Knocking out the cat

[X_budha_X]

I am going to knock out the internals on my GF's cat, i was just wondering if any one could tell me if there is a big difference in the sound, its a 95 240 SE:thinker

[bruinbear714]

I knocked out the internals on my GF's cat too... the cat squeeled for a few seconds until all the blood gushed out then it was dead quiet.

[Aries]

um... that's nice...

Now, a cat with no internals will be noticably louder, but no so much as to be obnoxious. Just be forewarned that there will be a difference in sound, and the SES light may come on due to low/no backpressure.

[sixxdeuce]

You might get a really annoying sound at certain rpm's, I was told it was from combustion inside the hollow cat, but a pipe welded through the cat so everything is a constant diameter fixed the problem

[Frankie1Eighty]

i heard knockin out the internals ain't always good performance wise, due to the fact that you could mess up the air flow. Could be wrong though , can anyone correct me?

[I am Technoman]

Knocking out your kat is not a good idea. And dos'nt get you anywere when it comes to hp gains.

[Dano]

my cat is completely stripped, it came that way when i bought it...it was the only mod done to the car i guess, cuz the engine was 100% untouched. i also have n1 dual on the car and its not very loud at all, i was a little dissapointed in the sound actually after installin the n1 dual, but if i got headers itd be louder...hehe..

-Dan

[X_budha_X]

all i ended up knocking out was one loose plate, there isnt any really noticable sound difference. oh... and the reason i did it at all wasnt for performance it was to stop this G** D*** RATTLING that was driving me crazy. no light by the way either.... at least not yet

[X_budha_X]

do you really think tha the one plate will really affect the back preasure that much? i didnt take out all of the internals.

[bruinbear714]

Whoa hold yer horse there. That rattling is your heat shields.

[X_budha_X]

it wasnt the heat sheild, the nissan dealer said the cat was fallin appart.... so after i did it the rattle was gone

problem solved....

[nnkfws333]

Well other than making the car louder.......it will pollute the environment as well. They were sorta put on a car for a reason.

[X_budha_X]

i only removed A SINGLE PLATE, NOT ALL OF THE INTERNALS

[nismo240]

i really don't think you should gut out the whole insides of the cat.. just make you a hole straight through about 1 to 2" round in diameter... because i heard that if you gut the whole inside ...the car seems to bog down and hesitate.. due to no restiction for the air...

[daniel240]

There are 2 cats on my 96 240sx. i installed the hs header and that replaced the 1st cat. this made the car much louder. later on i stripped out the second cat. i did not notice a difference in noise our h/p. i think that the first cat makes a big difference. if you dont have headers, you might try this cat. ( its the cat bolted on right after the manifold) i dont know if the older 240's are like this though.

[I am Technoman]

There are 2 cats on my 96 240sx. i installed the hs header and that replaced the 1st cat. this made the car much louder. later on i stripped out the second cat. i did not notice a difference in noise our h/p. i think that the first cat makes a big difference. if you dont have headers, you might try this cat. ( its the cat bolted on right after the manifold) i dont know if the older 240's are like this though.

Is your car auto? I think the auto 240's have two real kats. I dont know why! Removing your kat or gutting it will couse you to lose a fair amount of torque.

[daniel240]

no my car is a manual

[I am Technoman]

HuMMM I wonder why some s14's have 2 kat's and some just have one?

[daniel240]

i think it has to do w were they came from. i know some from cali. that have 2 kat's too..

[hotshot240sx]

i just straight piped...no cat at all...the sound probably got alil rougher...but back pressure is a problem...causes my light to come on....and makes my 240 run richer...but its noticable...so make shure you have a bit of back pressure...makes a world of a difference

[I am Technoman]

i just straight piped...no cat at all...the sound probably got alil rougher...but back pressure is a problem...causes my light to come on....and makes my 240 run richer...but its noticable...so make shure you have a bit of back pressure...makes a world of a difference

This is the reson I decided to stay with 2 1/4 inch back piping as opposed to 2 1/2 or 3. My HS header is 2 1/2 at the collector then I have the expation chaimber then 2 1/4 so the flow is allways fast moving.

[Nismoking]

Do the 91-94 HS headers end up 2-1/4 at the flange, cause I was considering one if I ever get my handson a 240, and plan to do a cusotm exhaust aswell. If it is, I will do the 2-1/4 inch piping to, cause it makes since, and there won't be a pressure drop I guess?

Do 91-94 240 fastbacks have 2 cats, and what should u upgrade them with for more flow w/ the header. Also is their a kae out of the 2, that doesn't need to be upgrade, or should I replace it too?

Thanks,Chris

[cleets-s13]

not all 240's from 91-94 have 2 cats. mine doens't. it just has one about a foot from the collector. i've removed cats from a couple of my six past cars and never noticed a drop in torque, as long as you have your muffler on the end and the pipe is sealed and there are no holes in the pipe, the sound is louder but smooth, and theres enough backpressure to keep your torque up.

[aspinballer]

my 95 has a resonator then the cat then muffler.dropped the first two completely replaced it with a pipe.the car breathes deeper and saves me gas as well as sounds great

[cory2081]

my 96 SE had 2 cats. with the header, i just have 1. knocking out the internals of the cat will cause turbulance min the exhaust system. Get a downpipe that eliminates that upper cat (closest to the manifold) Thats the best thing to do besideds getting a header

[whoflungpoo]

I just put a HS header on my 95 manual(production date of 94) IT only had 1 cat and a dummy container for the second one.

I'm thinking of putting a High flow cat in, just incase i ever need to get smogged, but the HS and the N1 catback is pretty nice.

[cory2081]

Yeah, I have the HS and Apexi N1 single. Sounds great!! My car is a 96 (built late 95) and my second cat is not a dummy. Kinda weird how some are and some arent. I just left mine in place, it's loud enough as it is and I'm sure it flows plenty for my current setup.

[whoflungpoo]

I believe mine is an OBD1... it's hard to tell, I opened up the hood side by side with my wifes 97, and hers had a lot of extra piping snaking across the intake manifold, and her second cat was functional. I also haven't found the OBDII reader socket on my 95 either. the only thing that makes me thing it could be OBDII at all is the presence of the second O2 sensor...

I too like the sound of mine, but it gets a little raspy for my taste towards the high RPM, i'm guessing it's the absence of my cat.

[96_240sxSE]

my 96 SE has two cats. i've been meaning to swap out the pre-cat (as someone i crossed paths with referred to it as such), the one closest to the manifold, with a downpipe. trying to wait until after my smog though as i'm assuming this is not smog legal??! ;p

anyhow...my greddy headers and catback don't give me TOO much sound...just enough...and i'm good with that! =)

[Jookmasta]

blew out all the internals of my cat with a delightful backfire. nothin but a hollow shell now. no issues or signals that flare up