3" or 2.5" turbo back?

[TsiOcr]

i am getting an EvoIII big 16g and was wondering if i should get a 3" turbo back or if 2.5" would be plenty? Is there That big of a HP difference from 2.5 to 3" ?

 

[greyforestgst]

2.5 is fine for that turbo

just make sure its mandrel bent, and also get a test pipe

 

[jbillakdsm]

2.5" will do the job with no problem. You won't notice a big performance gain going to 3", but you will notice a gain in noise as you drive down the street.

 

[Cirus_93TSI]

if u plan on keeping ur car nearly bone stock with that 16g at low boost a 2.5 might be ok, but if ur planing on getting more work done and running around (or over) 20 psi i would get the 3"
everyone iv ever known who has gotten a 2.5" exhaust on a turbo car has taken it off and sold it to buy a 3" because they werent happy with the 2.5, its a huge waste of money to get a 2.5 when u know 9 months from now when u get some more upgrades ur going to wish u had gotten the 3"
iv got a 3" turbo back on my car and i still have the stock 14b, it makes plenty of power and i know i have plenty of room for more upgrades and i wolnt need a bigger exhaust any time soon, and its really not all that loud, my friend has a 2.5 on his 2g when he bought it and when he got rid of that for the 3" it really didnt make it much louder, although the exhaust tone is much deeper and sounds alot better with the 3"

 

[doug]

2.5" is fine.

 

[DSM-KiD4g63]

hmmm i always wondered the same, but in cali i wanna be legal, so 2.5 with a test pipe aint gonna happen, so would a 3' with hi-flow be about the same as a 2.5 with test pipe?

 

[johnnytsi]

Go 3", I installed the 2.5" system on my car a year and a half ago and have now converted to a full 3" turbo back setup I had the exhaust shop set up a 3" free-flow cat, build me a test pipe and used a N1 style muffler. They welded flanges on everything so I can easily remove the cat/test pipe. With the cat in place the car has a deap low growl that is not quite loud enough to draw unwanted attention. With the test pipe the exhaust is definately loud enough to draw attention. My seat of the pants impression is that the 3" setup with cat flows just as well as the 2.5" system with no cat (test pipe installed).

 

[jdmawd]

Originally posted by jbillakdsm
3", you will notice a gain in noise as you drive down the street.

Simply not true, my car is much quieter then any 2.5" system that I have ever heard on a dsm off boost. Im Also quite sure my system is a much better example of a *true* 3" exhaust then most. I have no reduced sections in the exhaust anywhere. My 02 is 3" my d/p is 3" (no 2.5" neck) and my cat back is 3"

 

[doug]

Originally posted by jdmawd
Im Also quite sure my system is a much better example of a *true* 3" exhaust then most.

jdm, did you go straight to that 3" system from stock, or did you have some other aftermarket exhaust before your current one? I'm still researching the whole 2.5" vs 3" thing...

 

[jdmawd]

Originally posted by doug

jdm, did you go straight to that 3" system from stock, or did you have some other aftermarket exhaust before your current one? I'm still researching the whole 2.5" vs 3" thing...

I went from stock to 3", but all the parts were not available at once. I did the cat back first then when the d/p shipped i installed the d/p and test pipe what a difference that made

 

[loreak]

i have a 2.5 and im ditching it for a 3 inch....get 3 off the bat, its a turbo car, they love big exhaust

 

[vertGST]

here comes doug
edit: i guess i am a little late
Brendon

 

[MNGSX]

Sound level has alot more to it than pipe diameter.

High Flow cat VS test pipe.

Muffler construction and type, Canister VS Oval. ETC...


I'd go 3".

I have even bigger in place on my car but it depends on where you are going with the car.

 

[TsiOcr]

what do you guys think about the downpipe from www.exhaustdepot.com
it has a 2.5" neck and then the rest is 3" its all stainless steel and it eliminates the cat for only $180. will i be losing a lot of power because of the 2.5 neck instead of total 3"?

 

[MNGSX]

No you wont loose much. I noticed that it is'nt just a short section but up to the flex. If it were only the first 6-10" of the pipe that were 2.5" it would have even lower losses.

Unless you go to a tubular 02 housing the housing is'nt bigger than 2.5" any way.

I'd get a tublar o2 housing and it's mating downpipe plus I high flow cat if I were you. But as far as having a 2.5" tube where it bolts to a passage about that size why would it hurt there?

 

[pickens]

go 3" press bent. I just did my exhaust and I was going to go 2.5" when I looked at the press bend on 2.5" it looked really small. So then I was going to have them do mandrel 2.5" bends, but when they told me the price I said, screw that, just give a 3" press bent. I love it now! It sounds nice and deep, but not loud at all. I would've regreted getting the 2.5"

 

[gvr4in]

Originally posted by pickens
go 3" press bent. I just did my exhaust and I was going to go 2.5" when I looked at the press bend on 2.5" it looked really small. So then I was going to have them do mandrel 2.5" bends, but when they told me the price I said, screw that, just give a 3" press bent. I love it now! It sounds nice and deep, but not loud at all. I would've regreted getting the 2.5"

For how much restriction press bends put out, its just like having a 2.5 system mandrel bent.

