question on what to replace on exhaust system

[bigtom9492]

hey guys, i'm looking to replace my exhaust system and i'm wondering what exactly i need to replace. would my cat be okay to leave on and just replace the cat back? or should i replace the downpipe, cat and cat back. That's where i'm a little confused. how many parts are in the 99 gpgt exhaust system. It goes headers to downpipe to cat to cat back correct? Thanks for the help guys

 

[Scottydoggs]

the cat is in the down pipe then theres a resonator, then the intermediate pipe, aka Y pipe to the mufflers.

if you have all stock cat back, that means its all welded together, so you need a welder to replace individual parts.

if its after market and all clamped together, you can drop the cat back and change mufflers, or the res. cat is still welded in the dp in most cases.

 

[bigtom9492]

it is indeed all stock so i would need to replace the downpipe and then get a cat back correct?

 

[Scottydoggs]

if your cat is still good, you can have the U bend deleted at a shop, then replace the cat back with what ever system you like.

or get a new catted DP.

 

[bigtom9492]

okay sounds good, thanks for the help man. :th_thumb-up:

 

[cavell]

We replaced the entire systems on 2 different Gtp cars. Both were modded with chips,pulley, intake and so on. 1 had new cat and 1 had no cat. Than we sold both cars. New owners liked new systems. Made zero diff in performance and sure did cost a lot. Oh, the systems we took off were fine. No rust. Wish I would have kept at least 1 for car #3 or 4. Those muffs did rust out. Figures.

 

[Scottydoggs]

We replaced the entire systems on 2 different Gtp cars. Both were modded with chips,pulley, intake and so on. 1 had new cat and 1 had no cat. Than we sold both cars. New owners liked new systems. Made zero diff in performance and sure did cost a lot. Oh, the systems we took off were fine. No rust. Wish I would have kept at least 1 for car #3 or 4. Those muffs did rust out. Figures.

did you say "chips" installed, what a waste of money, if you thought the cat backs cost a pretty penny, you just wasted what ever on a chip, they are all fake and do nothing.

 

[cavell]

we bought both cars with mods. tuned pcm, pulley, intakes, but both had stock exhaust. we replaced exhaust on car #1 and it ran the same, before and after. sure sounded different though. car was FAST. easily beat my caddy. than we sold it. got car #2. same mods, same stock exhaust. so we replace that exhaust and no difference in performance either. that car was 7/8 as quick as car #1. i could feel it being slightly slower. sold that too. we actually sold both cars for what we had paid plus parts so we never lost money. kid likes to screw around with modding cars and than sell them. we put all new sound systems in both cars. subs, amps, HU, that stuff. buyer #1 liked system so we threw it in. buyer #2 did not care for it so we yanked it out.

 

[Slick2500]

OP unless the catback is rusted out leave it be, all you are going to do is make it sound worse. Best money is spent on replacing the restrictive manifolds and downpipe/ubend.

 

[nik12937]

I think the problem is that you're focusing on the catback. The restrictions are almost entirely before the cat.

Throw some headers on either car, and you'll most likely see a big difference. A pulley drop without headers will give you lots of KR, and a lot of reduced timing, which will actually make the car slower over all.

This is assuming you have stock exhaust manifolds, we don't have headers stock.

Edit: From what I've heard, our stock catback is good until about 300-350whp.