cmlsweetc

okay so right now i have a custom 2.25" exhaust from the cat back. i had it ran just like the ark performance exhaust and im wondering what the stock exhaust size is for our cars (i was told it was 2" by the exhaust shop) just to make sure i did indeed increase my exhaust flow. i know agency power makes a 2.25" exhaust but i need some reassurance on my purchase. also should i replace the stock s-pipe and delete the cat? will it be really raspy without the cat and can i expect any power gain from changing these without aftermarket headers? another option is just having a high flow cat put in or running without one completely and keeping the stock s-pipe. im just unsure of what the best way to go is. i noticed a decent gain from both my cat back and injen cold air intake so im hoping a 2.25" s-pipe and/or deleted cat will net me some gains as well. thanks for all the input and advice.

SoccerBoy_AP

If your in Cali I don't recommend getting rid of either your header or your s-pipe.

However if you can still meet your states emission requirements, changing out the s-pipe is a good way to find maybe 7-10hp, by removing a choke point for your exhaust. The Invidia s-pipe is 60mm/2.36in in diameter, it mates up cleanly with the stock exhaust system. You will notice some added rasp but not nearly as much as if you change the header.

I am running a Alphawerks header (w/ Jet-Hot), Invidia s-pipe, and custom pipework with a high flow cat and one resinator back to two Magnaflow mufflers. I meet Colorado state emissions with that setup.

If you want to run a higher diameter piping, I'd go turbo or supercharger first, then you could jump up to 3" to allow for better flow of the extra boost you are generating. Jump from 2.25 to 2.5 in N/A applications isn't guarenteed to improve power.

my06tc

iTrader: (2)

you wont get any rasp by changing out the downpipe aka s-pipe it just frees up the exhaust flow makes the exhaust a little bit louder and deeper,only thing that makes the exhaust raspy is the header,thats when you get a cat or a good resantor,but it also depends on the muffler you have also,

KyleL

Yes, the original is 2". an s-pipe will also free up some exhaust flow with out causing rasp.

cmlsweetc

i went from stock (2") to 2.25" which ive been told is perfect for a N/A setup. this tc wont be seeing boost, im looking to build it N/A since it is a challenge and no one else has really done it. i can expect to see maybe 7-10hp though? im located in NC so emissions isnt a huge concern so ill probably replace the s-pipe and remove the secondary cat completely. will a 2.25" s-pipe mate up nicely to where it meets the header? oh, i dont have any resonators and im running a borla muffler for those who are wondering. thanks again for all the input guys, yall are the best.

cmlsweetc

anyone else who has some advice on this, feel free to post. it would be greatly appreciated. thanks guys

3min3m2

The s-pipe really is a choke point in the exhaust, especially for boosted. I ran a megan(which is for sale,cheap, PM me) for about 60k, and it was a nice addition. Had header and exhuast, could tell difference adding in the S-pipe.

cmlsweetc

thanks for the advice man. ive heard that it is a bad choke point in our exhaust but i wasnt sure if i'd feel a difference with my stock header..other than the header the rest of my exhaust system is custom (Injen cold air intake and 2.25" catback exhaust) so i should feel a decent gain just from adding the s-pipe right?

SciMeiji

I would go with the 2.5" invidia s-pipe. Reason being, the outlet for our stock header is 2.5". To say the stock s-pipe is a choke point, well thats an understatement. It starts out at 2.5" then it funnels down to 2" and then back to 2.25" as it meets the midpipe. Now dont get me wrong, megans 2.25" s-pipe is an improvement but why not go with a 2.5". It can only help as it will improve flow give u slightly higher power gains and make ur car more "FI ready" if u choose to boost.

cmlsweetc

well i have to go 2.25" since my exhaust is 2.25" from the cat back so i kinda want to keep that uniform throughout plus i have a fear of losing too much back pressure and actually killing my power gains.

scionmike06

+1

cmlsweetc

okay so i have just been informed by toyota that our s-pipe is where the o2 sensor is located, im not sure they're entirely right. i thought it was right after the primary cat in the header but again, i havent really looked. they also said i would need the secondary cat to pass inspection? he did say if it was inspected at toyota i would need it but im not entirely sure about this. if anyone has any clarification or help with this or any other portion of this post, please feel free to leave something. thanks again for all the help guys

SciMeiji

They are entirely right. U have 2 o2 sensors. 1 in the pre-cat on the header, and 1 in the s-pipe. If ur getting a raspy aftermarket header Installed make sure u buy the anti fouler for o2 sensor in the s-pipe or ull throw a CEL. If ur gonna stick with the stock header and go with an aftermarket s-pipe, no anti fouler is needed.

cmlsweetc

okay good, im sticking with the stock header right now but what you're saying is even though there is a second o2 sensor in the s-pipe, i wont throw a cel by removing it and the one in the pre-cat is the only one that matters as far as the cel is concerned?

uhsentc

g** d*** it with the technology and all the sensors in our car.

so the stock header doesn't act as a choke point for the exhaust system?

uhsentc

so something like this?
http://www.customcarscentral.com/inv...-scion-tc.html
with the antifouler?

cmlsweetc

it is a choke point but what they're saying is that the s-pipe is one of the worst choke points in our car's exhaust system. all of it can be improved upon though. the invidia s-pipe you posted a link to is exactly what im leaning towards. i was going to get it done custom but im not sure.