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catalyic converter

2K views 6 replies 4 participants last post by  kxiong2016 
#1 ·
i just install the greddy cat back exhaust and its still not so loud
does anyone recommend cutting the resonator/catalytic converter and put like a test pipe?
 
#2 ·
Hey there,

Lets talk for a moment about your goals. Why do you want you car to be loud? Do you care if louder means LESS HORSEPOWER? and what is your intended use? Daily driver, track car only? and last question are you tuning for your new exhaust?

Those are all important questions to answer if we are going to talk about upgrading your exhaust system.

If you want loud look int the gymkahna exhaust from crawford. its essenitally just a trumpet from the CAT backwards. Very loud and very raw. Keep in mind that in order to make more power to go with the new noise maker you will need to tune your ECU to handle the changes in airflow.

One last note, please dont go removing your CAT, the performance that the CAT costs is well worth the ability to breath when you get out of your car in the garage. High flow CATs work great and they wont impede your performance much with a proper tune.
 
#3 ·
Keep in mind that in order to make more power to go with the new noise maker you will need to tune your ECU to handle the changes in airflow.
+1

Also another note about all of that: if you remove too much restriction in exhaust and/or intake you may start to run into issues (depending on your year and engine size) with the Wastegate not able to remove enough air to control the boost resulting in boost spikes and overboost issues that could get as bad as fuel cut (on a regular basis in higher gears).

I fought that issue for a long while, starting with EBCS and extensive tuning but it was a HUGE pain in the ass to tune out and the compromise was that I had to basically underboost during spoolup and force the turbo to "catch up" later, resulting in unreliable, fluctuating, weaker boost. In the end an External Wastegeate was the only thing to solve my issue (aside from welding a new cat to re-introduce the restriction).
 
#4 ·
hi, thank you for replying. my car is a 2012 wrx sedan
I only want a little louder because i love the rumbling noise. I am satisfy with the noise when i step on the gas but when i dont put any gas in the car is quiet.
I bought the greddy cat back because I don't want it too loud but I guess its still quiet.
And I wouldn't want to lose power.
i don't go to track or anything with the car, just daily driving
as far as tuning for the exhaust, i didn't know tuning the car after install a catback would make difference
And if there is bigger issues taking out the cat, I will just leave it in there, I just heard people telling me that cat converter is causing my car to not be as loud so i just thought if i take it out will there be any issue. would my check engine light be on?
should i get a after market cat converter? is there such a thing? or just get a down pipe and up pipe? what will an short ram intake do?
please give me some advice, i appreciate it thank you
 
#5 ·
Actually surprisingly on my car gutting the cat did not cause a check engine light (yet) but I have the ability to simply disable the code when (if) that comes.

The problem is that the cat is actually in the downpipe... that's why a "cat-back exhaust" is called that, it goes after the catalytic converter.

Modifying the downpipe does require tuning and it will certainly change how your turbo responds to your engine.

If you're looking for more noise, even a catted aftermarket downpipe would give you a lot more sound. Also I believe my oem downpipe came with 2 cats if I remember correctly and aftermarkets usually come with one high flow cat that's less restrictive.

The "easier, softer way" would be to get an Accessport cable or Taxtrix cable (the Tactrix is advanced and will require you to learn a LOT of stuff about your car's ECU).... and an off the shelf Stage 2 map (and a downpipe designed to work with it).

Good luck!
 
#6 ·
You don't need a tune for a cat-back exhaust. Now if it was a Turbo-Back then it would be recommended to take advantage of it. And at times you would see Boost spikes but usually you can solve that issue by not dropping a gear rapidly to then hit WOT and easing into a gear to go WOT should limit the amount/remove the chance of boost spikes.

Want raw noise? Just do a muffler delete axle back. That should tickle your fancy. Its not as loud as a full exhaust with no cats but it will put out some noise.
 
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