I CANNOT believe you just suggested he buys a press bent system!

Go 3" Mandrel Bent turboback.. You'll be a very happy camper

 

[jbillakdsm]

I remember reading somewhere that a 3" press-bent flows about the same as a 2.5" mandrel-bent system. I still don't understand how people think 3" systems right off the bat are goin got help. Everyone I know that put a 3" system on without a good number of motor mods has boost creep out the wazzoo.

 

[gvr4in]

Originally posted by jbillakdsm
I remember reading somewhere that a 3" press-bent flows about the same as a 2.5" mandrel-bent system

I swore I just said that.

Going 3" Is going to free up ALOT of restriction, ridding boost creep is all about having the ideal o2 housing, turbine housing and exhaust manifold.

 

[Cirus_93TSI]

if its necks down in the middle somewhere (3" to 2.5" to 3") its going to be crap and ur going to lose power, it its 2.5" at the o2 and 3" at the cat it will be fine, thats how my downpipe is, 2.5" at the stock 02 and 3" from about halfway through the downpipe all the way back(all mandral bent of corse), it was like that when i bought it but i dont have any complaints, it feels and sounds just as good as the extreme 3" turbo back on my friends 2g
and press bent is nothing but garbage, if ur going to spend money on an exhaust do it right and get it manderal bent, a 2.5" manderal bent with a cat will probally flow as good if not better then that 3" press bent junk with a test pipe, espicaly with all the bends that are involved with ur cat back bending to go under ur rear axel on our cars, get manderal bent or u will end up buying one and getting rid of the press bent sooner or later, whenever u realize how muc power ur losing
just get the 3"manderal bent right off the bat and save urself the trouble of wasting money having to get a 3" manderal bent after u realze ur not happy with the junk u bought

 

[Sotarts]

Originally posted by Cirus_93TSI
if its necks down in the middle somewhere (3" to 2.5" to 3") its going to be crap and ur going to lose power, it its 2.5" at the o2 and 3" at the cat it will be fine, thats how my downpipe is, 2.5" at the stock 02 and 3" from about halfway through the downpipe all the way back(all mandral bent of corse), it was like that when i bought it but i dont have any complaints, it feels and sounds just as good as the extreme 3" turbo back on my friends 2g
and press bent is nothing but garbage, if ur going to spend money on an exhaust do it right and get it manderal bent, a 2.5" manderal bent with a cat will probally flow as good if not better then that 3" press bent junk with a test pipe, espicaly with all the bends that are involved with ur cat back bending to go under ur rear axel on our cars, get manderal bent or u will end up buying one and getting rid of the press bent sooner or later, whenever u realize how muc power ur losing
just get the 3"manderal bent right off the bat and save urself the trouble of wasting money having to get a 3" manderal bent after u realze ur not happy with the junk u bought

STFU. and it's 'mandrel.

First determine if you'll ever outflow 2.5" system.
Port the crap out of waste gate passage and upgrade the flapper for the bigger passage if you're going to go with full 3" system.

2.5" and 3" cats have the same core, except larger end-tanks when it comes to 3".

If you do research and decide that you will not modify your car beyond outflowing 2.5" inch system, get a 3" press-bent with a 3" cat. Period.

 

[doug]

Originally posted by aovsi
First determine if you'll ever outflow 2.5" system.

I totally agree.

Originally posted by aovsi
If you do research and decide that you will not modify your car beyond outflowing 2.5" inch system, get a 3" press-bent with a 3" cat. Period.

If you're not gonna outflow a 2.5" system, why wouldn't it be better to just get a good 2.5" mandrel system instead of a 3" press-bent? It'll be quieter, not hang as low, and flow (and perform) as good as a 3" press.

 

[DeezNutsForYou]

I have the downpipe from exhaustdepot.com and I like it alot. I don't have much to compare it to, because I went straight from stock to this. It is 2.5 mandrel to the flex. The flex is 3" and the rest is 3" until it connencts to the cat, then it comes down to a 2.5. I was so pissed when I saw that, because their site doesn't say anything about it going back to a 2.5. So when I had my 3" press bent put on I just had him cut that part and do it completely 3".

 

[Sotarts]

Originally posted by doug

I totally agree.

If you're not gonna outflow a 2.5" system, why wouldn't it be better to just get a good 2.5" mandrel system instead of a 3" press-bent? It'll be quieter, not hang as low, and flow (and perform) as good as a 3" press.

Yeah, but the idea of 3", even if pressbent, the pipes will fit the 3" inlet/outlet diameter cat. And might actually flow teeny-weeny bit more, insignificant probably though.

Like I pointed out in previous post, 2.5" cat and 3" cat have same core, except 3" actually has larger inlet/outlet pipe diameter, which will flow a bit better.

 

[Knuckles2.0]

well spending 500-800 bucks on an exhaust sounds fun and all but what about building your own 3" exhaust with say a dynaflow at the end... any one have any luck with that ??