Straight pipe Piggies w/stock exhaust ?'s

[sCeRaXn]

Well i did my piggies yesterday, but havent put them back in yet(car is down for clutch install). I was assuming that the stock dp's were 2 1/4", but it turns out theyre 2". So i was trying to figure out ways to increase flow without hurting driveability(ie:codes) and without causing the car to sound horrible. I have some 2" stainless piping from another project, and i was thinking about replacing the main cats as well. I know removing both sets of cats WILL throw an 02 code, but could some anti-foulers get me by until i get a chip that can disable the code? I can make the anti-foulers myself, so this wont cost me anything. Also, will this sound horrible on the stock exhaust? It seems like it will be raspy, but i was hoping the monsterous mid-muffler will help kill some of that. I did a search, but there are so many posts about piggies that it would take me a week to find what i need to know lol.

Ive got some "big" plans for my piggies in the future...but that will have to wait until i get a chip and the material to make my exhaust. Lets just say itll be something new(from what ive seen anyway) and should add some really nice power while still sounding nice and deep. The straight pipe piggie idea is just a temporary thing.

[sCeRaXn]

OK ill break it down into two simple questions. Will anti-foulers keep the 02 code from popping up with straight pipes? Will this make my exhaust sound like ass? lol

[dc878mmm]

I am waiting to do a stg 3 clutch job on my car sp I can install the a custom exh and dp's all at once with (electronic exh bypass valves/aka open dumps). While I was waiting, I bought the car with the main muffler removed (I know, kinda ghetto) and I recently took the cats off to see how much hp I can get. The result is that it is loud as hell (which I don't mind so much) and sounds kinda like shit (which I do mind). Remember, this is with stock dp's. I do however still have the mid muffler or resonator on, so it is similar to your setup. BTW, I used non-foulers and the CEL kept coming back.

IMO, open dumps are one of the best ideas in addition to a good exh so you can sound good and have a little back pressure during daily driving, and have an option to completely bypass your exh at the touch of a switch. When you hit that switch, it won't sound good but it'll be the best way to free up a whole lot of horsepower at the flip of a switch.

[sCeRaXn]

I was afraid that it would sound like shit. Oh well, ill just leave the main cats on for now. After i get a chip im going to build my own exhaust, which will start with the re-worked piggies. Im planning on cutting the "bulge"(pre-cat) where it reduces to 2.5"...then running 2.5" piping from there back. Itll run into two high flow Bassani cats(which i already have) and then to a dual 2.5" in/out muffler. It should sound mean and still flow enough for a decent amount of power without throwing any codes. And if thats too loud ill merge the two 2.5" pipes after the cats, and run 3" from there to a 3" inlet/dual 2.5" outlet muffler. From my experience, this will quiet things down a little bit and still flow really well.

[mholme]

Not sure you realized or not, but you are going to throw cat efficiencey codes if you remove the pre-cats. The O2 sensors only measure the pre-cats, no sensors behind the main cats unless you relocate the secondary O2 sensors there. Or use anti foulers in the secondary O2 position.

[Jung]

yeah you leave your primary o2s alone, you throw the CELiminators on the main cat 02's... idk if this will help but i gutted my rear stock muffler (drilled a nice huge hole inthe back of it, removed the shit inside of it), but had it with stock dps/cats... sounded deeper, like an r32 exhaust

[mholme]

yeah you leave your primary o2s alone, you throw the CELiminators on the main cat 02's...

No O2's on the main cats..They both read the pre-cat, upstream and downstream. I'm guessing you mean put the celiminators on the secondary O2's(downstream)?

[sCeRaXn]

Not sure you realized or not, but you are going to throw cat efficiencey codes if you remove the pre-cats. The O2 sensors only measure the pre-cats, no sensors behind the main cats unless you relocate the secondary O2 sensors there. Or use anti foulers in the secondary O2 position.

The 02's will be moved behind the main cats. The original question was about anti-foulers keeping the code from popping up with straight pipes...but ive decided that im not gonna do that now. Im just gonna leave it like it is until i decide to do the "super piggies" lol

The only reason i was thinking about doing straight pipes is because the dp's were out of the car anyway, so i might as well do as much as i can to them. However, i despise raspy exhausts and would rather sacrafice power than have a shitty exhaust note.