Thread: GXP Exhaust. Ordering parts but have questions

ok so heres what im fixing to order for sure. My intentions with my exhaust are to make it a little louder and allow the engine to flow better as im pretty sure the stock restricts it alot.




so a the first of my exhaust questions to come is the exhaust pipe the runs from the DP to the Y split is 2.5" (im pretty sure) then from the Y split it goes down to 2" to the mufflers. now with the new DP will i need to replace all the exhaust pipe to a larger size? like the same size as the DP, or should i use this and not get an 02 bung on the DP and use the one on this



I am also going to do a resonator delete and straight pipe that section. for mufflers i am not completely for sure where to start on these...so many different types. like the offset and where the inlet and outlet is located. Would this one work and sound good?

Flowmaster 40 Series™ Delta Flow 942041 - Muffler | O'Reilly Auto Parts
edit: flowmasters....rulled out for now looking for something better thats not as crappy.

now for the type of tips i should get...i dont want expensive and i also dont mind to have to clean them every now and then. but i know im going to have to replace the stock ones so if anyone has any suggestions or ones for sale please let me know.

any other exhaust stuff or links i should read as well let me know. ive been reading alot of em on here but none have good specifics that im looking for so i can order

The donwpipe should bolt straight up to the factory cat-back.

Are you planning on running a cat? How are you going to deal with a code if you don't run one?

For mufflers, get under your car and see where the pipe enters the rear of the muffler, that will tell you what offset you will need to buy.

Performance difference is none.

Gas Mileage difference is something you will see without a cat and no tune. The code P0420 will set and cause the car to use extra fuel to see if it can get the rear o2 to read what it wants, but it never can. So with a tune, it can be worked around.

Hmmm I may add the CAT to the zzp DP cause it probably won't be until march time frame when I'm ready for him to start tuning. What about the pipe from the DP to the tips? Will I be fine leaving all that stock sizes except for removing resonator and changing mufflers and tips?

edit: i just updated the original post up there and added the CAT in to the DP.
also what about the exhaust reducer that zzp has listed i posted up there

I would leave it all the same size and just have the mufflers cut and welded on there. They really is no reason to replace the whole exhaust because you dont gain anything.

Why not just invest in a set of headers. Doug Thorley offers a set. I also believe Cal Speed Perfomance is making a set. There is plenty of info over at ls1tech.

I agree, headers or no deal.

The headers for these cars are way over prices and for the money just don't do enpugh. But please let's keep on topic here from my original post. As for the engine mount question...it still has two.

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None of the mufflers will make the sound you are looking for. The crossover design makes it sound the way it does. The Flowmaster 40 series is going to be loud and cause drone inside the cabin.

Honestly, sounds like a cutout is what would suit your budget and sound wants.

Personally I would get Magnaflows for the Gxp...Flowmasters 40s are just to loud and drone like crazy. Magnaflows will increase your tone slightly compared to stock.

If its a 3800 = Borla. LS = Magnaflows.

Originally Posted by marines542

hmmm i dont want it super loud. but i want it more noticeable. from what ive read the exhaust on the gxp's restrict flow a lot. how much louder is a cutout and does it make any performance gains? i do know for sure that i'm going to do a new ZZP DP.

Yes a cutout will be loud, but the benefit is being able to close it when you factory sound. As far as performance it will be like running open headers so there is a gain there especially when it comes to a LS based engine. You are only talking about maybe spending 50ish dollars with install. So it's not like you are losing a whole lot if you decide you don't like it.