Exaust Piping question

[flipnoy213]

Would it be bad on my GST to have a
stock downpipe --- 3" CAT ---- 2.75" cat back
or
3" downpipe --- 3" CAT ---- 2.75"cat back


Because my future plans are to change my downpipe, and cat. i already have 2.75" cat back, i heard its better for all my pipe diameters to be consistent. 2.75" Downpipe---2.75" CAT---2.75" Cat Back

 

[oddrob]

Always try to go smaller to larger.

 

[Eagletalon2fst4]

just make sure you still have back pressure

 

[Spln_Hrd]

just make sure you still have back pressure

not to knock on you but with a turbo you don't really need back pressure in your exhaust after the turbo. it will make enough for you.

i would recomend smaller to larger. but 2.75 might not make that much of a diff.

maybe try to sell yours and pick up a used 3"

 

[97jestergst]

why dont you go with a 2.75" and and 3" or even test pipe so every thing matches up and you just get the higher flow you were looking for with the 3" cat, thats the way id go atleast or even what you coud do is if you get a bigger down gow with the 3" and pick up a greddy STYLE cat back on ebay you can get the whole set up as cheap as 200 buck! thats what i DID good luck
-jester

 

[flipnoy213]

So i should be going 2.75 to 3" in stead of all 2.75? Whats the reason behind this?

 

[97jestergst]

the .25" isnt gonna make that much of a difference so instead of putting out the money for redoing ur exhaust in 3" get a high flow 3" cat and keep all the 2.75" shit you already got n spend the extra money on other mods this way all ur exhaust matches up at 2.75" and you get the high flow you need thru the cat and you get great flo with out having to put out the money for new exhaust you see?

 

[Burnett03]

the .25" isnt gonna make that much of a difference so instead of putting out the money for redoing ur exhaust in 3" get a high flow 3" cat and keep all the 2.75" shit you already got n spend the extra money on other mods this way all ur exhaust matches up at 2.75" and you get the high flow you need thru the cat and you get great flo with out having to put out the money for new exhaust you see?

a bottleneck is a bottleneck no matter on size.. its bad either way.

 

[flipnoy213]

a bottleneck is a bottleneck no matter on size.. its bad either way.

So consistent 2.75 the best way?

 

[kikkinbac]

I have always heard that 3 inch is the best for a turbo. Unless you have a HUGE turbo and you need to flow ALOT of air go bigger. Also backpressure on turbos is not needed. N/A cars need backpressure. I would say if you plan on making some good size numbers just bite the bullet and buy 3 inch turbo back. Also if your in a non emissions regulated area like I am go with a straight pipe. If your not and you got some extra cash buy both a cat and a straight pipe and just switch them out when the clean air man comes a calling. In the end you will be happier knowing that that .25 bottle neck isn't holding back those couple extra ponies you want .

 

[flipnoy213]

Is this bad because it might bottle neck? A downpipe with inlet of 3" and outlet of 2.75", this should match my 2.75 cat back. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7979724342&category=33633

or
should i get the downpipe that 2.25 inlet and 2.75 outlet?
http://cgi.ebay.com/ebaymotors/ws/e...=7979365453&rd=1&sspagename=STRK:MEWA:IT&rd=1

 

[flipnoy213]