# PROS & CONS FOR HOLLOWING OUT THE CAT??



## BurnZ_240sx (May 1, 2004)

wassup everyone... by experience, can you guys help me witht the pros and cons for hollowing out the cat??? because i wana hollow out my cat but i wana make sure its worth it not to mention im one of those guys that are way low on money  

any advice is apperciated
Thanks!


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## pete? (Jul 6, 2004)

hey man dont do that. thats bad for the envi. not to mention you live in cali so theres no way you could get away with it. also your exhaust will sound like hell. not sure about the s13 but on my car the HP gains are so minamal the effort it takes to punch it out isnt worth it.


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## dj42000_2000 (Oct 19, 2004)

The only thing that would make punching the cat out worth it is if it is completely clogged. Dropping it can take some effort due to rust buildup and you could damage your exhaust more than you fix it. If you think your cat is clogged, buy another one. I know that costs money, but so does the gas you are spending on a clogged exhaust.

truman
peace


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## BurnZ_240sx (May 1, 2004)

whew!, im glad i asked befored "tryed" haha... 

yea, my cat isnt clogged, well atleast not that bad to the point of replacement... so i guess my next step is to save!... thats hard for me heh!

Thanks for the Advice guys!


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## B11sleeper (Oct 15, 2003)

if you had a car that was running way rich and for some reason you didn't want to fix it and wanted to avoid a under car fire, I suppose you might want to remove it.

There doesn't seem to be any reason to take a working cat out of the system.


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## Kato (Apr 21, 2004)

As bad as it is for the environment, I hate to say it, but a gutted or test pipe actually gives you pretty good gains...you'll be able to feel the difference, especially at higher RPMs...get a legal high flow cat...


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## sciroccosven (Dec 1, 2004)

Kato said:


> As bad as it is for the environment, I hate to say it, but a gutted or test pipe actually gives you pretty good gains...you'll be able to feel the difference, especially at higher RPMs...get a legal high flow cat...


dont gut your cat, it will make a hollow metal opening in your exhaust system and wont resonate very well. If you are you to take the time to do that go buy some quality stainless hardware and have someone weld you a good stainless test pipe for ease of swapping when inspection and emissions come around. My advice, dont screw with it.


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## Joel (Jun 11, 2003)

a punched cat is a $10,000 fine here in Oz


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## Slydin240 (May 20, 2004)

WOW $10,000 is alot. I'm glad I live in Ohio, we have no inspections.


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## BurnZ_240sx (May 1, 2004)

Slydin240 said:


> WOW $10,000 is alot. I'm glad I live in Ohio, we have no inspections.


i know really 10,000.. talk about saving the rain forest... out in cali i never heard of someone getting sited for a gutted out cat... but i guess thats just me..


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## JayLew (Sep 15, 2002)

sciroccosven said:


> dont gut your cat, it will make a hollow metal opening in your exhaust system and wont resonate very well.


On a N/A car that statement is true. But on a car running a T25 it actually is almost undetectable......and it sounds really good at WOT.


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## Marblecake (Jun 19, 2004)

Remember alot of smaller cars need the back pressure fromt he cat. I have seen alot of cars run worse with a hollowed or no cat.


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## Fonnybone (Jul 18, 2004)

As the owner of a 1990 240SX SE with a pipe welded to the exhaust (money 
considerations mostly...exhaust was falling to pieces so i replaced all but cat)
i can say, it sounds terrible. I found the 240's exhaust way too soft and 
mellow before, after it was intrusive and boomy. Oh wait, i think i also skipped
the resonator, hehe, that would explain the boomy part. The catless sound
is when you release the throttle and you hear this crackling sound. Not very
nice sounding either. 

As for power 'increase', i have to stop now and laugh. Haha, hahahah, hahah,
hehe, ehhhh no. Nothing there. I wasn't expecting any power gain either to 
be honest. I think the 240SX is just laggy by nature. If you want an example,
try to press the throttle slowly instead of flooring it, i fell an honest butt-o-
meter measured 5hp right there. I've read quite a few people talk about better
throttle response with an after-market chip. Sometimes i miss my old V-dub 
Scirocco 'cause i could just pop the hood and twist the distributor instead


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## sciroccosven (Dec 1, 2004)

Fonnybone said:


> As the owner of a 1990 240SX SE with a pipe welded to the exhaust (money
> considerations mostly...exhaust was falling to pieces so i replaced all but cat)
> i can say, it sounds terrible. I found the 240's exhaust way too soft and
> mellow before, after it was intrusive and boomy. Oh wait, i think i also skipped
> ...


