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View Full Version : will it be too loud if i take my cat converter off?


tiger-jill
01-09-2005, 11:51 PM
i have an american thunder folwmaster system on it, but im thinking i will take it up to local shop have it taken off, then in two years when i need the inspection put it back on. what do u think. i have an 03`. will it be deafly loud? or just a little louder than what it is now?

ausie
01-10-2005, 07:01 AM
I do not believe that the cats will change the sound much. My car is almost as loud as running open headers and I have all 4 cats in place along with the stock iron manifolds. Considering what the SLP sounded like right after installation, that was almost ear piercing. Even the video did not provide the full sensation of audible sound only a taste of the tones. I know....the stock headers and cats are restrictive. There are alternatives to that. Unfortunately, there is a federal law that restricts shops from removing Cats unless they are found to be defective (based on 1975'ish mandates). I am not saying it cannot be done, but may be difficult to have a shop remove the cats. I could be wrong, some states may allow it.

The most restrictive parts of the exhaust system are the cast iron headers since you already changed the muffler section. Perhaps some long tube headers, a 2.8 inch pulley, a pair of high flow cats with an x-pipe (the cats can be removed in some kits and replaced with striaght pipe), and a new flash program will probably net you 115+ Hp (free flowing headers may reduce the peak torque numbers by 1 to 4 ft-lbs but the increase in Hp is worth it). It all depends on how much money you want to spend.

NewFoundPower
01-10-2005, 08:12 AM
And it won't be emissions legal either if you take the cats off.


-D-

blk04cobra1
01-10-2005, 08:29 AM
an x pipe w/out cats plus a cat-back system will definitely be loud, no matter what system you choose...but it also helps your motor breath a lot better and will make more sense once you start modding...

Firme
01-10-2005, 08:44 AM
no cats are DEFINITELY louder than having cats.

One solution for you is to get the Bassani mid pipe, it has a section where you can swap the cats in and out.

Here in TX you need cats to pass emissions, but they do an ODBII inspection on 96+ cars, and usually don't bother to do the visual inspections.

I do not believe that the cats will change the sound much. My car is almost as loud as running open headers and I have all 4 cats in place along with the stock iron manifolds. Considering what the SLP sounded like right after installation, that was almost ear piercing. Even the video did not provide the full sensation of audible sound only a taste of the tones. I know....the stock headers and cats are restrictive. There are alternatives to that. Unfortunately, there is a federal law that restricts shops from removing Cats unless they are found to be defective (based on 1975'ish mandates). I am not saying it cannot be done, but may be difficult to have a shop remove the cats. I could be wrong, some states may allow it.

The most restrictive parts of the exhaust system are the cast iron headers since you already changed the muffler section. Perhaps some long tube headers, a 2.8 inch pulley, a pair of high flow cats with an x-pipe (the cats can be removed in some kits and replaced with striaght pipe), and a new flash program will probably net you 115+ Hp (free flowing headers may reduce the peak torque numbers by 1 to 4 ft-lbs but the increase in Hp is worth it). It all depends on how much money you want to spend.

A couple of things to note here bro. For one, now it all makes sense to me hearing you say you still have your stock H. SLP loudmouth is the loudest most obnoxios cat-back I have heard this side of the FRPP 3" catback (No offense, just MHO), but on your car, sounds good. I think the reason "why" is because you still have the quiet stock H. The cars I hear down here with the SLP and offroad midpipe, you can hear poping n' gurling from over a mile away when they are WOT, and most people cover their ears when they are close. SLP truely captured the tractor sound of the FBODies with that catback, BUT, your configuration sound GOOOD. So you might want to do a little more comparisson before swappin anything else out on the exhaust.


Secondly, the 03/04's are different than previous year Cobra's. The mid pipe is a smaller restriction compared to the catback, and the stock headers, well sometimes I am convinced that they are just as good as some of the aftermarket (just cast iron and heavy). I have seen 03/04's dyno after a longtube install and gain 3 hp and lose tq (but to be fair they have some gains throughout the power band, but you gotta compare money spent vs. gain, and its not the best bang for the buck till you are heavily modified). I think you won't benefit from LT's unless you are pushing 500+rwhp.

Just my .02 :dunno:

Lthl Venom 03
01-10-2005, 09:31 AM
take em offfff! :thumbsup: :D

cobrabitn
01-10-2005, 10:05 PM
Once you remove the pipe for your catalytic converters, be prepared to hold your ears. It will be obnoxiously loud! (I love that :rotf: ) Talking on the cell may be a problem when cruising at highway speeds, not that I do that. :rolleyes:

However, if you want attention when you are running down the road, you are sure to get it by having an aftermarket catback and an OR pipe installed.

Good luck with whatever you do. :)

InfamousSVT
01-10-2005, 11:59 PM
You ask if it's going to be too loud without the cats!?

It can never be "TOO" loud!:D :D :D

ausie
01-11-2005, 07:20 AM
:eek: I was only giving an opinion. :D. In other words I do not think it would be too loud if you took the cats off. There are many good quality mid pipes out there such as Bassani, etc.... I can agree that they will be less restrictive than the stockers (and probably will not rust as quick as the factory components), I am also considering mid pipes down the road.


