Need Help!! Custom exhaust Pipe

[CANMP3]

I have already done searches on this topic but I cant seem to find the answer I need, so I appologise for asking a question that has probably been asked many times before.

I would like to put on a custom exhaust. I would like 2.25 inch piping. If I remove the 2nd cat will that make any lights come on or will it cause any problems with mazda. I live in canada so there are no emmissions tests. Also is the bigger pipe thing (you can tell I dont know much about this topic) I think it is the resonator, can this come off as well. I would also probably get a new muffler too.

The reason I want it is of course I would like to add a little more hp, whether it be very little or alot(i wish), and also I would like a more aggressive sound to the car.

Should I do this or should I go with the bosal cat back?

Any Help would be appreciated,
thanks
chris

 

[NC_MP3]

If you remove the 2nd cat then yes, the check engine light will come on. You can get a custom exhaust and remove the cat and resonator if you want, it won't hurt anything. It may be a little loud if you remove the resonator, depends on the muffler though. You won't get much power from changing the exhaust, maybe 1 WHP. I would go with the Bosal cat back if you want a better sound.

 

[JcsMP3]

How is removing the second cat going to put the check engine light on. I didnt' see any O2 sensors before or after teh 2nd cat.....

If their are no sensors then nothing will happen with your check engine light.

Jc

 

[MP3-Owner]

NO Your Check Engine Light WILL NOT come on if you remove the second cat and resonator. I have the Bosal which does both and no lights at all.
As JcsMP3 stated...there are no O2 Sensors in the second cat, only the first cat has them.

 

[peter]

so our cars only have 1 O2 sensor?

also, is replacing the first cat with a high-flow cat (a carsound cat is my personal choice) going to trigger a CEL?

on my previous car (MY01 subaru impreza 2.5RS), high-flow cats would trigger CELs because the exhaust gas wasn't "hot enough" before hitting the cat(s). people tried wrapping the headers, still didn't work.

any input? thanks.

peter

 

[mazdamp3_18]

well ive got a 2.25 inch custom exhaust with my 2nd cat and resonator removed and i have no light and if you want to hear what it sounds like there are videos in the photo's and video section

 

[Traveler]

Our cars have what is called a 'close coupled' 1st cat. There is an O2 sensor right before the cat in the exhaust manifold outlet flange, and one right after the cat in the short manifold that turns and goes under the motor. The are both multiple wire heated O2 sensors. If you were to go to a high flow 1st cat it would have to be under the car and would necessitate moving both O2 sensors and extending the harnesses. Since they are heated I can't see why this wouldn't work, but no one has tested it yet. Also, if you remove the 2nd cat there is no other sensor in the exhaust anywhere near it so you won't throw a CEL.

 

[peter]

okay, i see. but why can't i put a high-flow cat in the first cat location?

thanks!

peter

 

[big_ben]

It won't bolt up to the manifold. Take the heat shield off the manifold and take a look at it. You will see why. You can take the guts out like I did though, that will throw the CEL. But you can mod the wiring to make it go away.

 

[peter]

okay . . . i was interested in just purchasing a universal cat from carsound and having it directly replace the stock 1st cat. is that possible, or is the first cat a strange size? (haven't taken the heat shield off yet.)

peter

 

[big_ben]

You can't do it. It is possible but it will cost at least $100 or more to get a flange made to match the manifold. That would be a waste of money and time. The O2 sensor mod takes about 30 minutes and costs about $4.

 

[peter]

i can't use the flange off the stock cat?

(ain't i a pain in the ass? )

peter

 

[big_ben]

No, the stock cat is made of cast iron. I have no idea why. But you cant weld steel to cast iron, not to mention you cant weld cast iron withough problems with leaking unless you know what you are doing. The first cat is easy to take off and drill out the internals.

 

[peter]

cast iron?! s***.

looks like i'll be relocating the cat, then. where can i get those O2 sensor mod for under $4?

thanks!

peter

 

[big_ben]

O2 mod
You can get al the parts from radio shack. You can make it on a pc board. It's very easy, just follow the drawing.

 

[NC_MP3]

So there are no O2 sensors at the 2nd cat. Man, shows how much I pay attention hehe.

 

[big_ben]

There is an O2 sensor on the manifold before the first cat, and one on the cast iron pipe right after the first cat. That's all. After working on my turbo last weekend, I saw that installing the header and modifying it to make it fit would be SO easy. If you have a welder and minor skills, it can be done very quickly. If I were putting a header on my car it might take half a day to get everything completely done. That's how easy it looks.