so im going to be installing a full exaust and header but i have heard mixed things about running a cat or not running one. the car is a 93 hatch running a jdm d15 b with matching 5 speed. the motor is bone stock. so should i run one if so why?
should i not run one why?

 

i wouldnt run one cause without it it sounds better and i do believe that u get a hp gain too but that depends on what exhaust u r going to be running

 

exaust not sure of bought it off craigslist it has no markings at all. ive been told you wiil loose torqe and i dont want that.

 

exhaust would prolly sound the same without it.
use a resonator.
a cat is only for emissions purpose. resonator is for the noise.
sum states require it.
if not. ditch it. its a power limiter. they suck

 

ya i have no emmissions at all were i live. only thing is the exaust shop will not touch my header cause it has a flex pipe were the cat is suppose to be. some law and regulation.also the header has some weird *** flange that needs to be cut off and matched to the exaust..

 

buy a welder
or makes friends with a welder and go to town with it.
3" straight pipe all the way back to a fake muffler.

you can always buy premade or custom order from ASP or kteller. a bit of $ but they do stainless steel or full aluminun exhaust any size with nice mufflers.

 

bump

 

To not run a cat, regardless of emissions or not is illegal in the U.S.A. If a cop has reason to look under your car and not see your cat, you will be **** deep in car trouble. Don't take it to a muffler shop if you aren't like good *** friends with the owner because they won't touch it, it's illegal for them to mod a car against car regulations obviously.

A cat hold a little bit of pressure to the exhaust system but not much really. It is of course more for emissions but there will be a sound change, might not be a large change either though. Going with a straight pipe will give you more low end power where as running a hi flow cat will push some of that more to the high end. Also depends if you run a 4-2-1 header or 4-1. You'll also need to spend money on a CEL eliminator to fix the CEL issue with the o2. Really, I don't see much benefit. Much easier to just leave it because UNLESS YOU'RE BOOSTING, you'll see minimal gains, sound change, wasted money and potential legal issues, all on a D series.

*But you can also buy straight pipes that look like cat's but just go straight through. Still, not worth it.

 

Couldn't have said it better myself.

 

very well said thanks .

 

your car has less than 200whp... just keep the cat... it will sound better and perform better in your lower powerband...

 

And we'll all breathe a little easier.

 

very true lol

 

Running without a cat you'll also smell exhaust in the car all the time. The difference between a test pipe and a stock cat is a whopping 2whp.

 

Lol don't encourage people like that...2whp just gets some people excited lol...I mean come on...people buy throttle body spacers and e-turbos for 50+ dollars...

 

i don't smell it all the time... mostly when backing up or sitting still for a long red light with the windows open.. but yeah, it stinks badly.

i don't entirely dislike the sound.. but it is noticeably raspier esp. in the 3000-4000rpm range.

OP: run it with a cat. any "drawback" to running one can be negated by installing/designing a proper system around it (good header/manifold, quality mid-pipe, good axle-back) my only excuse for running without is curiosity... followed by laziness in getting one back on.