You are right, my mistake, LT headers not a good idea, I need to wipe the 01 from my mind. Call it a time slip :D I did not mean to go beyond the topic at hand.

tiger-jill
01-18-2005, 12:33 AM
okay so as of now i have an ameriacn thunder flowmaster system w/ a "h" pipe. what is the difference between a "x" & "h"? & since my "H" pipe is loud, but i want it louder, what can i add or subsitute to the system that i have to make it louder but yet cost efficient at the same time? or do i just take off the cat converter & keep the system that i am now sporting? oh all this jargin gives me a headache. what would i do w/out u guys??????? HELP I NEED IT TO BE AS LOUD AS A REAL RACE CAR. THAT IS MY DREAM.

InfamousSVT
01-18-2005, 12:38 AM
For cost effective change that will also add a great tone, take off the cats! You will need to get some MIL's for the rear two o2 sensors or just have a tuner (chip) turn them completely off! The difference between a H and X pipe is that the H pipe will give you a more deep tone. Since you are already running the Flowmaster mufflers, which are chambered, you want to run a H-pipe or Prochamber (MAC). The X-pipe will give it more of an exotic sound compared to the H-pipe.
Taking off the cats or just getting an off-road H-pipe will benefit you more in your search for sound!:thumbsup:

Good luck!

tiger-jill
01-18-2005, 12:56 AM
For cost effective change that will also add a great tone, take off the cats! You will need to get some MIL's for the rear two o2 sensors or just have a tuner (chip) turn them completely off! The difference between a H and X pipe is that the H pipe will give you a more deep tone. Since you are already running the Flowmaster mufflers, which are chambered, you want to run a H-pipe or Prochamber (MAC). The X-pipe will give it more of an exotic sound compared to the H-pipe.
Taking off the cats or just getting an off-road H-pipe will benefit you more in your search for sound!:thumbsup:

Good luck!

when u say "exotic" do u men that older 69' mustang sound? like the sound borla gets? a sleek pop, pop, pop sound? that sucks if your sayng yes because thats the sound i was trying to go for. thats what i get trying to be too much like a dude & thinkin i know it all. not that i dont know it all. i just dont know alot about muscle cars yet, but i`m learning. so the mils for rear o2 thingys...how much do those run? is this something you all can instruct me on installing or do i need to hire a man to do this>? i already have an "h" pipe. should i just buy the "x" pipe & trade it out? & can u just buy the "x" part of the pipe? im getting mixed answers on taking the cats off. some say it wont be that much louder, you say it will. why two diff answers? what is the difference between "off road h pipe" and a "normal h pipe" which is what im runnin now? im learnin, whew!!!

InfamousSVT
01-18-2005, 01:05 AM
Exotic like a Lamborghini. If you're going for the classic mustang sound, you want a H-pipe! You can buy an off-road H-pipe, which is a H-pipe without catalytic converters and the mil's just are a "plug-n-play" type of deal where you just plug one end into the o2 sensor and the other into the wire that you unplugged from the o2 sensor. The mil's run around $60 for the pair of them. They fool the cars computer into thinking that you have cats on it and are emissions legal, except for the visual inspections!
The X and H pipes run from the headers back to the cat-back and just bolt up to the flanges on the exhaust pipes!

tiger-jill
01-18-2005, 01:24 AM
does it send a signal to your car disabling any driving if the cats are off, is that why the "mils" are good? i heard from a friend at work that i have a computer chip in my car that will disable the car from running if it detects that the "earth" is beinf affected? is that true? does it really disesemble the car from runnin? is this something u guys can instruct me to do myself or do i need to take it to a shop? i would enjoy learning how to work on my car, but is it something that i could use as a starter to learn, or is it too complicated & could **** up some ****?

InfamousSVT
01-18-2005, 01:28 AM
The mil's will just keep your check engine light from coming on if you take off the cats! If your computer reads from the o2 sensors that you don't have cats on the car, the check engine light will come on and this won't disable your car, but it will affect the air/fuel ratio and the cars performance!
Yes, this is something that you are able to do yourself!

tiger-jill
01-18-2005, 05:44 AM
thanks for all info, i will probably private message u when im ready to do this. oh, where do i buy this $60 product? did u already tell me this?

ausie
01-18-2005, 07:12 AM
There is nothing like a good nasty rumble. That is probably one reason I have yet to change my mid pipe, but the benefits of the extra scavaging may be worth it. My guess would be to keep the old mid section for inspection purposes and go with the off road H pipe or X-pipe. Since in my area, it is mandatory to have emissions testing every year :( that would be a pain since the timming of the inspection occurs in the peak of the fun driving season (mid summer). My question would be, has any body passed emmissions testing with after market mid sections or tuned ECU's? I would guess most hold on to the factory parts and put them back in place for the dreaded sniffer test. I do know some of you are fortunate enough not to require emmissions testing at all. I guess I am missing all the fun since I have no idea the of the sound improvements without cats. :(

I guess Lambourgini or Ferarri sound is exhautic considering the V12's have a their own sound to them (they sound more like an in-line 6 toyota supra with a fart cannon). The same can be said for the V-10 Viper but at least it does not sound as cheap. American V8's will not sound that bad. However, the 4v V8 has more of a distinctive sound and probably will never sound like a 69 Boss 429 with a radical cam, but you may get close. Be cautious how loud you make it, in some areas they are mandating mufflers used at the track due to the ever growing housing developments close the fun zone. I heard they are closing Englishtown Raceway (NJ) just for that reason (too many residential complaints). That could be just a rumor running through the grapevine, I am dissappointed if they do close it since I have yet to get there.