New to the Turbo game.... (EJ255 exhaust)

[LunchBox04V]

Hey folks. Well I just became the owner of a shiny new (to me) 2005 GT sedan. Starting to retrofit parts already. Lol I'm looking at replacing much of the original exhaust system. I also have some concerns on pipe diameters with my planned mods. Here is what I found:
Original:
Headers - up pipe with cat - turbo - downpipe with cat(2.5") - mid section with cat (2.5") - resonator (2.5" in, 2.25" out) - Y pipe - 1.5" piping to factory mufflers.

Planned:(up pipe cat removed to protect turbo... Guess 2005s up cat would breakdown over time and damage the turbo)
Headers - Invidia up pipe (without cat) - turbo - Perrin down pipe with hi flow cat and mid pipe (3") - 2.5" from mid pipe to resonator - 2.25" vibrant resonator (in and out) - 2.5" Y pipe to mufflers - magnaflows (haven't figured which ones yet, 3" in).

In the mod I had a few questions....
1) would the 2.25" resonator overly restrict flow? (basically waisting all the other work because it is the smallest point in the new set up)
2) would running the current (original) downpipe and cat waste the other mods down stream?

Any other tips or suggestions would be greatly helped. I have never had a turbo car before so I'm trying to learn fast. Thanks for any tips.

[Garrison]

Hey folks. Well I just became the owner of a shiny new (to me) 2005 GT sedan. Starting to retrofit parts already. Lol I'm looking at replacing much of the original exhaust system. I also have some concerns on pipe diameters with my planned mods. Here is what I found:
Original:
Headers - up pipe with cat - turbo - downpipe with cat(2.5") - mid section with cat (2.5") - resonator (2.5" in, 2.25" out) - Y pipe - 1.5" piping to factory mufflers.

Planned:(up pipe cat removed to protect turbo... Guess 2005s up cat would breakdown over time and damage the turbo)
Headers - Invidia up pipe (without cat) - turbo - Perrin down pipe with hi flow cat and mid pipe (3") - 2.5" from mid pipe to resonator - 2.25" vibrant resonator (in and out) - 2.5" Y pipe to mufflers - magnaflows (haven't figured which ones yet, 3" in).

In the mod I had a few questions....
1) would the 2.25" resonator overly restrict flow? (basically waisting all the other work because it is the smallest point in the new set up)
2) would running the current (original) downpipe and cat waste the other mods down stream?

Any other tips or suggestions would be greatly helped. I have never had a turbo car before so I'm trying to learn fast. Thanks for any tips.


The smallest diameter in the exhaust pipe is the most restrictive place, and everything else behind it flows the same amount.

In other words, if your exhaust looks like this post-turbo: "3--->2.25"--->2.5"--->3"
Your flow will be ~ 2.25" worth; despite having larger piping behind it.

And to answer the other question, yes, 2.25" piping is choking your turbo.

[chuckthefuk]

Garrison is bang on.

1 & 2 are both bottle necks for the system.

3" from downpipe (including 3" hi-flow cat welded in) -> 3" mid-pipe -> 3" resonator -> 3" reducer Y-pipe to 2.5" -> 2.5" axle back(s) to your choice of 2.5" muffler with 3" tips...

Muffler Canisters "straight through" styles provide 0 back pressure with some resonance .. Baffled mufflers reduces the raspy sound but is more restrictive.

[LunchBox04V]

That's kinda what I thought. The only reason I was thinking of using the 2.25" resonator was because it was sitting around. lol already paid for and all. Lol ok, so what is the diameter of the factory downpipe? Im cool with running it for now if it's 2.5". I'll source a 2.5" Vibrant Ultra as well no matter what. Lol anyone looking for a 2.25" one?

[LunchBox04V]

Ok, well it looks like I'm going a little crazy. lol Never thought I would do it, but it looks like its going to be 3" from the turbo to the mufflers. I talked to the local shop and they said it was pretty much the same to them whether it was 2.5" or 3". I'm I being a little foolish here? So...

3" downpipe w/HF Cat. > 3" Midpipe > 3" Vibrant Ultra Resonator > 3" Y pipe > 3" muffler IN

Is that going to be crazy loud? I have done the crazy loud thing, and was hoping to have something that was comfortable at cruise, and fun when I want it. (Nothing like asking for hard data on a hypothetical... lol) I have heard the turbo quiets it down a lot, and the vibrant that I have on my BK did wonders for the raspy sound (2.25").

Thanks again.... I hate asking these "What if" questions....

[r3v_v3ng3]

As long as you have an oval muffler rather than the canister one, it will be quieter. They both offer straight thru on the oval and canister. All 3" piping is the way to go. My .02 cents

[LunchBox04V]

I was planning on using an oval muffler. I believe Magnaflow 14385 was the number. My guess is more dampening material? (I just don't think the round canister would look as good on this car, in my opinion)

[SilentRacer]

I have a full 3inch exhaust, it is not loud at all as long as there are no exhaust leaks. The only thing you should keep in mind is when you are mixing and matching components from different manufacturers, you are bound to run into fitment issues. The midpipe, y and mufflers should all be the same manufacturer in my opinion. It may be more expensive initially, but you will save on all the custom work the muffler shop will have to do to make it fit right.