my question is, if I'm going to have to replace it anyway, is it legal to put in a larger/higher flowing one? Or does the stock one do the job well enough not to worry about it? I could see where the feds might say that if it's not replaced with an exact replica that it's not guaranteed to handle the smog duties that it's meant for. Anyone know?

[SCCA Stang]

if I'm going to have to replace it anyway, is it legal to put in a larger/higher flowing one?

If your heart is dead set on using one anyway, I have a slightly used high flow laying around (less than 5,000 mi), I will sell it to you if you wish, make an offer, new it is worth $100 or more.
it is a 2.5" inlet and 2.5" outlet

the only cars that you have to worry about are the cars made from '96 and up because of the OBD II system, you will get a check engine light with out one, and you will suffer gas mileage and possably performance due to screwy air/fuel ratio readings

[Rollout]

isnt there a kit u can get that can remove the cat on the 96 and latter without messing up the engine light, mpg, etc...
removing the sensors or somthing?

[SCCA Stang]

isnt there a kit u can get that can remove the cat on the 96 and latter without messing up the engine light, mpg, etc...
removing the sensors or somthing?

yes, but on such a low displacement engine, a 2.5" or larger high flow cat flows well enough that,(in my opinion) it isn't worth the money spent for the devices that "trick the computer"

If you want to go that route, I think that Jegs and Summit sell them

[natedogg]

the only cars that you have to worry about are the cars made from '96 and up because of the OBD II system, you will get a check engine light with out one, and you will suffer gas mileage and possably performance due to screwy air/fuel ratio readings

The rear O2 sensor is there only to trigger the CEL if the cat is plugged or burned up. It has nothing to do with ECU calculations on fuel and timing tables. That's what the O2 sensor after the turbine is for. Your gas mileage and performance will not change, but the CEL will be on all the time and that can get annoying. Plus you'll never know if there is some other problem that would trigger it otherwise because its always on anyway.

BTW, the cat issue has become pretty sensitive in the past few months. The more popular DSM tuning companies aren't even allowed to advertise straight pipes on their websites anymore because the EPA is cracking down on them. Dave Buschur wrote some posts about this on the evo boards a month or two ago. They're watching...

[Rollout]

I was just planning on buying an apexi n1 downpipe which eliminates the cat altogether... this shouldnt be a problem should it?

[AWD DSM 1]

I see what you're saying Nate... If you aren't into breaking federal laws like a lot of us, a high flow cat is a good way to go. If you are planning on putting an exhaust on in the future, I'd wait and do it all at once (or do it now if you can!). If you were to bolt a 2.5" cat in now, and then upgrade to 3" pipe later, then you'd have to buy anther cat (which technically woud be illegal).

Honestly, I've concidered putting one on, just for the sound deadening properties, not necessarily the emmisions side of it. I think for now I'll try it without.

[Red_06_EvoRS]

I took my car into Meineke (in Bloomington) for a second opinion this morning. I've had good luck with them in the past and I figured it can't hurt plus they always let you go out into the shop and actually see what they're talking about with it up on the lift.

They said that it was just the heat shields as I had always suspected. They took them off and charged me $5. The rattles are now gone.

Neil Tire & Auto was going to charge me over $300 for the cat & heat shields. The thing is I've not had a problem with them in the past with tires.

[SCCA Stang]

I took my car into Meineke (in Bloomington) for a second opinion this morning. I've had good luck with them in the past and I figured it can't hurt plus they always let you go out into the shop and actually see what they're talking about with it up on the lift.

They said that it was just the heat shields as I had always suspected. They took them off and charged me $5. The rattles are now gone.

the best thing is that you find a shop that you like, that treats you righjt and doesn't like to rip you off, honest shops are sometimes hard to find but they are out there, find one and stick with em...