3" exhausts...

[blackeclipse]

I plan on getting a 3" magnaflow exhaust, no cat, and 02 eliminator downpipe. Now my question is do I have to get new manifold/turbo and everything to put on a 3" exhaust system or how does it all hook together when things aren't the same size. It's probably a newbie question so post any links that already explain this. Thanks.

My other question is will a 3" exhaust have any negative effects on a pretty much stock system or will it be fine?

 

[nanokpsi]

It will be a staight up remove and replace. I would leave the stock 02 housing attached to the stock downpipe when you remove it as the bolts on the end are usually pretty frozen. Everyhting will run fine and you will notice a nice performance increase. I would take the heatsields off first, drie the car to heat it up and then spray liquid wrench on the bolts you want to take off. Lett it cool a little and then have at it. I didn't feel like searching and making a rude reply telling you to do the same. See, some of us are nice to newbs

 

[phatTSi]

The only thing you might want to worry about it boost creep with a 3'' system. But you can port out the wastegate to help prevent this. The liquid wrench is a very good idea also i used it when removing my exhaust manifold and they broke loose very easily when it came time to do it.

 

[Omega]

3" will be overkill, 2.5" is fine. You will lose some ground clearance and have creep issues. I should have gone with the 2.5 system.

 

[ProjectTalon130]

3" will be overkill, 2.5" is fine. You will lose some ground clearance and have creep issues. I should have gone with the 2.5 system.

It really depends on the Turbo, that's what it all comes down to really....I do agree , 2.5 is plenty for daily use and some races here and there...3" is ideal if you have BIG plans for the car such as in my case.

 

[00 Agent]

It really depends on the Turbo, that's what it all comes down to really....I do agree , 2.5 is plenty for daily use and some races here and there...3" is ideal if you have BIG plans for the car such as in my case.

Even if you don't have BIG plans a 3" exhaust will still be better performance wise. On a turbo car the more flow the better. Even on an otherwise stock car a 3" exhaust will outperform a 2.5". Like it was mentioned with a FULL 3" exhaust you will have boost creep problems, porting the wastegate and O2 housing will help but not always eliminate it. To take care of it completely get an external wastegate or run a 2.5" downpipe and 3" downpipe-back exhaust.

 

[TSIfreek]

I agree that it all depends on the turbo you have really. The only problem with the 3" down pipe is that you will have boost creep unless you go to an external WG. Alot of guys dont realize this and they find they are creeping 4 psi at the top end getting knock with a 3"DP. If you have a 50 trim go with 3" but 16g's stay with 2.5" down pipe
I would go with porting your O2 housing and turbo housing/WG, 2.5" stainless DP, TEST PIPE, and 3" cat back. This is a tryed and true system that will get you even get you in the 11s. I would go stainless because it kepps the heat in the system that incresses exhaust speed/scavenging

 

[blackeclipse]

I would go with porting your O2 housing and turbo housing/WG, 2.5" stainless DP, TEST PIPE, and 3" cat back.

What all do I have to buy to do that and do the 2.5" pieces hook up perfectly to the 3" pieces or what do I put between them?

 

[TSIfreek]

There are adaptors that companys make for the 2.5"to the 3.0". Just ask the company that you get the cat back from to make you one. APEX N1 and thermal come with adaptors. What ever company down pipe you decide on going with make sure to ask them the cat back that you want will mount up to the flanges at the correct angle.

 

[Omega]

You are going the wrong way with the dia. Buy the 3" downpipe and cat, then neck it down to 2.5"

You want to keep the velocity up when the exhaust leaves the turbo (3") then when it cools, decrease the dia so it speeds up (2.5")

Don't worry about a 3" downpipe causing creep alone. It's the whole free flowing exhaust that does it. The slightly more restrictive 2.5" cat back will be fine.

 

[TSIfreek]

You are going the wrong way with the dia. Buy the 3" downpipe and cat, then neck it down to 2.5"

You want to keep the velocity up when the exhaust leaves the turbo (3") then when it cools, decrease the dia so it speeds up (2.5")

Don't worry about a 3" downpipe causing creep alone. It's the whole free flowing exhaust that does it. The slightly more restrictive 2.5" cat back will be fine.

OMEGA were did you come up with that
Gas volume is not the same as velocity. When you increase the volume of anything the velocity/speed decreses. WTF is a 3" down pipe into a 2.5 cat back going to do? it causes a restiction. Who cares aout how hot the gas is at that piont.

 

[blitz43]

OMEGA were did you come up with that
Gas volume is not the same as velocity. When you increase the volume of anything the velocity/speed decreses. WTF is a 3" down pipe into a 2.5 cat back going to do? it causes a restiction. Who cares aout how hot the gas is at that piont.

ok lemme get this str8t

wat set up is better and won't cause boost creep...

3" downpipe 3" hi flo cat or test pipe 3" cat-back

2.5" downpipe 3" hi flo cat or test pipe 3" cat-back

or

2.5" downpipe 2.5" hi flo cat or test pipe 3" cat-back

which is better?

 

[TSIfreek]

2.5 DP, 2.5 test pipe. 3.0 catback

 

[bigfoot]

You are going the wrong way with the dia. Buy the 3" downpipe and cat, then neck it down to 2.5"

You want to keep the velocity up when the exhaust leaves the turbo (3") then when it cools, decrease the dia so it speeds up (2.5")

Don't worry about a 3" downpipe causing creep alone. It's the whole free flowing exhaust that does it. The slightly more restrictive 2.5" cat back will be fine.

On a N/A car that needs a bit of back pressure maybe, but turbo cars have too much already so we need a free flowing exhaust.

 

[reese]

i have a 3 inch down pipe (Andersen High Performance 195.00)with no cat and a custom 3inch mandrel bent exhaust to a generic 3in inlet 3in outlet muffler(custom work siad and done 150.00). then it proceeds into 2in twin tips. and all tucked away nice behind the talon stock ground effects.

at first it was creeping real fu_ckin bad.


so i i got a 2g ported 02 housing off the trader for 30 bucks.

problem solved.....now i realize that not every car will have the same results as mine....i guess its a fluke

anyways when i get my new SBR shortblock installed i also just bought a 2g ported exh manni.....so i will have some serious fu_ckin exhaust flow!
so my free flowing exhausdt setup with no creep on the 14b at 15psi cost me about $425(as much as a name brand cat back)
my .02 cents

 

[blackeclipse]

thanx u guys. 2.5" to 3" it is.

 

[blitz43]

but when its time for emissions would i fail because i have a test pipe?

 

[bigfoot]

I made an alternate center section using my stock cat. I'll bolt it in on test day.

 

[blackeclipse]

but when its time for emissions would i fail because i have a test pipe?

Glad I live in Idaho where we don't have emissions tests yet.

 

[DSMeclipse4G63]

2.5 into 3 would be ideal gradual increase in size... the reason people creep is because their exhaust is very high flowing and the restrictive o2 housing all the sudden looses back pressure causing a surge in exhaust flow...go 2.5into 3in and port your stock o2. Oh and 2.5in full exhaust is good for any t28 variant or 16g lvl turbos...in other words with the right car 2.5 can get into the 11s. good luck
Andrew