so...just wondering what would work better...2 1/2 inch or 3 inch exhaust, i wanna make it flow a lil better, but i also wanna keep that back pressure, just wondering what anyone on here did and how they liked their results...i have 09 turbo ss...so anyhelp would be appreciated..

 

3" hahn exhaust

 

research more. you want 3" and want no backpressure..its a turbo not a supercharger.

 

im getting it custom...theres a guy down here that has done all my cars...so im gonna let him play with this one as well...lol....

you wanna keep a lil backpressure...having none at all would end up throwing tourqe away

 

car comes stock w/ 2.5

3" for it not to be a waste of cash, you don't need additional back pressure when you have a turbo

 

leave the stocker on, it flows real well, unless you want it louder

morgan at snyapse said they took the dp loose from the catback and saw no improvement, and i also saw on here about the stocker flowing 590cfm, so the restriction is in the catted dp not the catback.

 

^^^^^QTF, get a catless downpipe or get a highflow cat and downpipe, synapse has one of the best for the ss/tc so far. Don't forget either, if u want true gains from these mods you gotta tune it

 

yes,catless dp from synapse is awesome. im gonna get full 3'' straight pipe

 

Downpipe is the real performance bottleneck. Depends a lot on your goals. If you eventual plan on lots of mods and especially if you are considering a turbo upgrade, then big exhaust is a plus. If you are only planning few minor mods, then a 3" catback is probably not needed.

 

Yeah im goin with the ADM Full exhaust with a catless downpipe. With our setups you want no backpressure at all. So its 3" all the way through for me

 

go with hahn 3''''

 

all this you dont gain power from a catback is bs you do gain power by going 3in instead of stock

 

and the guy that said you want backpressure on your car because otherwise you are losing torque needs to be shot. It's a turbocharged car. Backpressure=bad on turbocharge car. The turbocharger provides all the backpressure you need

 

this is completely wrong, backpressure = bad, and you don't want it. old ricer myth. if you understood what backpressure is, you would understand why you don't want it.

that being said, you'll be better off with a 3".

 

The turbo will provide enough back pressure (well not really back pressure but you guys know what im talking about) Go 3''

 

sigh.... you don't want backpressure. doesn't matter turbo, super, na, whatever.

 

The back pressure thing is indeed bogus, but exhaust pipe size can affect exhaust gas velocity. You obviously can go too big which decreases velocity. I don't know how big too big is though. Seems like Hahn had good luck with their 3" catback, but for a nearly stock car, it's probably overkill.

 

All QFT. Back pressure is bad - but most people who talk about back pressure are really talking about exhaust gas velocity. However, after the turbo exhaust gas velocity doesn't matter - so larger is always better. On an N/A or supercharged, if you go too large, the exhaust velocity drops, which greatly affects EG scavenging, which affects how quickly the gases can exit. Too large, you get no scavenging effect, meaning the engine has to force all the gas out on its own. Too small, you lose power since you cannot push out the gasses fast enough. Scavenging acts as a vacuum that sucks exhaust gasses out faster than just pushing them out with the piston..

However for a Turbo, since we have that great big fan stuck in the exhaust flow, the largest pipe you can fit from the turbo back is the way to go.

 

synapse is a good pipe but they made a rookie mistake by putting the o2 censor on the bottom and it doesn't allow the moisture in the exhaust to drain so the Hahn dp I think is far more superior imo

 

The stock catback exhaust flows 470 cfm( the resonator is the most restrictive part of the catback) and the muffler flows 580 cfm. The most the stock turbo is cabable of inhaling is just over 400 cfm. The most restrictive thing on the exhaust is the DP it flows less than 300 cfm so it is the bottle neck. You will gain up to 15 whp by changing out the stock downpipe. I cannot imagine gaining more than 2-3 whp by changing the stock catback out. Does anyone have a dyno graph showing the gains of a 3" catback on an already tuned car?

 

3''

/endthread

 

go big or go home 3 inch