What to expect with a new exhaust?

[jgouds]

Hi all,
I understand that bench dyno-ing is frowned upon but I've done several searches that lead me to asking this question. I am upgrading my more or less stock exhaust (only things changed are test-pipe instead of cat and 2.5" downpipe) to a 3" Apexi N1 turbo back (downpipe, test pipe and catback). While I've seen tons of questions about how much horsepower this will add (tons of crazy estimates) I see very little discussion about how this will affect the rest of my car -
With the extra horsepower made will I have to add extra fuel?
Should I turn my MBC down after installing the exhaust?
Is this just unlocking power that's already there or actually adding power?

Mods so far are : evo III big 16g, 560cc injectors, moates ostrich with tunerpro RT, K&N filter, FMIC, aftermarket cams (unfortunately no idea which ones), boost gauge, AEM wideband, gm 3" maf, maf-t, MBC, wally 190LPH pump.
Hope that's all relevant - any help/input is appreciated

 

[crimsondragon]

Unlocking power that's already there. I changed nothing when I went to 3" from stock. Did notice improvement but everything settings wise stayed the same.

 

[jgouds]

Wonderful - that's good to hear. Big difference? It seems like all I've read are mixed reviews on how awesome or not upgrading your exhaust is

 

[curt-s]

Depends on how restrictive it was in the beginning -- no way to tell that. If you want real answers, dyno with each back-to-back. Maybe a dead squirrel in there is causing a quarter of the flow it should be capable of.

You will not have to change anything when you switch to a different exhaust, unless somehow it manages to unlock massive power and shifts you into an efficiency where your supporting modifications are no longer able to keep up because the power is so powerful. Is it possible? Sure, I guess. Is it likely or even remotely likely? No. Unless the aforementioned dead squirrel clause holds true.

On second thought, you could have an entire family of dead rodents in there and it still wouldn't matter.

 

[NY 95 TSI AWD]

Get ready for some higher boost because a full 3 inch exhaust is going to make that 16g creep.

 

[jgouds]

Glad to hear it - car is running fine now so I can't imagine there's many dead animals hanging around the important bits. I'll put it on and report back. Thanks for the input[DOUBLEPOST=1407449906][/DOUBLEPOST]I forgot to mention, turbo and o2 housing have been ported. Think the o2 porting will stave off the boost creep?

 

[NY 95 TSI AWD]

A lot of times porting the turbo will cure boost creep, but some people have worse luck. You'll just need to wait and see.

 

[yamaripper415]

When I ported mine it didn't help with the creep so I went external waste gate.. so much better control.. but the exhause will definitely open things upespecially if your looking for mor power down the road.

 

[cheapracer]

Just from a seat of the pants point of view, when I upgraded to 3", there was a noticeable improvement. Turbo spool up was much faster after.

 

[jgouds]

Well installed it yesterday. Holy wow - big difference. Works awesome, thanks for the advice guys.

 

[MitsuRu]

Running 3" here loving it need my downpipe next can't wait.