Gut The Cat.....yay Or Nay....hahahaha

[3000Star]

i want to know everyones oppinion of gutting there cat .....weather thats the only thing youve done to your car or its one of hundreds...everyone give me your oppinion....cus im doing it next weekend weather folks like it or not

[Jag1718]

Does gutting it cause any problems with emission testing? Cuzz if it doesn't and it gives better flow or something...I'm probably gonna gut them unless someone has good reasons not to.

[Musashi3000GT]

Nay.
1. the catalytic converter is precisely engineered so that the flow of air passes smoothly and trapps all harmfull gasses. they key word here is "smoothly", yes it is restricted but it does have a precise flow. by gutting it you cause a flux or vortex in air flow within the cat.
2. it does affect emission testing and will cause you to fail the test.
3. its kinda pointless to gut it because due to the windwhirl effect you only gain about 2-3 hp as opposed to the race-pipe swap which can give you up to 9 hp gains.

[renesis13t]

gut the cat that would be a waste of a cat unless it was clogged and no good just go to your local muffler shop and have them make you a mid pipe to put in its place something you can bolt right up probally only cost you 60 bucks and a must if you plan on runing high boost

[Igovert500]

Go on ebay, or another site that was listed a week or so ago...you can find a replacement 3" test/race pipe to just bolt on instead(for under $30)...then when emissions comes around, just bolt the cat back on.

It's cheap, less time consuming, less of a PITA(the cat material gets all over your clothes, hair, eyes, everything).
If you really want to gut something, gut the precats, they are more of a restriction then the regular cat. Plus they are only needed when the car hasn't heated up enough for the main cat to be effective...so you can still pass emissions with gutted-precats (excluding Cali) if you drive the car hard for an hour or so before the emissions testing.

[3000Star]

well in NC they dont test emissions on anything 95 or lower they just check to make sure that you have a cat. and a question i have is when you gut the cat or either the precat ..does either one give you a different sound..or do you just have to get the racing pipe for better sound. cus i wanna make her scream

[Igovert500]

It will make it a bit louder...any freeing up of exhaust will change the tone a bit.

[Jag1718]

Ok, so gutting ur cats is bad...but the pre-cats is good? As long as i can still pass emissions i'll be happy. However, I'm looking for an exhaust sound like the vr4 on the video with the porshe 911 turbo. That exhaust was just great...it wasn't super loud and it sound nice and deep. With that said, borla will do it?

[Thourun]

I like borla, it's what I plan on getting for the VR4 in my future even though it dosent realy increase preformance by much (just the ricer in me I guess lol). Too bad they don't have clips of their exhausts to promote them and spur compitition among brand names.

[Knight2040]

3SX.com has a sound clip of the bolra under the turbo exuasts.

[The1NamedMarc]

gut the pre-cats and get a test-pipe.

[Hotshot8792]

removing any restriction from your exhaust will free up power. If you own a TT, and you can get rid of your cat, then do it because getting rid of your cat will lessen backpressure and increasing your turbochargers life.

[thre3kgt811]

so am i getting this right...the best exhaust upgrade for a stock SL would be to just get the testpipe and gut the pre-cats??? i really dont wanna lose any low end power taht would suck but i did want a little louder of a sound..so would guttin the precats and gettin a test pipe be the best way to do this?? would i lose any low end power doin this? thanks

[Hotshot8792]

losing low end power is just a myth, some people claim that it feels that way, but there shouldn't be any reason why, especially with the butterflies in the intake plenum, the whole purpose behind it is for low end power. But yea, get a test pipe. As far as precats, gut them if you have them. 91-93 cars don't have them, 94-95s some have them some dont, all 96+ cars have precats. If you have a 94 or 95, just look behind your intake manifold to see if you have an extra pipe coming off the back that goes to an EGR valve, if you have the EGR valve then your car has precats, if you dont see an extra pipe coming off the back, then your car does not have them.

[Musashi3000GT]

Hotshot, you've got a turbo (which I envy) but thats why you dont loose low end power. Us n/a guys do loose low end by opening up the exhaust! its not just a myth chief, I have seen the dyno charts and before the cat back I had 198 ft-lbs. of tourque at 4500 rpms, a month later I had the 2.5 inch cat-back and 185 ft-lbs of tourque at 4800 rpms. so yes, I did gain hp up around 6500 rpms but low end dropped slightly. I dont have a testpipe, my cat is intact so I posted the "loss of low end power" thread to see what other people thought. apparently no one has dynoed a base or SL stock and then after cat-back, test pipe, and down pipes. I will eventually order the test pipe and see how much more the low end drops, if its like 5 or 6 more hp down low then who care but if I end up with like 178 ft-lbs of tourque @ 4850 rpms then you guys will see bid up for it on e-bay.