I have a 04 si ep3, I just got a blackworks cat back system, and I just ordered a megan racing test pipe, will my car run when I eliminate the cat? what are the pros and cons of doing this with the stock ecu, until I can afford a piggy back and get it tuned.

 

You can run it but you will need to get a defouler for your secondary o2 sensor so it doesn't throw a Check Engine Light. Your car will be faster but it will also be louder and maybe a little raspier than normal. It could also make your car run a little lean, at least thats what happens when people add a race header to their car, a test pipe may be the same...

 

what is a defouler? I am trying build this car right, I dont want to go with cheap ****.

 

If you don't know what the defouler is, you need to go read this entire forum, Clubrsx, clubep3 and Ephatch forums before you go taking parts off your car.

 

lol irony using a blackworks catback and a megan test pipe.

Anyway, you need a "defouler" because your test pipe is going to replace where the cat (catalytic converter) is in stock form. The secondary oxygen sensor is on the car to detect that the cat is in working order. Since there will no longer be a cat, it will go !!! no cat !!! and a Check Engine Light will come on.

What the defouler does is it places the secondary oxygen sensor slightly away from the test pipe. Doing this allows the exhaust gases to slip into the oxygen sensor only a little bit and "tricks" the ECU (computer) to thinking a cat is still on the car.

Note: This is not a guarantee fix. You will likely have to reset your ECU/battery once in a while to keep tricking the ECU.

Defouler:

http://www.corsportusa.com/store/cat...02defouler.png

http://i273.photobucket.com/albums/j...7/defouler.jpg