lol, yeah i know what you mean. Anytime you get rid of a cat or a cast manifold on a N/A car your going to get more noise and its not going to be as pleasant. Believe me, i know from experience. I have a 16v scirocco with a eurosport race header which eliminates the cat (which is why they call it a race header) and a 2 1/4 exhaust with a cherry bomb brand turbo muffler. The muffler weighs next to nothing but it is also a piece of crap that doesnt muffle or do anything for that matter and i have alot of popping off throttle. actually its non stop off throttle and i also have the popping on throttle. Anytime you are allowing that much freedom in your exhaust with little or no sound restriction there will be unpleasant sounds but the higher rpm power gains will be maximized. On a 240 with either early or later model 2.4 your main objective should be focused elsewere because your going to take more so much of your torque away that your acceleration isnt going to be affected. 
Turbo charged cars like jay mentioned will almost always sound smooth on an engine like the 240's. The turbo smoothes and quiets the exhaust tone as the engines sounds get immediately thrashed and spun through the turbine and housing and sent out the back with a truley awesome sound. If you have a turbo charger and are not afraid of emissions or fines then GET RID OF YOUR CAT. It just creates positive pressure in the manifold at high boost levels. Im running around 16lbs in my audi with my tiny k03 turbo and i probably have around 2 lbs of pressure just from gases that cant go through the cat fast enough. 
My advice to those with N/A 240's without alot of work done is that you could more effectively screw with your car by A/C removal, scraping sound deadening, removing spare tire and tools, seating or any other garbage that you dont use that adds weight or is an accesory that is run off your engine. Removing non mechanical parts doesnt affect your emmisions, it doesnt make your car sound like a kazoo, it wont prevent you from passing emmisions/inspections, and its enviro freindly, not that you or i really care though. So hopefully this will help anyone that does a search for hollowed cats or reads this. Or is just bored like me. Im done.


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## BurnZ_240sx (May 1, 2004)

Its pretty funny, i was the one talking about hollowing out my cat, but from researching, and alot of friends advice, (i DID NOT) hollow the cat, i got a test pipe instead... anyways, i started from the guard (ofcourse) of the cat.. the first two screws on one side snapped off  (damn rust) the other two on the opposite side came off fine, (guard is off)... now for the cat.. 4 bolts, *easy to take off* power tools maybe (hand work) not a chance (well for me anyways).. the damn bolts wouldnt even budge... there were times where i put the wrench on the bolt and tried hammering it to make it lose, negative... didnt work either... so after about 45 on 1 damn bolt i said nevermind.. i can wait for some power tools, the next day driving on the free way i heard my cat getting louder, finally it got so loud to where i stopped at the gas station to check it... at the time it was dark so i couldnt see, went home and checked the next day at work.. THE PIPING FROM THE CAT TO THE RESANATOR JUST SNAPPED... WTF in the world happend... im assuming from banning the wrench with the hammer... did something to the piping cause all the damn rust.. i dunno but it was pretty funny, sounds like shit... but now.. i midest well get a whole new piping system...


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## 240droptop (Nov 28, 2004)

BurnZ_240sx said:


> Its pretty funny, i was the one talking about hollowing out my cat, but from researching, and alot of friends advice, (i DID NOT) hollow the cat, i got a test pipe instead... anyways, i started from the guard (ofcourse) of the cat.. the first two screws on one side snapped off  (damn rust) the other two on the opposite side came off fine, (guard is off)... now for the cat.. 4 bolts, *easy to take off* power tools maybe (hand work) not a chance (well for me anyways).. the damn bolts wouldnt even budge... there were times where i put the wrench on the bolt and tried hammering it to make it lose, negative... didnt work either... so after about 45 on 1 damn bolt i said nevermind.. i can wait for some power tools, the next day driving on the free way i heard my cat getting louder, finally it got so loud to where i stopped at the gas station to check it... at the time it was dark so i couldnt see, went home and checked the next day at work.. THE PIPING FROM THE CAT TO THE RESANATOR JUST SNAPPED... WTF in the world happend... im assuming from banning the wrench with the hammer... did something to the piping cause all the damn rust.. i dunno but it was pretty funny, sounds like shit... but now.. i midest well get a whole new piping system...



WD-40 is your freind plus using a strong arm would have helped I've changed numerous exshsausts cats etc etc power tools arnt neede infact they don;t usaly fit


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## 240droptop (Nov 28, 2004)

haha god i'ma m idiot I went inot the thread knowing it was old and still i posted


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## slideways240sx (Feb 19, 2005)

I actually liek the way mine sounds alot without a cat and a magnaflwo muffler the 2.4s are a pretty raspy lil mother dont sound to bad when u let em breath a lil bit LOUD but not to bad soundin


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## RichthePoser (Apr 8, 2005)

Easy thing to remember when people bring up the "changes in exhaust tube ID makes you lose horsepower/tq" is theres nothing like having a solid 6" thick wafer mounted in the tubing to rob performance.

Rich


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